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Book of Abstracts - Lehrstuhl und Institut für Wasserbau und ...

th

5 International Short Conference

on Applied Coastal Research

Book of Abstracts - SCACR 2011

th th

6 to 9 June 2011 in Aachen, Germany

Honouring Prof. Robert A. Dalrymple

Johns Hopkins University, Baltimore, United States


Organizing committee:

Sonja Christoph,

RWTH Aachen University, Germany

Guido Kaschel,

HTG, Germany

Andreas Kortenhaus,

TU Braunschweig, Germany

Rainer Lehfeldt,

GCERC-KFKI, Germany

Stefanie Lorke,

RWTH Aachen University, Germany

Stefan Schimmels,

Forschungszentrum Küste, Germany

Holger Schüttrumpf,

RWTH Aachen University, Germany

Giuseppe Roberto Tomasicchio,

University of Salento, Italy

Published by:

Institute of Hydraulic Engineering and Water Resources Management

RWTH Aachen University

Mies-van-der-Rohe-Strasse 1, 52056 Aachen, Germany

2011© Copyright is reserved by the authors.

RWTH Aachen University and University of Salento, the SCACR 2011 secretariat and the

SCACR 2011 local organizing committee do not bear responsibility for any statement or

opinion expressed in this book.

Except as otherwise expressly permitted under copyright law or RWTH Aachen University

Terms of Use, the content in this book may not be copied, reproduced, republished,

translated, posted, broadcast or transmitted in any way without first obtaining RWTH

Aachen University written permission or that of the copyright owner.

The conference was organized by:

The conference was sponsored by:


Book of Abstracts - Conference Program III

th

Monday 6 June 2011

13:30

14:15

14:30

16:00

16:15

16:30

17:00

17:15

17:30

17:45

18:00

18:15

18:30

Registration

Conference Opening

Holger Schüttrumpf

Giuseppe Roberto Tomasicchio

Technical Session 1 Coastal Structures

Chairman: Dr.-Ing. Rainer Lehfeldt

LECTURE 1: Design aspects of breakwaters and sea defences

Jentsje W. van der Meer

Modelling of turbulence fields in front of the rubble mound breakwater

Özgür Dumuş

Simulating porous breakwaters with OpenFOAM - a sensitivity analysis

Gerald Morgan

COFFEE BREAK

Effect of berm width on reshaped profile of berm breakwaters

Peyman Aghtouman

A hybrid modeling approach on floating breakwater dimensioning

Anja Brüning

Run-up over variable slope bottom. Validation for a fully nonlinear Boussinesq-type of model

Antonino Viviano

Wave run-up on dikes

Antje Bornschein

A probabilistic approach for run-up estimation

Giuseppe Barbaro

Effects of surf beat caused by long period swell on wave overtopping rate

on complex bathymetry

Hiroaki Kashima

Overtopping formula for vertical tiers-headed wall defences

Corrado Altomare

th

Tuesday 7 June 2011

Technical Session 2 Coastal Processes

Chairman: Dr.-Ing. Stefan Schimmels

09:00

10:30

10:45

11:00

LECTURE 2: Water waves: an overview from theory to models

Robert A. Dalrymple

A development of an estuarine hydrodynamic model in cylindrical coordinates

Luminita-Elena Boblea

Characterization of Hydrodynamics of a coastal lake system, Amapa, Brazil

Maria de Fátima Alves de Matos

COFFEE BREAK

th

5 SCACR


IV 5th International Short Conference on Applied Coastal Research - SCACR 2011

th

Tuesday 7 June 2011

Technical Session 2 Coastal Processes

Chairman: Dr.-Ing. Stefan Schimmels

11:30

11:45

12:00

12:15

12:30

12:45

13:00

14:15

15:45

16:00

16:15

16:30

16:45

17:00

17:15

17:30

17:45

A 2D morphodynamic-numerical model of the surf zone “Strand”

Peter Mewis

Long-term morphodynamic modeling of the German Bight – model set-up and validation

Frank Kösters

Sediment dynamics in a mangrove creek catchment

Erik Horstman

Steady streaming and sediment transport in the boundary layer at the bottom of sea waves

Paolo Blondeaux

One year evolution of two beach sectors at Cadiz littoral (SW Spain): storm impacts, erosion

processes and (no) recovery

Nelson Guillermo Rangel-Buitrago

Short-term simulation of the evolution of a curvilinear coast

Miguel Ortega Sánchez

LUNCH BREAK

Technical Session 3 Coastal Risk / Risk Management

Chairman: Prof. Ing. Giuseppe Roberto Tomasicchio

LECTURE 3: Intregrated management of coastal flooding risk and the European

Directive for flood risk assessment

Panayotis Prinos

Turbulent boundary layer under a solitary wave: a RANS model

Giovanna Vittori

Numerical and physical modelling of wave penetration in Oostende harbour

during severe storm conditions

Vincent Gruwez

COFFEE BREAK

Numerical simulation for indicator of vulnerability to climate change on four French beaches

Philippe Larroudé

Coastal long term processes, tidal characteristics and climate change

Hartmut Hein

Coastal flooding risks at the city of Oostende

Niels Balens

Parameterization of storm surges as a basis for assessment of risks of failure for

coastal protection measures

Dörte Salecker

Integrated risk analysis for extreme storm surges (XtremRisK)

Andreas Kortenhaus

Implementing coastal defence strategies for sandy coasts - reinforcement of

the Norderney dune revetment

Frank Thorenz

20:00 Social dinner (KHG)


Book of Abstracts - Conference Program V

th

Wednesday 8 June 2011

Technical Session 4 Coastal and Port Environments

Chairman: Dr. Gerald Müller

09:00

10:30

10:45

11:00

11:30

11:45

12:00

12:15

12:30

12:45

LECTURE 4: Modeling nearshore sediment transport processes

Bradley Johnson

Physical modelling of brine discharges from a cliff

Macarena Rodrigo

Monitoring of psammitic nearshore bedforms, their evolution and role as benthic habitat

Ulrich Floth

COFFEE BREAK

Efficiency of artificial sandbanks in the mouth of the Elbe estuary for damping the incoming

tidal energy

Janina Marx

Estimation of wave attenuation over a Posidonia oceanica meadow

Theoharris Koftis

The effect of organism traits and tidal currents on wave attenuation by submerged

vegetation

Maike Paul

Dynamic analysis of gravity quay walls under seismic forces

Kubilay Chian

(Architectural) measures to control wave overtopping inside harbours

Koen Van Doorslaer

LUNCH BREAK

14:15 Technical visit

th

Thursday 9 June 2011

Technical Session 5 Coastal Developments

Chairman: Dr.-Ing. Andreas Kortenhaus

09:00 LECTURE 5: Mathematical modelling of coastal sediment transport and beach evolution

Magnus Larson

10:30 Coastal protection of lowlands: are alternative strategies a match to

effects of climate change?

Hanz D. Niemeyer

10:45 The integrated coastal observation and model system COSYNA

Kai Wirtz

11:00 COFFEE BREAK

11:30 Shoreline detection in gentle slope Mediterranean beach

Carlo Lo Re

11:45 Re-examining the Dean profile for designing artificial beaches in Dubai

Andrew Brown


VI 5th International Short Conference on Applied Coastal Research - SCACR 2011

th

Thursday 9 June 2011

Technical Session 5 Coastal Developments

Chairman: Dr.-Ing. Andreas Kortenhaus

12:00

12:15

12:30

12:45

13:00

14:15

14:30

14:45

15:00

15:15

15:30

Further developments in a new formulation of wave transmission

Giuseppe Roberto Tomasicchio

A numerical study for the stability analysis of articulated concrete mattress

for submarine pipeline protection

Maria Gabriella Gaeta

Geosynthetic tubes as construction element for coastal protection works

– fundamental design aspects; application possibilities and practical experience

Markus Wilke

Wave overtopping resistance of grassed slopes in Viet Nam

Le Hai Trung

LUNCH BREAK

Technical Session 6 Modeling, Management

Chairman: Prof. Holger Schüttrumpf

Methods to detect changepoints in water level time series – application to the German Bight

Sönke Dangendorf

The coastDat data set and its potential for coastal and offshore applications

Elke M. I. Meyer

Wave impact on a seawall with a deck and on a baffle in front of seawall

Nor Aida Zuraimi Md Noar

Mapping the temporal and spatial distribution of experimental impact induced

pressures at vertical seawalls: a novel method

Gerald Müller

First results of large scale model tests on the stability of interlocked placed block revetments

Fabian Gier

Mooring lines and module connector forces measurements with different

anchoring typologies. Application to Aguete Port

Javier Ferreras

15:45 Discussion & Closing

The conference is sponsored by:


Book of Abstracts – Table of Contents VII

Table of Contents

Technical Session 1 – Coastal Structures

Kaan Koca, Senol Dundar, Sevket Cokgor, Baris Ozen and Özgür Durmuş

Modelling of turbulence fields in front of the rubble mound breakwater ................ 1

Gerald Morgan and Jun Zang

Simulating porous breakwaters with OpenFOAM – a sensitivity analysis ............. 3

Peyman Aghtouman, Fatemeh Aliyari and Zeinab Aghtouman

Effect of berm width on reshaped profile of berm breakwaters ............................... 5

Anja Brüning, Hans Fabricius Hansen, Flemming Schlütter and Ulrich Vierfuß

A hybrid modeling approach on floating breakwater dimensioning ....................... 7

Antonino Viviano, Carlo Lo Re, Luca Cavallaro and Enrico Foti

Run-up over variable slope bottom. Validation for a fully nonlinear Boussinesqtype

of model ................................................................................................................ 9

Antje Bornschein, Reinhard Pohl, Stefanie Lorke and Holger Schüttrumpf

Wave run-up on dikes ................................................................................................ 11

Guiseppe Barbaro, Giandomenico Foti and Giovanni Malara

A probabilistic approach for run-up estimation ...................................................... 13

Hiroaki Kashima and Katsuy Hirayama

Effects of surf beat caused by long period swell on wave overtopping rate on

complex bathymetry ................................................................................................... 15

Corrado Altomare, Leonardi Damiani and Xavier Gironella

Overtopping formula for vertical tiers-headed wall defences ................................ 17

Technical Session 2 – Coastal Processes

Luminita-Elena Boblea and Michael Hartnett

A development of an esturine hydrodynamic model in cylindrical coordinates .. 19


VIII 5th International Conference on Applied Coastal Research – SCACR 2011

Maria de Fátima Alves de Matos and Venerando Eustáquio Amaro

Characterization of hydrodynamics of a coastal lake system, Amapa, Brazil ...... 21

Peter Mewis

A 2D morphodynamic-numerical model of the surf zone “Strand” ...................... 23

Frank Kösters, Andreas Plüß, Marko Kastens and Harro Heyer

Long-term morphodynamic modeling of the German Bight – model set-up and

validation ..................................................................................................................... 25

Erik Horstmann, Martijn Siemerink, Marjolein Dohmen-Janssen, Tjeerd Bouma and Suzanne Hulscher

Sediment dynamics in a mangrove creek catchment ............................................. 27

Paolo Blondeaux, Giovanna Vittori, Antonello Bruschi, Francesco Lalli and Valeria Pesarino

Steady streaming and sediment transport in the boundary layer at the bottom

of sea waves..... ........................................................................................................... 29

Nelson Guillermo Rangel-Buitrago, Giorgio Anfuso and Theoharis Plomaritis

One year evolution of two beach sectors at Cadiz littoral (SW Spain): storm

impacts, erosion processes and (no) recovery ....................................................... 31

Alejandro López-Ruiz, Miguel Ortega-Sánchez, Asunción Baquerizo and Miguel Á. Losada

Short-term simulation of the evolution of a curvilinear coast ................................ 33

Technical Session 3 – Coastal Risk / Risk Management

Giovanna Vittori and Paolo Blondeaux

Turbulent boundary layer under a solitary wave: a RANS model .......................... 35

Vincent Gruwez, Annelies Bolle, Toon Verwaest and Hassan Wael

Numerical and physical modelling of wave penetration in Oostende harbour

during severe storm conditions ................................................................................ 37

Philippe Larroudé, Déborah Idier and Olivier Brivois

Numerical simulation for indicator of vulnerability to climate change on four

French beaches... ....................................................................................................... 39

Hartmut Hein, Stephan Mai and Ulrich Barjenbruch

Coastal long term processes, tidal characteristics and climate change...... ........ 41

Niels Balens, Xavier Valls, Johan Reyns, Toon Verwaest and Stefaan Gysens

Coastal flooding risk at the city of Oostende .......................................................... 43


Book of Abstracts – Table of Contents IX

Dörte Salecker, Angelika Gruhn, Christian Schlamkow and Peter Fröhle

Parameterization of storm surges as a basis for assessment of risks of

failure for coastal protection measures ................................................................... 45

Hocine Oumeraci, Jürgen Jensen, Gabriele Gönnert, Andreas Kortenhaus, Andreas Burzel,

Marie Naulin, Dilani Dassanayake, Thomas Wahl, Christoph Mudersbach, Kristina Sossidi and Gehad

Ujeyl

Integrated risk analysis for extreme storm surges (XtremRisK) ........................... 47

Frank Thorenz and Holger Blum

Implementing coastal defence strategies for sandy coasts – reinforcement

of the Norderney dune revetment ............................................................................. 49

Technical Session 4 – Coastal and Port Environments

Macarena Rodrigo, Francisco Vila, Antonio Ruiz-Mateo, Ana Álvarez, Ana Lloret and Manuel Antequera

Physical modelling of brine discharges from a cliff ................................................ 51

Ulrich Floth

Monitoring of psammitic nearshore bedforms, their evolution and role

as benthic habitat ....................................................................................................... 53

Janina Marx, Dagmar Much, Jens Kappenberg and Nino Ohle

Efficiency of artificial sandbanks in the mouth of the Elbe estuary for

damping the incoming tidal energy .......................................................................... 55

Theoharris Koftis and Panayotis Prinos

Estimation of wave attenuation over a Posidonia oceanica meadow ................... 57

Maike Paul and Tjeerd Bouma

The effect of organism traits and tidal currents on wave attenuation by

submerged vegetation ............................................................................................... 59

Kubilay Cihan, Yalçın Yüksel and Seda Cora

Dynamic analysis of gravity quay walls under seismic forces .............................. 61

Koen Van Doorslaer, Julien De Rouck and Stefaan Gysens

(Architectural) measures to control wave overtopping inside harbours .............. 63


X 5th International Conference on Applied Coastal Research – SCACR 2011

Technical Session 5 – Coastal Developments

Hanz D. Niemeyer

Coastal protection of lowlands: are alternative strategies a match to

effects of climate change? ......................................................................................... 65

Kai Wirtz and Friedhelm Schroeder

The integrated coastal observation and model system COSYNA ......................... 67

Giorgio Manno, Carlo Lo Re and Giuseppe Ciraolo

Shoreline detection in gentle slope Mediterranean beach ..................................... 69

Andrew Brown and Jon Kemp

Re-examining the Dean profile for designing artificial beaches in Dubai ............. 71

Giuseppe Roberto Tomasicchio, Felice D’Alesssandro and Gianluca Tundo

Further developments in a new formulation of wave transmission ...................... 73

Maria Gabriella Gaeta and Alberto Lamberti

A numerical study for the stability analysis of articulated concrete

mattress for submarine pipeline protection ............................................................. 75

Markus Wilke and Hartmut Hangen

Geosynthetic tubes as construction element for coastal protection works –

fundamental design aspects; application possibilities and practical

experience ................................................................................................................... 77

Le Hai Trung, Henk Jan Verhagen and Jentsje van der Meer

Wave overtopping resistance of grassed slopes in Viet Nam ................................ 79

Technical Session 6 – Modelling, Management

Sönke Dangendorf and Jürgen Jensen

Methods to detect changepoints in water level time series – application

to the German Bight ................................................................................................... 81

Elke M. I. Meyer, Ralf Weisse, Heinz Günther, Ulrich Callies, Hans von Storch, Frauke Feser,

Katja Woth and Iris Grabemann

The coastDat data set and its potential for coastal and offshore applications .... 83

Nor Aida Zuraimi Md Noar and Martin Greenhow

Wave impact on a seawall with a deck and on a baffle in front of seawall ........... 85


Book of Abstracts – Table of Contents XI

Dimitris Stagonas, Gerald Mϋller, William Batten and Davide Magagna

Mapping the temporal and spatial distribution of experimental

impact induced pressures at vertical seawalls: a novel method ........................... 87

Fabian Gier, Holger Schüttrumpf, Jens Mönnich and Matthias Kudella

First results of large scale model tests on the stability of interlocked

placed block revetments ............................................................................................ 89

Javier Ferreras, Antía López, Enrique Peña, Félix Sánchez-Tembleque and Andrea Louro

Mooring lines and module connector forces measurements with

different anchoring typologies. Application to Aguete Port ................................... 91

Poster Presentations

Hany Ahmed and Andreas Schlenkhoff

Investigation of the effect of permeability on wave interaction with a

barrier by application of PIV ...................................................................................... 93

Corrado Altomare and Girolamo Mauro Gentile

Monitoring phases of the re-naturalization process of the Torre del Porto

beach ........................................................................................................................... 95

Susumu Araki, Saki Fujii and Ichiro Deguchi

Numerical simulation on the motion of cubic armour block .................................. 97

Elvira Armenio, Felice D’Alessandro, Francesco Aristodemo and G. Roberto Tomasicchio

Estimation and verification of long-shore sediment transport at Lecce

coastline ...................................................................................................................... 99

Arne Arns, Hilmar von Eynatten, Roger Häußling, Dirk van Riesen, Holger Schüttrumpf and Jürgen Jensen

Developing sustainable coastal protection- and management strategies for

Schleswig-Holstein’s Halligen considering climate changes (ZukunftHallig) .... 101

Marcus Behrendt

Artificial surfing reefs – an option for the German Baltic Sea coast? ................. 103

Duccio Bertoni, Giovanni Sarti, Giuliano Benelli and Alessandro Pozzebon

Abrasion rates of marked pebbles on two coarse-clastic beaches at

Marina di Pisa, Italy .................................................................................................. 105

Holger Blum, Frank Thorenz and Hans-Jörg Lambrecht

Risk assessment for North Sea coastal lowlands in Germany ............................ 107

Stanley J. Boc Jr.

Innovative shore protection for communities ........................................................ 109


XII 5th International Conference on Applied Coastal Research – SCACR 2011

Sandro Carniel, Mauro Sclavo and Renata Archetti

The use of integrated wave-current-sediment numerical tools to model

coastal dynamics: applications in the North Adriatic Sea .................................... 111

Carla Faraci, Enrico Foti and Rosaria E. Musumeci

Estimate of cross-shore coastal erosion induced by extreme waves and

effects of sea level rise through ETS model .......................................................... 113

Christian Grimm, Daniel Bachmann and Holger Schüttrumpf

Risk management in coastal engineering – a case study in northern

Germany .................................................................................................................... 115

Angelika Gruhn, Peter Fröhle, Christian Schlamkow and Dörte Salecker

On the failure mechanism and failure probability of flood protection dunes

at the German Baltic Sea coast ............................................................................... 117

Stefanie Lorke, Sarah Horsten, Antje Bornschein, Reinhard Pohl, Holger Schüttrumpf and

Jentsje W. van der Meer

Wave and current interaction – Comparison of physical model tests with

numerical simulations .............................................................................................. 119

Bahare Majdi, Freydoon Vafai, S. Mohammad Hossein Jazayeri Shoushtari and Alireza Kebriaee

Opportunities and threats along Iranian coastlines .............................................. 121

Christos Makris, Constantine Memos and Yannis Krestenitis

Modelling of surf zone turbulence and undertow with the SPH numerical

method ....................................................................................................................... 123

Samir Medhioub, Abir Baklouti and Chokri Yaich

Impact of the dredging process on the granulometry of a shelly sand.

Case study of TAPARURA project, Sfax, Tunisia .................................................. 125

Lydia Nagler, Giuseppe Roberto Tomasicchio, Iván Cáceres, Felice D’Alessandro, C. Juana E. M. Fortes,

Michael James, Suzana Ilic, Agustín Sanchez-Arcilla, Francisco Sancho and Holger Schüttrumpf

Effect of wave overtopping on dune overwash and dune breaching .................. 127

Diogo R. C. B. Neves, L. Endres, C. Juana E. M. Fortes, T. Okamoto

Physical modelling of wave propagation and wave breaking in a wave channel129

Paulo Raposeiro, Maria Teresa Reis, Conceição Juana Fortes, João Alfredo Santos, Adriana Vieira,

Diogo Neves, Eduardo Brito de Azevedo, Anabela Simões and José Carlos Ferreira

Methodology for overtopping risk evaluation in port areas. Application

to the Port of Praia da Vitória (Azores, Portugal) .................................................. 131

Renata Archetti, Sandro Carniel, Claudia Romagnoli and Mauro Sclavo

Rapid evolution of shoreline after a beach nourishment downdrift of a

groin and at an embayed beach: theory vs. observation ..................................... 133


Book of Abstracts – Table of Contents XIII

Andrea Ricca, Felice D’Alessandro and Giuseppe Roberto Tomasicchio

Calibration and validation of an analytical model to predict dune erosion

due to wave impact and overwash .......................................................................... 135

Holger Schüttrumpf

Analysis of uncertainties in coastal structure design based on expert

judgement .................................................................................................................. 137

Ryszard Staroszczyk, Maciej Paprota and Wojciech Sulisz

Solitary wave impact on a seawall .......................................................................... 139

F. Sterlini, S. IJzer and S.J.M.H. Hulscher

Seasonal changing sand waves and the effect of surface waves ....................... 141

Pietro Danilo Tomaselli, Carlo Lo Re and Giovanni Battista Ferreri

Analysis of tide measurements in a Sicilian harbour ........................................... 143

Valentina Vannucchi and Lorenzo Cappietti

Estimation of wave energy potential of the northern Mediterranean Sea ........... 145

Adriana S. Vieira, Conceição Juana Fortes and Geraldo de Freitas Maciel

Comparative analysis of wind generated waves on the Ilha Solteira lake,

by using numerical models OndisaCad and Swan ................................................ 147


Book of Abstracts - Session 1: Coastal Structures 1

Modelling of turbulence fields in front of the rubble mound

breakwater

Kaan Koca 1 , Senol Dundar 2 , Sevket Cokgor 3 , Baris Ozen 4 and Özgür Durmuş 5

1 ABSTRACT

In order to design a coastal structure properly, wave–structure interactions should be taken into

account because wave motions are altered due to the obstruction to the flow path caused by

structures, thus a complex three-dimensional flow pattern is generated in their vicinity. During

this process turbulence is occurred and sediment transport characteristics of the flow are

changed due to the flow separation. This is particularly true for a porous coastal structure

(Losada et al., 1995). During the last decades, because of the complexity of turbulence

characteristics many laboratory studies have been performed in order to identify the process

involved near the structures in breaking and non-breaking wave conditions, have been reported

by many researchers (Stive, 1980; Stive and Wind, 1982; Nadaoka and Kondoh, 1982; Hattori

and Aono, 1985; Mizuguchi, 1986; Nadaoka et al., 1989; Ting and Kirby, 1994, 1995, 1996;

Sakakiyama and Liu, 2001; Losada et al., 1995). The enhanced turbulence have significant

impacts on wave forces thus on the scouring process at the toe of a structure as well as on

other mixing processes. Detailed velocity measurements are required to understand the

physical processes involved. Therefore, mathematical/numerical models that are to be used for

designing of the coastal structure can be validated (Sakakiyama and Liu, 2001). Rubble-mound

breakwaters are well known coastal structures, which constructed for different purposes all

around the world for ages. Knowing the turbulence characteristics in front of and within these

structures is important in terms of functionality and stability of the structures because the

structures are subject to wave forces thus additional shear stress on the armoring blocks of the

breakwater are generated.

In this paper, turbulent flow characteristics in front of a rubble-mound breakwater without

overtopping was studied and discussed. Magnitudes such as turbulence intensity, turbulence

kinetic energy (TKE), and turbulence shear stresses were calculated in front of the structure.

Experiments were carried out in a laboratory flume which has a length of 26 m, a width of 6 m,

and a height of 1.4 m. Regular waves were generated with a palette of flap type. The bottom of

the flume was inclined in the offshore direction of the breakwater with a slope value of 1/25. Still

water depth, d, was kept as constant with a value of 0.40 m at the front of the breakwater. The

breakwater surface was covered by two layers of crushed stones having a mean height, D, of

5.3 cm and a standard deviation of 0.85 cm; an impermeable layer was underlying these

crushed stones placed with a slope of 1/2.5. The crest of the breakwater (crown wall’s top level)

was 25 cm higher than the water level. Two scenarios were investigated. In the first scenario,

the breakwater was placed perpendicularly to the direction of incoming wave. In the second

scenario, the breakwater was placed in an 30 0 angle to the direction of incoming wave. Two

kinds of measurements were undertaken during the experiments: wave measurements by using

a resistant type wave probe and velocity measurements by using a 16 MHz NORTEK Acoustic

Doppler anemometer (ADV-VECTRINO). Measurements focused on the determination of wave

characteristics (e.g., wave height, period) were conducted at three different points in front of the

breakwater. These latter points were at a distance of 1 m, 2 m, and 5 m, respectively, to the

1 Istanbul Technical University, Hydraulics Laboratory, 34469, Istanbul, Turkey, kkaan.koca@gmail.com

2 Istanbul Technical University, Hydraulics Laboratory, 34489, Istanbul, Turkey, s.dundar@iku.edu.tr

3 Istanbul Technical University, Hydraulics Laboratory, 34469, Istanbul, Turkey, cokgor@itu.edu.tr

4 Istanbul Technical University, Hydraulics Laboratory, 34469, Istanbul, Turkey, ozenb@itu.edu.tr

5 Istanbul Technical University, Hydraulics Laboratory, 34489, Istanbul, Turkey, durmusoz@itu.edu.tr


eakwater. Velocity measurements were achieved at 40 points near the breakwater for 2

different wave conditions (breaking and non-breaking).

The time varying velocity data obtained during the above mentioned experiments then were

analyzed by decomposing the instantaneous velocity values into time-averaged mean values

and fluctuation components. Three methods were used to separate the turbulent components of

the velocity and were compared: numerical filtering scheme, Fast Fourier Transform (FFT) and

smoothing algorithm.

The first scenario, breakwater was placed parallel to the incoming wave, was conducted

successfully (Cokgor et al., 2011) and some of the results were given herein. Once the fluctuating

components were determined, turbulence intensity maps were plotted in order to investigate the

turbulence flow distribution in front of the breakwater.

z(m)

2 5th International Short Conference on Applied Coastal Research - SCACR 2011

Breakwater

u’rms(m/s)

Breakwater

x(m) x(m)

Figure 1: u’rms-w’rms map (horizontal and vertical components of the velocity)

As can be seen in Figure 1, u’rms map shows that above z/d=0.60 the horizontal component of

the turbulence intensity(u’rms) was stronger than that for the open sea. This can mainly be due

to the wave breaking near the surface. In this region, one must draw attention to the fluctuation

component of the velocity. The turbulence intensity was observed to have its largest value near

the breakwater surface; a remarkable amount of turbulence was created in and transported

from the armor layer. Below z/d=0.60, no significant turbulence was observed. w’rms map

shows virtually the same values for the vertical component of the turbulence intensity (w’rms).

However, the extension of the turbulence intensity observed in the vertical component is slightly

lower than that observed for the horizontal component in the region above z/d=0.60.

Consequently, turbulence intensities (u‘,w‘) were observed to take larger values in a region from

0.60d to still water level due to the contraction of waves.

The knowledge of the shear stress and the kinetic energy distribution is an important factor for

the stability of the structure. Such maps provide the necessary information on the potential

vulnerability of different zones around the structure.

z(m)

Breakwater

x(m)

Figure 2: Turbulence shear stress map in front of the structure

w’rms(m/s)

Figure 2 shows that the turbulence shear stress observed at toe of the breakwater is relatively

significant; this is thought to be a consequence of the local scouring at this lower zone. Between

z/d=0.375 and 0.75, the turbulence shear stress was observed to increase considerably and to

took its maximum value near the crest of the structure as expected. Turbulence shear stress

was observed to take larger values over the surface of the rubble-mound breakwater.


Book of Abstracts - Session 1: Coastal Structures 3

Simulating porous breakwaters with OpenFOAM – a sensitivity

analysis

Gerald Morgan 1 , and Jun Zang 2

1 Introduction

As computers increase in power and efficiency, complex computational techniques such as

CFD are becoming more and more practical as tools in engineering design. One engineering

discipline which has seen particular use of computational modelling is coastal and offshore

engineering. An often-used technique in the design of coastal structures is the use of porous

fills, breakwaters and armour layers to dissipate wave energy. These types of structures are

more complex to simulate using CFD, but the approach that is generally used is to modify the

Navier-Stokes equations to include additional momentum losses within the porous structure

based on the Darcy-Forchheimer equation.

The CFD model used in this research is OpenFOAM: a free, open-source library for the solution

of continuum-mechanics problems on unstructured finite-volume meshes. Porous media is

simulated by introducing n as a factor on the temporal term of the momentum equation and

adding two additional momentum sink terms: a Darcy term, Du and a Forchheimer term Fu|u|.

The parameters D and F in these momentum sinks can be directly related to the more

commonly used α and β parameters.

This sensitivity analysis is designed to study the effects of errors in the estimation of these n, α

and β parameters that control the porosity of a breakwater. There is significant scope for error in

these parameters. In an engineering design situation it is highly unlikely that the permeability, α

and the Forchheimer parameter of a fill will be precisely known, and the porosity may only be a

relatively crude estimate. Formulae exist for estimating α and β from the porosity and the

representative particle size, d50 (Sidiropoulou et al. 2007), but different formulae may give

answers that vary by orders of magnitude. Even in the laboratory situation there is room for

doubt as to whether a value of α calculated by conventional means is applicable to the highly

transient problem of wave transmission.

1 Analysis

The test case used in this paper is based on an experiment conducted at the University of

Aalborg and reported on by Troch (2000). Regular waves were generated in a rectangular wave

flume and interacted with the vertical front face of a surface-piercing, porous breakwater. Wave

gauges were used to record the run-up on the face of the breakwater, the wave reflection and

the wave transmission. In addition, an array of pore pressure sensors within the breakwater

recorded how the wave decayed as it passed through the breakwater. A fast, simple, CFD

model was constructed of this experimental test case. The calculation of the model was

automated in such a way that the model could be easily run for a large variety of porosity

parameters. A schematic of the test layout as used in this modelling is shown in figure 1.

This analysis considers eight porosities, covering the range from n = 0.1 to 0.9, eight

permeabilities with D ranging from 1 × 10 6 to 4 × 10 7 and five values of the Forchheimer

parameter, F, ranging from 0.02 to 2.0. Some example results showing wave decay within the

breakwater are shown in figure 2.

1 Dept. of Architecture and Civil Engineering, University of Bath, Claverton Down, Bath. g.c.j.morgan@bath.ac.uk

2 Dept. of Architecture and Civil Engineering, University of Bath, Claverton Down, Bath. j.zang@bath.ac.uk


4 5th International Short Conference on Applied Coastal Research - SCACR 2011

Figure 1: Schematic diagram showing the geometry and pressure gauge layout.

Figure 2: Results from the models showing the change in wave decay through the breakwater as

the permeability varies. For the breakwaters shown here, n = 0.1 and F = 0.2.

2 Conclusions

By comparing the results of these simulations the effect of the porosity parameters on the

modelled wave transmission and reflection of a porous obstacle can be deduced. From this, an

assessment can be made of the extent to which errors in estimation of the porous properties of

a material propagate to errors in the modelling of its wave transmission and reflection

performance.

It has been found that the OpenFOAM CFD model is capable of adequately reproducing

appropriate transient pore pressures within the breakwater for a wide range of incoming waves,

breakwater parameters and grid sizes. Even at the relatively coarse grid sizes and fast runtimes

required for a sensitivity analysis of this size, the results from the model have been

consistent with the published experimental data.

3 Acknowledgements

This research, undertaken at the University of Bath, has been funded by the University of Bath,

Great Western Research and Edenvale Young Associates Ltd. whose support is gratefully

acknowledged.

4 References

Troch, P. (2000): Experimentele studie ennumerieke modellering van golfinteractie met

stortsteengolfbrekers. PhD Thesis, University of Ghent.

Sidiropoulou, M. G.; Moutsopoulos, K. N. and Tsihrintzis, V. A. (2007): Determination of

Forchheimer equation coefficients a and b. In: Hydrological Processes, Vol 21, pp.534-

554


Book of Abstracts - Session 1: Coastal Structures 5

Effect of berm width on reshaped profile of berm breakwaters

Peyman Aghtouman 1 , Fatemeh Aliyari 2 , Zeinab Aghtouman 3

1 Abstract

Berm breakwater is a rubble mound structure and contains a wide range of armour stones. This

kind of structures will reshape under wave attack and final stable profile is main design criterion.

Apart from determining weight and grading of armour stones, a designer shall design the

geometry of the structure including berm width.

This research is an experimental study on the effect of berm width on reshaped profile of a

berm breakwater. This enables us to find out an optimum width to obtain better performance.

An important non-dimensional parameter named damage level was presented by Broderick

1984 which considers the amount of erosion area divided by nominal diameter of armour

stones. Van der Meer 1988, presented the non-dimensional parameters Ho and HoTo in order

to describe type of reshaping structures. Another important parameter to describe the amount of

reshaping is recession length especially in berm breakwaters. Kao and Hall 1990, Torum et al

2003 and Moghim et al 2009 have been presented some experimental results to predict

recession lengths.

Previous researches performed by Aghtouman. P. et al 2005 on armour layer thickness of

simple slope reshaping breakwaters was the main Idea for finding out the berm width effect on

reshaped profiles.

The physical modelling tests have been carried out in the wave flume of SCWMRI (Soil

Conservation And Watershed Management Research Institute). It’s equipped with a vertical

piston-type paddle and related irregular wave generation system Made by DHI. In this study

irregular waves with JONSWAP spectrum were generated. Plan view of the wave flume, model

and wave gages locations are presented in Figure 1.

Figure 1: Wave flume plan and setup of wave height meters

Based on mass conservation low as a main assumption, the previous simple slope reshaping

breakwater section has been chanded to a berm breakwater. An upper part (U) of the armour

layer has been cutted and then added to the down part (D). Therefore a berm breakwater

section has been made by a geometric change of the previous simple slope reshaping

breakwater. Figure 2, illustrates the berm breakwater model section in comparison with previous

simple slope reshaping breakwater section and the design assumptions.

1 SCWMRI, Shafie st., Asheri st., Karaj Special Road, Tehran, P.O Box 13445-1136 I.R.Iran, payman_7@yahoo.com

2 EIED(Energy Industries Engineering and Design), No.4, Second Koohestan st., Passdaran Ave., Nobonyad sq.,

Tehran 1958843811 I.R.Iran, aliyari-f@eied.com

3 Darya Negar Pars (DNP) Consulting Engineers, No. 41, 1st Towhid, Khovardin Blvd., Shahrake Gharb, Tehran, Postal

code: 1466994853, zeinab.aghtouman@yahoo.com


6 5th International Short Conference on Applied Coastal Research - SCACR 2011

Figure 2: Section of Berm breakwater model in comparison with previous simple slope section

For investigating the effect of berm width on reshaped profile, Four different relative berm

widths, B/Dn50 = 17.6, 20.6, 23.6 and 26.6 were employed. On the other hand, four relative wave

heights of H/Dn=4.0, 5.1, 6.2 and 6.3 were tested for the abovementioned widths. In order to

investigate on wave parameters effect on reshaping profiles, three different wave lengths with a

constant water depth have been considered. Constant relative water depth of d/Dn=14.1 and

three relative wave depths of d/Lop=0.095, 0.051 and 0.039 are considered.

2 Conclusion

Reshaped profiles with same hydrodynamic condition and different berm widths are compare

and presented in Figure 3 In order to find out the effect of berm width on reshaping profiles.

Z (cm)

60

40

20

0

Constants:

H/Dn=4.0

d/Dn=14.1

d/Lop=0.039

Water Level

Core

Filter layer

Main design profile B/Dn=26.6

Main design profile B/Dn=23.6

Main design profile B/Dn=20.6

Main design profile B/Dn=17.6

Reshaped profile B/Dn=26.6

Reshaped profile B/Dn=23.6

Reshaped profile B/Dn=20.6

Reshaped profile B/Dn=17.6

15 35 55 75 95 115 135 155 175 195

X (cm)

Z (cm)

60

40

20

0

Constants:

H/Dn=6.2

d/Dn=14.1

d/Lop=0.095

Water Level

Core

Filter layer

Main design profile B/Dn=26.6

Main design profile B/Dn=23.6

Main design profile B/Dn=20.6

Main design profile B/Dn=17.6

Reshaped profile B/Dn=26.6

Reshaped profile B/Dn=23.6

Reshaped profile B/Dn=20.6

Reshaped profile B/Dn=17.6

15 35 55 75 95 115 135 155 175 195

X (cm)

Z (cm)

60

40

20

0

40

20

0

Constants:

H/Dn=5.1

d/Dn=14.1

d/Lop=0.095

Water Level

Core

Filter layer

Main design profile B/Dn=26.6

Main design profile B/Dn=23.6

Main design profile B/Dn=20.6

Main design profile B/Dn=17.6

Reshaped profile B/Dn=26.6

Reshaped profile B/Dn=23.6

Reshaped profile B/Dn=20.6

Reshaped profile B/Dn=17.6

15 35 55 75 95 115 135 155 175 195

X (cm)

Z (cm)

60

Constants:

H/Dn=6.3

d/Dn=14.1

d/Lop=0.058

Water Level

Core

Filter layer

Main design profile B/Dn=26.6

Main design profile B/Dn=23.6

Main design profile B/Dn=20.6

Main design profile B/Dn=17.6

Reshaped profile B/Dn=26.6

Reshaped profile B/Dn=23.6

Reshaped profile B/Dn=20.6

Reshaped profile B/Dn=17.6

15 35 55 75 95 115 135 155 175 195

X (cm)

Figure 3: comparison of the reshaped profiles for different berm widths;

(H/Dn=4, d/Lop=0.039 up-left; H/Dn=5.1, d/Lop=0.095 up-right;

H/Dn=6.2, d/Lop=0.095 down-left; H/Dn=5.1, d/Lop=0.058 down-right)

3 References

Broderick (1984), L.L.: “RipRap Stability Versus monochromatic and irregular waves”, M.

Thesis, George Washington University, USA

Van der Meer, J.W. (1988): Rock slopes and gravel beaches under wave attack: Doctoral

Thesis, Delft University of Technology, Also: Delft Hydraulics Communication No. 396

Kao, J. S. and Hall, K. R., (1990): Trends in stability of dynamically stable breakwaters. ASCE.

Proc. 22nd ICCE, Delft, the Netherlands, Ch. 129

Tørum, A., Kuhnen, F., Menze, A., (2003): On berm breakwaters. Stability, scour, overtopping,

Coastal Engineering 49, pp. 209-238

Aghtouman, P., Chegini, V., Shirian N., Hejazi M., (2005): Design of reshaping breakwater's

Armour layer thickness, 2nd International Symposium in Iceland

Moghim M.N., Shafieefar M., Chegini V., Aghtouman P. (2009): Effects of irregular wave

parameters on berm recession of reshaping berm breakwaters: Journal of Marine

Engineering, Vol. 5, No. 9, pp. 35-51; ISSN 0733-950X


Book of Abstracts - Session 1: Coastal Structures 7

A hybrid modeling approach on floating breakwater

dimensioning

Anja Brüning 1 , Hans Fabricius Hansen 2 , Flemming Schlütter 3 and Ulrich Vierfuß 4

1 Motivation:

To fulfil the current requirements for a safe and unimpeded operation of the pilot ships at

Brunsbüttel different alternatives were checked. One of the options is a new pier for pilot ships

at the northern bank of the Elbe River close to the Kiel-Canal (NOK). Due to the large water

depths and a desire to minimise influence on the sediment transport, a floating breakwater was

chosen as a possible wave protection system for the new pier.

BAW, who is commissioned by the local water- and shipping administry (WSA Hamburg) for the

conceptual planning, requested DHI to undertake numerical simulations and physical model

tests in order to estimate the required dimensions and associated wave attenuation of the

floating breakwater.

Design conditions at this particular location would result in significant wave heights up to 1.7 m

during storm events with winds from WSW and wind speeds of 25 m/s. Ship wake induced

regular waves were considered as well. Here only the secondary ship waves can be considered

as primary waves are too long to be absorbed by the breakwater. The maximum acceptable

significant wave height at the pier is Hm0,max=0.95 m. The allowable maximum wave height is

about 1.8 m at the new pilot pier assuming the wave height obey a Rayleigh distribution.

This requires a protective structure that is able to reflect some of the incoming wave energy in

order to reduce the waves at the moored pilot ships to the acceptable level. Numerical models

were used to estimate wave reflection and transmission for different layouts and wave

conditions. Subsequently the most suitable dimensions of the floating breakwater were

determined.

Figure 1: First layout of floating breakwater and pier from the conceptual planning

(WSA Hamburg)

1 DHI-WASY GmbH, Branch Office Syke, Max-Planck-Str. 6,28857 Syke, Germany, abu@dhigroup.com

2 DHI, Agern Allé 5, 2970 Hørsholm, Denmark, hfh@dhigroup.com

3 DHI, Agern Allé 5, 2970 Hørsholm, Denmark, fls@dhigroup.com

4 Federal Waterways Engineering and Research Institute (BAW), Dienststelle Hamburg, Wedeler Landstrasse 157,

22559 Hamburg, Germany, Ulrich.Vierfuss@BAW.de


8 5th International Short Conference on Applied Coastal Research - SCACR 2011

2 Methods & Results:

As specific challenge, the initial conditions can be accentuated: The water depths are large and

wave periods are relatively long. Oblique wave attack restricts the damping effect.

Knowledge of the dimensioning and construction of floating breakwaters is available (see

PIANC 1994), but rarely for oblique wave attack and long wave periods.

In cooperation with BAW, DHI chose a hybrid approach to determine a suitable solution by

undertaking the following tasks:

1. The applicable design conditions were predefined by BAW. The wave spectra were

modelled for the area of interest in frequency and direction domain using MIKE 21

wave modelling technology.

2. From a starting layout a suitable floating structure was found by using the

diffraction/radiation code WAMIT® to analyze the response in waves of the floating

structures.

3. After identifying the layout and dimensions of the floating breakwater physical

model tests in DHI laboratories were used to verify the effectiveness of the floating

breakwater. Additionally movements of the pontoons and forces on the structure

were determined.

4. With the help of reflection and transmission properties and the forces found using

the physical model tests, the WAMIT®-model was calibrated.

Figure 2: WAMIT® - Result of one simulation (left) and corresponding test with the physical

model (right)

The following conclusions could be drawn from the study:

1. In spite of all optimizations the dimensions of the floating breakwater would result

large and uneconomic for the given initial conditions and requirements. So the

exposed position of the harbour was discarded.

2. The accuracy of the numerical modelling approach was successfully verified by

physical model tests.

3 References

PIANC. Report of Working Group no. 13 - PTC II - Supplement to Bulletin N° 85 (1994) Floating

Breakwaters – A practical guide for design and construction.

DHI (2009a) “MIKE 21 SW: Spectral Waves FM Module, Scientific Documentation”, Horsholm,

Denmark.

DHI (2009b) “MIKE 21 SW: Spectral Wave Module, User Guide”, Horsholm, Denmark.

WAMIT User Manual. Available from www.wamit.com


Book of Abstracts - Session 1: Coastal Structures 9

Run-up over variable slope bottom. Validation for a fully

nonlinear Boussinesq-type of model

Antonino Viviano 1 , Carlo Lo Re 2 , Luca Cavallaro 3 and Enrico Foti 4

1 Overview

The interaction of waves with the coast produces a great number of effects which influence at a

large extent the human activities near the sea. The main problems are caused by the erosion of

beaches and the inundation of the land behind the coastline. As a matter of facts, these two

effects are correlated; indeed the beach represents the first line of defence against extreme

waves, therefore the erosion enhances coastal flooding with more and more frequencies also

due to the climate changes. For such a reason, the eroded coasts are usually object of coastal

protection works, i.e. construction of structures, and/or of sand nourishment. In both cases the

cross-shore profile of the coast is strongly modified and typically presents several ranges with

variable slopes which make the studies of run-up and overtopping and, in turn, the coastal risk

mapping difficult to be performed.

Several authors have studied the run-up and overtopping of coastal structures and beaches.

Pullen et al. (2007), for example, collected a wide series of experiments and provided several

formulae for the maximum run-up covering also the case of variable sloping bottom. The same

authors have also inserted all their experimental data in a neural network code which can be

used for the cases falling out the limit of applicability of the formulae. However, the use of such

a formulation represents an empirical approach to the problem and it is not correlated to the

physical phenomenon of the wave approaching a slope.

In this framework, the present contribution aims at validating the physically based Boussinesqtype

of model of Lo Re et al. (2008) for the variable slope bottom case. Moreover, experimental

results are also shown which refer to a physical model configured in order to analyze the wave

run-up over variable bottom slopes, typical of several real cases.

2 Description of the numerical model

The adopted one horizontal dimension Boussinesq-type of model (Lo Re et al., 2008)

represents an extension of the model developed by Musumeci at al. (2005) in order to provide a

more physically based swash zone boundary condition and a fairly correct estimation of wave

run-up. More in details, the dynamics of the wave propagation within the surf zone is

represented through a weakly dispersive fully nonlinear Boussinesq-type of model. The flow is

assumed rotational after breaking and the governing equations are derived with no assumptions

on the order of magnitude of the nonlinear effects. Moreover, in such a model the velocity is

influenced by the effects of vorticity due to breaking, and the vorticity transport equation is

solved analytically under the assumption of depth constant eddy viscosity. The amount of

vorticity introduced by the breaking process is determined through the adoption of the concept

of the surface roller and by means of an analogy with the hydraulic jump. The shoreline

boundary condition is developed with a fixed grid method solving the shoreline equations

(Prasad and Svendsen, 2003). A linear extrapolation (Lynett et al. 2002) near the wet-dry

boundary has been also used in order to improve the stability of the numerical scheme.

1 Department of Civil and Environmental Engineering, University of Catania, Viale Doria 6, 95125 Catania, Italy,

nino.viviano@gmail.com.

2 Department of Hydraulic Engineering and Environmental. Application, University of Palermo,Viale delle scienze ed.8,

90128 Palermo, Italy, lore@idra.unipa.it.

3 Department of Civil Engineering, University of Messina, Contrada di Dio, 98166 Messina, Italy,

lcavallaro@ingegneria.unime.it

4 Department of Civil and Environmental Engineering, University of Catania, Viale Doria 6, 95125 Catania, Italy,

efoti@dica.unict.it.


10 5th International Short Conference on Applied Coastal Research - SCACR 2011

3 Description of the experimental set-up and synthesis of results

Some experiments on sloping beaches have been carried out from some authors of the present

contribution. Here the main results have been applied for the validation of the above mentioned

model. In particular, the experimental investigation has been conducted in the laboratory at

University of Catania showed in Figure 1. In such a Figure the bottom profiles are also shown.

In particular, each bottom profile is made up by three slopes: the first and the last slopes have

angle of 10° and 2° respectively, the middle one has an angle equal to 30° with respect to the

horizontal plane.

The experiments have been conducted with monochromatic waves. The acquisition of wave

heights has been conducted by a resistive probe place in a region located out of the initial

slope. The analysis of the wave run-up has been carried out by a digital camera which allowed

25 frames per second to be recorded. Each registered image has been calibrated in order to

obtain the real dimensions of the phenomenon to be registered. The water depth at the wave

gage has been ranged between 22 and 25 cm, the wave period has been varied between 0.67

to 0.91 s and the wave heights are in the range between 2.5 and 7.7 cm.

The Run-up measured has been related to the wave height and the water depth, moreover it

has been compared to the results obtained by the adopted numerical model in the same

condition, obtaining a fairly good match.

Figure 1: Picture of the wave flume at University of Catania with indication of the experimental

set-up, i.e. maximum bottom slope angle equals to 30 degrees.

4 Acknowledgements

This work has been partly founded by the Project PRIN 2008, titled: “Operative instruments for

the estimate of coastal vulnerability in the presence of sandy beaches also in the presence of

coastal structures”, founded by the Italian Ministry of education, University and Research.

5 References

Lo Re, C., Musumeci, R.E., Foti, E. (2008): A new shoreline boundary condition for a highly non

linear 1DH Boussinesq model for breaking waves, in Proceedings of the 3rd SCACR –

International Short Conference on applied coastal Research, pp. 211-218. ISBN 978-88-

6093-058-3. Lecce, Italy.

Lynett, P., Wu T.-R., Liu, P. L.-F. (2002). Modeling wave runup with depth-integrated equations.

In: Coastal Engineering, Vol 46, pp. 89–107.

Musumeci, R.E., Svendsen, I.A., Veeramony J. (2005): The flowin the surf zone: a fully

nonlinear boussinesq-type of approach. In: Coastal Engineering, Vol 52, pp. 565–598.

Prasad R.S and Svendsen I.A., Moving shoreline boundary condition for nearshore models.

Coastal Engineering, 49: 239–261, 2003.

Pullen, T., Allsop, N.W.H, Bruce, T., Kortenhaus, A., Schüttrumpf, H., van der Meer, J.W.

(2007): Eurotop. Wave Overtopping of Sea Defences and Related Structures:

Assessment Manual. www.overtopping-manual.com. ISBN 978-3-8042-1064-6.

10°


Book of Abstracts - Session 1: Coastal Structures 11

Wave run-up on dikes

Antje Bornschein 1 , Reinhard Pohl 1 , Stefanie Lorke 2 and Holger Schüttrumpf 2

The freeboard design of levees and dams is important for the safety of the structures itself as

well as the land protected by dikes. The Guideline 246/1997 of the German Association for

Water, Wastewater and Waste (DWA) is widely used in freeboard design in Germany. The

paper deals with the background of the guideline, experiences from the application and

discusses new aspects which came up recently during the analysis of run-up tests with oblique

wave attack under the influence of current and wind.

1 Design procedure

Data required for freeboard calculation are hydrological data (like design water level in a river,

at a sea coast or in a reservoir as a result of a flood event), meteorological data (wind velocity,

duration and direction) and structure related data (e.g. slope of the construction surface

upstream or on the sea side). The computation routine includes the estimation of the height of

incident waves and wind set-up, run-up calculation and the determination of freeboard height

regarding additional safety aspects.

The calculation routine of the German Freeboard Design Guideline was established considering

still water bodies like lakes or reservoirs. It has to be discussed if it is appropriate to use it for

rivers with wide floodplains or estuary dikes with considerable dike parallel currents.

2 New model tests

To clarify the influence of currents two model test series were conducted at the laboratory of the

Danish Hydraulic Institute in Hørsholm, Denmark in January and November in 2009. Figure 1

gives an overview of the model set-up.

(1)

Figure 1: Model set-up in DHI laboratory in Denmark with wave maker (1), wind generator (2),

wave gauges (3), run-up gauge (4) and overtopping measurement units (5).

The measurements included both overtopping and wave run-up. The considered dike had a

smooth surface with a waterward slope of 1:3 and 1:6 respectively. Wave generator made

different long-crested waves using a JONSWAP spectrum.

1 Technische Universität Dresden, Institut für Wasserbau und Technische Hydromechanik, 01062 Dresden, Germany.

antje.bornschein@tu-dresden.de

(2)

2 Institute of Hydraulic Engineering and Water Resources Management, RWTH Aachen, Kreuzherrenstraße 7, 52056

Aachen, Germany, scacr@iww.rwth-aachen.de

(3)

dike‐parallel

current

(4)

(5)

(5)


12 5th International Short Conference on Applied Coastal Research - SCACR 2011

Wind, a current parallel to the dike crest and different angels of wave attack were considered

within the model test series to investigate the constraints of wave run-up. The model set-up was

presented in Lorke et al. (2010).

3 Run-up test results

Run-up measurement equipment includes a capacitive gauge on a run-up plate and film

recording using digital camera with following analysis. This enables to measure the maximum

run-up as well as the mean run-up height.

Results were analysed regarding the influence of current, wind and oblique wave attack as well

as combined effects of these influencing parameters. Existing formulas were verified (e.g.

EurOtop-Manual 2007) and new dependencies are tried to be taken into account. Lorke et al.

(2010) has presented first results.

Figure 2: Factor � � versus angle of wave attack � and angle of wave energy � e, test results and

empirical functions (1:3 sloped dike)

To quantify the influence of oblique wave attack as well as current a reduction factor was

calculated on basis of test results. Some results are summarized in Figure 2. The results of

model tests without currents verify existing empirical functions. The combined analysis of

oblique wave attack and currents seams to cause a stronger reduction effect (yellow line).

4 Acknowledgements

The project is founded by German Ministry of Education and Research (BMBF) and the Coastal

Engineering Board of Trustees (KFKI). The model-tests in Hørsholm, Denmark were cofinanced

under the HYDRALAB III program of the European Union. The authors wish to express

their thanks for the financial support.

5 References

DVWK (1997): Freibordbemessung von Stauanlagen. DVWK-Merkblatt 246/1997

EurOtop-Manual (2007): European Overtopping Manaual. www.overtopping.manual.com

Lorke, S., Brüning, A., van der Meer, J., Schüttrumpf, H., Bornschein, A., Gilli, S., Pohl, R.,

Spano, M., Riha, J., Werk, S., Schlütter, F. (2010): On the Effect of Current on Wave

Run-up and Wave Overtopping, in: Proceedings of the 32nd International Conference

on Coastal Engineering, Shanghai, China.


Book of Abstracts - Session 1: Coastal Structures 13

A probabilistic approach for run-up estimation

Giuseppe Barbaro 1 , Giandomenico Foti 2 and Giovanni Malara 3

1 Abstract

The run-up is the highest level where the water arrives on the beach during a storm. This

parameter is essential for the design of any coastal structure. It is a random variable related to

the significant wave height of the sea states which occur during a storm. In this paper, the runup

is estimated by a probabilistic approach. Specifically, the return period of a storm in which

run-up exceeds a fixed threshold is estimated. It is determined from the equation

R

�RX� u2%


� � ��

��

�1

N

R

i

1

�H�h; � � ��

2 � � � � � ��

2�

s

i

i

� �



�1

, (1)

where N is the number of sectors in which wave directions have been divided, Ru2% is the 2%

exceedence value of run-up, R(Hs>h;θi-∆θ/2


14 5th International Short Conference on Applied Coastal Research - SCACR 2011

Eq. (3) and eq. (4) are irrespective of the dominant direction, but they yield a conservative

estimate of the return period (1).

Eq. (1) and eq. (2) are applied in conjunction with the empirical expression proposed by

Stockdon et al. (2006) for run-up estimation. That is,


1

1 �

R

� � L

2%

p0

� 2 �

� �

� � �

1 L

u

p0

2

2

� K � 1. 1 0.

35�

f � �

� � �0. 563�

f � 0.

004���,

(5)

h

� � h � 2 ��

h

��




where Lp0 is the dominant wave length at deep waters, h is the significant wave height at deep

waters and βf is the beach slope. Specifically, the significant wave height related to a fixed runup

threshold X is determined as h=X/K. Then, the return period (2) is calculated and used in eq.

(1).

A practical situation is considered. The return period (1) is estimated at Alghero (Italy) and at

Kauai Island (Hawaii, USA). Starting from buoy data given by the ISPRA (Istituto Superiore per

la Protezione e la Ricerca Ambientale) and NDBC (National Data Buoy Center), the results of

the calculation are discussed. Figure 1 shows the return period (1) at Alghero and at Kauai

Island. It is shown that, for example, by assuming a return period R(Ru2%>X) = 10 years, the

value of Ru2%, at Alghero, is 2.4m, and, at Kauai Island, Ru2% is 2 m. The ETS model allows

estimating the mean persistence of Ru2% above a fixed threshold X, as well. For the aforementioned

example, it is shown that the mean persistence above 2.4 m is 6.5 hours, at Alghero.

The mean persistence above 2 m at Kauai Island is 3.4 hours.

100000

10000

1000

100

10

1

R(R u2%>X) [yr]

X [m]

0.1

0 1 2 3 4 5

100000

10000

1000

100

10

1

R(R u2%>X) [yr]

X [m]

0.1

0 1 2 3 4 5

Figure 1: Return period (1) at the location of Alghero (left panel) and at Kauai Island (right panel).

2 References

Arena, F.; Barbaro, G. (1999): Il rischio ondoso nei mari italiani (in Italian). Ed. Bios Cosenza,

Italy. ISBN 88-7740-276-8.

Boccotti, P. (2000): Wave Mechanics for Ocean Engineering. Elsevier Science, Oxford. ISBN 0-

444-50380-3.

Stockdon, H. F., Holman, R. A., Howd, P. A., Sallenger, A. H. Jr. (2006): Empirical

parameterization of setup, swash, and runup. In: Coastal Engineering, Vol. 53, No. 7,

pp. 573-588; ISSN 0378-3839.


Book of Abstracts - Session 1: Coastal Structures 15

Effects of surf beat caused by long period swell on wave

overtopping rate on complex bathymetry

Hiroaki Kashima 1 and Katsuya Hirayama 2

1 Introduction

Recently, coastal disasters due to long period swell induced by heavy storms increase in the

Japanese coasts and harbors. Authors conducted the calculations on the wave transformation

of long period swell at Shimoniikawa coast with complex bathymetry, Toyama Prefecture

(Kashima and Hirayama, 2009). It was found that the long period swell is more susceptible to

the bottom topography of offshore deeper water and its wave height locally increases by the

wave energy concentration due to the refraction and wave shoaling in the relatively shallower

water. In addition, the wave overtopping rate may become larger by sea level increasing due to

surf beat with wave groupings. Therefore, an accurate estimation of wave transformation on

long period swell is important to understand the characteristics of wave overtopping rate on

seawall. Kashima and Hirayama (2010) conducted the experiments to measure wave

overtopping rate of long period swell on one dimensional seawall and Tajima et al. (2009)

analyzed the spatial propagation characteristics of long period swell by numerical simulations.

However, the spatial relationship between wave overtopping rate and surf beat caused by long

period swell are still unknown due to the lack of detail model experiments and the difficulty of

numerical simulations.

The purpose of this study is to make clear the spatial characteristics of wave overtopping rate

for long period swell on the complex bathymetry, experimentally. First, the spatial

measurements of wave fields and wave overtopping rate around the damaged seawalls are

carried out in the large basin generating the long period swell estimated by observed data.

Second, the spatial relationships between wave overtopping rate and surf beat caused by long

period swell will be discussed based on the experimental data set, the filtered profiles, their

statistics and the spectra of surface elevation and two dimensional horizontal velocities.

2 Outline of experiments

The experiments were conducted in the wave basin that is 48.0 m and 25.0 m long and 1.5 m

deep located in Port and Airport Research Institute in Japan. A detail of the experimental setup

is shown in Fig.1 where y is the horizontal coordinate from the ridge line (y = 0km), x is the

horizontal coordinate from the wave maker. A complex bathymetry was installed and offshore

water depth was 90.0 m in the actual field. The irregular wave trains were generated by PC

controlled 100 wave paddles with active wave absorber. The experimental scale was 1/100 in

Froude similarity rule. The water suface elevation, water velocities and wave overtopping

volume were measured to understand the wave fields and spatial characteristics of wave

overtopping rate on seawalls. The incident wave condition was estimated with the observed

data at the wave observation station near the damaged area, which was H1/3 = 5.97 cm and T1/3

= 1.39 s in offshore with 0.9 m deep and whose principal wave direction was 15.0 degrees

equivalent to N18.5W degrees and frequency spectral profile was equivalent to JONSWAP

spectra with � = 4.0.

3 Results and discussions

The significant wave height of short-wave less than 30s increases by the wave energy

concentration on the ridge and decreases in front of the seawalls under the effects on the wave

breaking due to coastal structures (Fig.1a). On the other hand, the surf beat height becomes

1 Port and Airport Research Institute, 3-1-1 Nagase, Yokosuka , Kanagawa, 239-0826, Japan, kashima@pari.go.jp

2 Port and Airport Research Institute, 3-1-1 Nagase, Yokosuka , Kanagawa, 239-0826, Japan, hirayama@pari.go.jp


16 5th International Short Conference on Applied Coastal Research - SCACR 2011

** * * * * *

(m)

** * * * * *

(a) short-wave height (b) surf beat height

Figure 1: spatial distributions of significant wave height of short-wave less than 30s and surf beat

(lines: depth contour, o: measurement points of wave height, *: measurement points of

wave overtopping volume)

Figure 2: relationship between wave overtopping and wave statistics in front of the damaged

seawalls (upper figure; significant wave height of short-wave (solid line) and surf beat

height (dashed line), lower figure; dimensionless wave overtopping rate)

larger in the relatively shallower water, in paticular behind the coastal structures on the sharply

slope (Fig.1b). Fig.2 shows the spatial relationship between the wave overtopping rate and the

short or long wave height. The total wave overtopping rate in the experiments is 7.8*10 -3 m 3 /m/s

and is in good agreement with the one estimated by the field investigation (6.1*10 -3 m 3 /m/s). In

the area with the steeper bottom slope (from y = -0.4 toward -0.7 km), the wave overtopping

rate tends to increase and its maximum value is appeared at y = -0.7 km where the surf beat

height is the largest although the short-wave height is relatively small. Moreover, the spatial

profile of the wave overtopping rate is in good agreement with the one of surf beat height. On

the other hand, the wave overtopping rate is relatively small although the short-wave height is

the largest. These imply that the effects of the surf beat caused by long period swell are

important for increase of the wave overtopping rate on the seawall.

The detail characteristics of the surf beat and generating mechanism of wave overtopping rate

will be presented at the conference.

4 References

Kashima, H and K. Hirayama (2009): Effects of bottom topography characteristics on

transformations of long period swell, in: Proceedings of the 4th SCACR – International

Short Conference on applied coastal Research, pp. 197-205. ISBN 978-3-00-030141-4.

Barcelona, Spain.

Kashima, H and K. Hirayama (2010): Experiments on wave overtopping rate and wave pressure

on seawalls of long period swell, Technical Note of The Port and Airport Research

Institute, No.1218, 26p (in Japanese).

Tajima, Y., H. Ishizashi and S. Satoh (2009): Concentration of slowly-varying nearshore waves

and currents around the edge of two different bottom slopes, Journal of JSCE, Ser. B2

(Coastal Engineering), Vol.65, pp.211-215 (in Japanese).

(m)


Book of Abstracts - Session 1: Coastal Structures 17

Overtopping formula for vertical tiers-headed wall defences

Corrado Altomare 1 , Leonardo Damiani 2 and Xavier Gironella 3

1 Introduction

Coastal structures are commonly built to protect coastal zones against storm surge and large

waves, that may cause overtopping flows over these structures, leading to damages of the

landward area, with hazards related to the security and human safety. Overtopping is a complex

and nonlinear wave phenomenon, random in time and volume, depending on geometrical,

structural and hydraulic parameters. It occurs because wave flows pass over the crest of a

structure. In reality there is no constant discharge, therefore a mean overtopping discharges is

measured because it is relatively easy.

2 Predicting wave overtopping

Different methods may be available to predict overtopping. Each method will have strengths or

weaknesses in different situations. The primary prediction methods are empirical ones using a

simplified representation of the phenomena of the process by means of physical modelling,

usually presented in the form of dimensionless equations, to relate the overtopping discharge to

the main hydraulic and geometrical parameters. A different approach is the use of the Neural

Network tool trained using the test results in the CLASH database. It is organised in the form of

layers of “neurons” connected each other. Each connectivity, as a result of the calibration, has a

weight factor assigned.

3 Model test cases

Experimental tests were conducted at LIM laboratory of UPC in order to assess the overtopping

mean discharge over the dike of a particular sea wall, tiers – headed, with freeboard of about

7.35 m. A submerged breakwater is located at a distance of 80 m seaward. The model was a

2D physical one, by means of the small flume facility, called CIEMito. The scale is 1:50 and

irregular wave trains with different wave steepness are tested. The surface profile and

significant wave features are measured using 8 resistive sensors. The overtopping discharge

was measured collecting wave volume in 3 tanks behind the structure. An analysis of the sea

wall without submerged breakwater was done in order to evaluate the influences of the last one

in term of dissipation and transmission of wave energy.

4 Analysis

The empirical formula of European Overtopping Manual and the NN were used to calculate as a

first approach the mean discharge for each test condition. The results have been compared with

measured discharges, pointing out huge differences as we expected, because of the particular

geometrical layout of the sea wall, hard to be represented in the prevision tools. To take into

account the effect of the stair-steps, an adjusting coefficient was introduced, related to wave

condition at the toe of the structure. Using a regression analysis the best accuracy in the results

was founded for a coefficient depending on square root of non - dimensional depth parameter

d*, as defined in EurOtop Manual. The correction founded was introduced into NN changing the

effective values of freeboard, differently from the geometrical one.

1 PhD, Laboratori d’Enginyeria Marítima (LIM), Universitat Politecnica de Catalunya (UPC), Jordi Girona, 1-3, Edif. D1,

Barcelona, 08034, Spain, corrado.altomare@upc.edu

2 Professor, Water Engineering and Chemistry Department (DIAC), Technical University of Bari, via E. Orabona, Bari,

70125, ITALY,l.damiani@poliba.it

3 Professor, Laboratori d’Enginyeria Marítima (LIM), Universitat Politecnica de Catalunya (UPC), Jordi Girona, 1-3, Edif.

D1, Barcelona, 08034, Spain, xavi.gironella@upc.edu


18 5th International Short Conference on Applied Coastal Research - SCACR 2011

5 Results and discussions

The application of a corrective coefficient to the EurOtop formulae and NN led to better

accuracy (fig.1) in term of calculated mean overtopping discharge compared with measured

values. In the following figure, for example, are shown the results obtained with the empirical

formulations.

q _ calculated (mc/s/m)

8,000E-05

7,000E-05

6,000E-05

5,000E-05

4,000E-05

3,000E-05

2,000E-05

1,000E-05

0,000E+00

0,000E+00 1,000E-05 2,000E-05 3,000E-05 4,000E-05 5,000E-05 6,000E-05 7,000E-05 8,000E-05

q _ measured (mc/s/m)

EurOtop formula

NN

EurOtop formula_corrected

NN_corrected

Figure 1: Mean overtopping discharge calculated compared with measured discharge

6 Conclusions

The European Overtopping formulae and Neural Network represent nowadays the best tools for

a forecasting analysis of overtopping, but it seems necessary going on with experimental tests

in order to adjust them to more complex geometrical and structure configuration of sea

structure. In particular, in the present work, a coefficient was found, related to parameter d*, to

take into account the effect of a tiers – shaped head for a vertical breakwater.

7 References

Pullen T. et al. (2007): EurOtop - Wave overtopping of sea defences and related structures:

assessment manual. Die Küste, www.overtopping-manual.com

Allsop W. et al. (2008): Improvements in wave overtopping analysis: the EurOtop overtopping

manual and calculation tool. Proc. COPEDEC VII, Dubai, UAE.

Pullen T. et al.(2008): EurOtop – overtopping and methods for assessing discharge. Flood Risk

Management: Research and Practice, Samuels et al. (eds.) ISBN 978-0-415-48507-4;

pp 555-560.


Book of Abstracts - Session 2: Coastal Processes 19

A development of an estuarine hydrodynamic model in

cylindrical coordinates

Luminita-Elena Boblea 1 and Michael Hartnett 2

1 Introduction

Estuaries and coastal areas have been the most populated regions around the world, with 60%

of the world’s population living in these regions. According to the US Bureau of the Census,

worldwide the human population is doubling every 30-50 years; due to migration, along many

coasts the population is doubling approximately every 20 years. Anthropogenic effects are

adverse to these important systems due to discharging non point and point sources of waste.

Although natural waters (rivers, lakes, oceans) have an ability of self-purification, impacts of

pollutants in these waters have shown that legislation protecting them against polluters,

improving or conserving their status has to exist. In Europe, Directives of the European Union,

e.g. Water Framework Directive, regulate the water quality legislative framework. Also, coastal

flooding due to tides, storm surges and waves needs to be mitigated against. Therefore,

development of efficient hydrodynamic, solute transport and water quality models is necessary

in order to help us better understand and forecast these complex phenomena.

Details of development of a new two-dimensional estuarine hydrodynamic model in cylindrical

polar coordinates are presented. The advantage of using this approach is that the coordinate

system can be fitted to estuary’s shape. This way a fine resolution is obtained in coastal area

and a coarse resolution away from the coast provided that position of the pole is appropriately

chosen. Moreover, the boundary error is reduced when compared to Cartesian coordinates. In

the end, the model is aiming at obtaining more accurate results without increasing

computational costs.

Section 2 describes mathematical modelling and methodology for obtaining the solution of the

governing equations in two-dimensions, preliminary results are given in section 3, whereas

section 4 presents conclusions of the present research.

2 Mathematical Modelling and Methodology

Water motion is described by the Navier-Stokes (NS) equations, which represent the basis of

hydrodynamic modelling. They describe the changes in flow. The shallow water equations result

from applying the specific properties of the estuary or coastal area to the momentum

conservation (NS) equations. For a given domain, hydrodynamic modelling also implies the

continuity principle, which states that mass and energy are constant. Due to the complexity of

the studied system, the analytical solution of the continuity and momentum equations could not

be obtained. Therefore numerical methods were employed.

The model simulated a 20km long harbour defined between two concentric circles (r1=7500m,

r2=27500m) and two radii (θ1=252º, θ2=288º) making a 36º angle at the centre (figure 1). A

constant water depth of 10.0m and a uniform bed were considered. For the defined harbour the

Navier-Stokes and continuity equations were written in cylindrical coordinates in terms of

instantaneous velocities and body force. Because the solution of the governing equations was

sought for shallow water estuarine and coastal areas, the three-dimensional Navier-Stokes and

continuity equations were depth integrated. For turbulence modelling the Boussinesq

assumption was employed. Subsequently, the depth integrated equations were mapped onto a

rectangular domain using analytical relationships. Tidal forcing was specified at the open

boundary of the domain (r2=27500m). Solution of the governing equations was obtained with a

conservative finite difference method using Thomas algorithm. The finite difference methods

1

National University of Ireland, College of Engineering and Informatics, l.boblea1@nuigalway.ie

2

National University of Ireland, College of Engineering and Informatics, michael.hartnett@nuigalway.ie


20 5th International Short Conference on Applied Coastal Research - SCACR 2011

present the advantages of being straightforward and easy to use unless the coefficients

involved in the equations are discontinuous. Therefore, the transformed momentum and

continuity equations were approximated using a finite difference scheme with an Arakawa C

grid.

Figure 1: Considered domain

3 Preliminary Results

Results obtained using both the new model and a rectangular model for the same geometry,

were as follows:

� Boundaries of the considered harbour were represented by interpolation onto a

rectangular grid for the rectangular model. Subsequently, a 58x50 grid was

employed with grid spacing ∆x=∆y=353m. Simulation time has been 50.00 hours,

and time step was ∆t=20.0sec. Tidal forcing was specified within rectangular model

on a straight line, due to the inability of specifying the forcing on a curved boundary.

� The new model was run for the same simulation time (50.00 hours), and

∆t=20.0sec. Computational grid dimensions were 41x37 with grid spacing ∆x=∆y=1.

Tidal forcing was specified with the same expression as within the rectangular

model.

� Both water elevations and total velocities predicted by the new model were greater

than those predicted by rectangular model. Also, a phase shift could be noticed in

the new model predicted water elevations.

� Due to the geometry considered, with a larger width at r2=27500m and narrowing

width until r1=7500m, a slight increase in water level was expected. Both models

predicted the increase, with new model results larger than those obtained from

rectangular model. Total velocities predicted by rectangular model at r=8000m were

greater than those predicted by the new model.

4 Conclusions

Development of a two-dimensional estuarine hydrodynamic model in cylindrical polar

coordinates was presented herein. Comparisons between the results obtained using both the

new model and a rectangular model for the same geometry show good agreement and further

research is considered for evaluation and verification of the new model.

5 References

Roy, G.D.; Humayun Kabir, A.B.M.; Mandal, M.M.; Haque, M.Z. (1999): Polar coordinates

shallow water storm surge model for the coast of Bangladesh. In: Dynamics of

Atmospheres and Oceans, Elsevier, Amsterdam, PAYS-BAS, INIST-CNRS, pp.397-413;

ISSN 0377-0265.

Morinishi, Y.; Vasilyev, O.V.; Ogi, T. (2004): Fully conservative finite difference scheme in

cylindrical coordinates for incompressible flow simulations. In: Journal of Computational

Physics, Vol.197, No. 2, pp.686-710, ISSN: 0021-9991.


Book of Abstracts - Session 2: Coastal Processes 21

Characterization of hydrodynamics of a coastal lake system,

Amapa, Brazil

Maria de Fátima Alves de Matos 1 , Venerando Eustáquio Amaro 1

1 Introduction

This paper presents a study on the coastal hydrodynamics processes operating system and a

fluvial-lacustrine, flood plains associated with river and estuarine tidal semidiurnal, located in the

coastal plain of the state of Amapá, 300 km long in the Region Coastal Brazilian Amazon

(Matos, 2009). The lake system is part of the Biological Reserve of Lake Piratuba, conservation

unit integral. The region represents an extremely dynamic industry where the morphological and

sedimentological occur in spatial and temporal scales. Most of these lakes are in the southern

coastal plain are composed of types of pelitic sediments deposited in the northern part of the

Amazon River to Cape Orange located in the northern state of Amapa. The region has been the

focus of many studies in various areas of knowledge, however, are still tentative, given the

difficulty of access to the area as a major constraint.

1.1 Study Area

The areas is bordered by three lakes of the coastal plain: Ventos Lake, Mutuco Lake and

Comprido de Baixo Lake. The area is located about 50 km of coastline, between geographic

coordinates: 1º24’6”N – 50º25’40”W and 1º18’”N – 50º’16’18”W, covers a drainage area of

36,270 km 2 (Figure 1).

Figure 1: Location of study area and points of measurements.

2 Methodology

Due to its importance and geoenvironmental socioeconomic, this work aims to characterize the

hydrodynamic processes in order to understand the context of geoenvironmental fluviallacustrine

system in action, based data acquisition of liquid discharge and current with use of

acoustic profiles (ADCP) and tides in May and October 2008, based on the methodology of

1 Federal University of Rio Grande do Norte, Campus University, Lagoa Nova, C.P. 1596, CEP: 59078-970, Natal, Rio

Grande do Norte, Brazil, mfatimaalves.m@gmail.com, amaro@geologia.ufrn.br


22 5th International Short Conference on Applied Coastal Research - SCACR 2011

Kosuth & Filizola (1998) and Silva & Kosuth (2001). This study also relation the morphodynamic

analysis by remote sensing in the period between 2005 and 2010.

3 Results and Dicussion

The results show in the region, especially the month of May (rainy month) is a period

characterized by high rates of water discharge, flow velocities and sediment transport; the

month of October, dry season, the hydrodynamic regime of the area is significantly reduced in

lower water rates (Figure 2), in effect, the system of lakes, large morphological features are

exposed. These results add to a body of research has been conducted in order to deepen our

knowledge of Amazonian lake environments , and support the development of the Management

Plan of the Biological Reserve of Lake Piratuba.

Liquid discharge (m³/s)

250

225

200

175

150

125

100

75

50

25

0

Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec

Discharge Tide Level Flow Speed Wind Speed

7,5

6,0

4,5

3,0

1,5

0,0

Wind (m/s)

3,0

2,2

1,5

0,7

0,0

Relative Level (m)

1,4

0,7

0,0

Figure 2: Relation between the mean discharge, flow speed, combined with tide levels and the

variation of local winds.

4 Acknowledgements

The authors thank CAPES, the network 05-PETROMAR/2007-

CTPETRO/FINEP/PETROBRAS/CNPq. In special, the authors thank the staffs of the

Geoprocessing Laboratory, Department of Geology (GeoPro UFRN) and the Center for Aquatic

Research (NUPAq/IEPA/Amapa).

5 References

Matos, M. F. A. (2009): Characterization of hydrodynamic and morphodynamic processes of the

lakes southern belt of Lake Piratuba Biological Reserve. Dissertation (Master of

Geodynamics) – Graduate Program in Geophysics and Geodynamics, Federal

University of Rio Grande do Norte, Natal, Rio Grande do Norte, Brazil. 142p.

Kosuth, P.; Filizola, N. P. (1998): Tidal effects on the evolution of the levels and discharge of the

Amazon River downstream of Óbidos 05 to 10/10/1998. Brasilia-DF, Brazil.

Silva, M. S.; Kosuth, P. (2001): Behavior of the liquid discharge of the river Matapi in

27/10/2000. In: 8 th Congress of the Brazilian Association for the Study of the

Quaternary, pp. 594-596, Imbé-RS, Brazil.

Velocity Magnitude (m/s)


Book of Abstracts - Session 2: Coastal Processes 23

A 2D morphodynamic-numerical model of the surf zone

“Strand”

Peter Mewis 1

1 Numerical model

“Strand” is a numerical model for morphodynamic simulation of the surf zone. It simulates

vertically integrated flow velocites and sediment fluxes on unstructured triangular meshes.

flow model

shallow water

equations

currents by

waves, wind

sediment

entrainment

sediment

concentr

wave

height

sediment transport by

- mean flow

- asymmetry (vertical

and horizontal)

- undertow

- downslope

transport

- mass transport

wave model

“SWAN”

wave

orbitals

bed changes

Figure 1: Flow chart of the computation in “Strand”

The sediment transport in the surf zone is a highly complicated process and still under research.

However basic properties of long-shore and cross-shore sediment transport are well recognized

and implemented in one-dimensional models. The combination of both directions is best

realized in a two-dimensional model, which accounts for the basic known processes. The flow

chart of “Strand” is given in figure 1, together with the modelled processes for the transport of

the sediment.

The effect of these processes depend on the particle size and on hydrodynamic parameters and

is implemented in a parametric form. In “Strand” a very simple implementation is used.

The advantages of such a model are:

� real two-dimensional model with most important structures resolved

� wave breaking and intense transport at bar systems in the foreshore, eventual

bypassing of sediment is present

� account for different partially counteracting processes

1

Institute of Hydraulic Engineering and Water Resources Research, TU-Darmstadt, Petersenstr. 13, 64387 Darmstadt,

mewis@wb.tu-darmstadt.de

bed

level


24 5th International Short Conference on Applied Coastal Research - SCACR 2011

The time is accelerated using the morphodynamic factor technique. This factor enables

simulations corresponding to a time span of several years. In this case the scenarios with their

forcing need to be selected carefully for the purpose of long term simulations, as described by

D. Roelvink earlier.

2 Application of Strand

The model has been applied to the tideless Baltic Sea Coast at different locations. The ability to

reproduce longshore bars has been demonstrated as well as the ability to simulate the beach

development behind a breakwater resulting in a salient or tombolo.

The application of the model is also possible for the simulation of morphodynamic changes

around jetties, breakwaters, artificial reefs, permeable and impermeable groines and in an

navigational channel. The model can also be applied for the optimization of beach nourishment

campaigns.

Figure 2: Computed depth changes in front of a marina for 290° wind and wave direction, red

color indicated accretion in front of the marina.

In Figure 2 the depth changes resulting from a 290° strong wind period are shown. In the

computation the typical accumulation east or “upstream” of the harbour jetties is retained.

During the simulation it is moving a bit seaward. The depth in front of the jetties decreases (dark

red color). At this location a pronounced accumulation of a more than 2.5 m takes place. Due to

the undertow the depth is not all the time very small close to the jetty. In a 10° wind direction

simulation this area in front of the jetties is deepening, because the sediment is moving seaward

forming a bar in that case not shown here.

In general the model is capable of reproducing a concave beach profile, which is similar to the

well known Bruun’s profile. This is a result of the counteraction of wave induced transport via

asymmetry and mass transport velocity and downslope transport.

Moreover the model is capable of reproducing a breaker bar, as indicated in figure 2. This is

achieved by the implementation of the undertow mechanism following the approach for the

breaker region of Svendsen. Because the bar is a strong sediment conveyor it’s dynamics is

very important for sediment balance and morphodynamic development.

3 References

Roelvink, J.A. and M.J.F. Stive. 1989. Bar-generating cross-shore flow mechanisms on a beach. Journal of

Geophysical Research, 94, 4785-4800.

Roelvink D. and J.-D. Walstra. 2004. Keeping it simple by using complex models. Proceedings of the 6 th

International Conference on Hydroscience and Engineering, Brisbane, Australia.

Mewis, P. 2006. Nearshore morphodynamic-numerical computation of the influence of harbour

jetties. Proceeding of the 30 th International Conference on Coastal Engineering 2006,

Vol. 4, 3835-3842.


Book of Abstracts - Session 2: Coastal Processes 25

Long-term morphodynamic modeling of the German Bight –

model set-up and validation

Frank Kösters 1 , Andreas Plüß 1 , Marko Kastens 1 and Harro Heyer 1

1 Introduction

Tidally driven sediment transport is an important factor for the morphological evolution of the

coastal zone. However, modeling of large-scale and long-term sediment dynamics in the past

was mostly restricted to 1d- and 2d-models (van Rijn, 2004). With increased computational

resources the AufMod-C project takes a process oriented modeling approach to further

investigate the large-scale, long-term morphodynamic evolution of the German Bight. Here we

present the validation of the hydrodynamic model as well as first morphodynamic results for the

initial sorting of sediments and the comparison for different meteorological situations.

2 Numerical model

The three-dimensional model is based on the numerical method UnTRIM (Casulli and Zanolli,

2002) using an unstructured, orthogonal grid in the horizontal to provide a good representation

of the complex coastal bathymetry and coastline. The model is based on a previous version of

Plüß (2004). Sediment transport and morphological evolution are calculated using SediMorph

(Malcherek, 2003) coupled to UnTRIM. The effects of waves are taken into account using a

discrete spectral wave model (Schneggenburger, 2000) applied on a triangular grid. The year

2006 was taken as reference year for calibration purposes using realistic forcing. Tidal

elevations were obtained from the global ocean tide model FES-2004 (Lyard et al., 2006) and

daily river-runoff for the German estuaries from observations. The wind field results from the

operational model of the “Deutscher Wetterdienst” (DWD). Salinity is relaxed to climatological

values at the boundaries; temperature is not taken into account. The initial sediment distribution

at the bottom is taken from a data based sediment model which has been developed within

another project of the AufMod framework.

3 Results and discussion

The North Sea model reproduces large-scale hydrodynamic features such as amphidromic

points realistically (see Fig. 1).

50

49

W4

W3

57

56

59

58

55

W3

W2

W1

60

54

W3

W2

W1 0 W1 0

53

52

51

E1

49

50

E1

E2

E3

E4

E5

E6

E7

E8

E9

E10

E11

E12

E3

51

E5

52

E7

E8

E9

55

54

53

60

59

58

57

56

Topographie (Watt)

mNN

-3. 0

3.

M_2-Gezeit (Amplitude)

m

0 1

2.

50

49

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W3

W3

W2

57

56

59

58

55

W1

60

W3

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W1 0 W1 0

50

E1

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E3

E4

E5

E6

E7

E8

E9

E10

E11

E12

Figure 1: Amplitude (left) and phase (right) of the M2 tide in the model domain.

E3

51

E5

52

E7

E8

E9

55

54

53

60

59

58

57

56

Topographie (Watt)

mNN

-3. 0 3.

M_2-Gezeit (Phase)

Grad

0 108.0 216.0

360.0

1 Federal Waterways Engineering and Research Institute, Wedeler Landstr. 157, 22559 Hamburg, Germany,

Frank.Koesters@baw.de


26 5th International Short Conference on Applied Coastal Research - SCACR 2011

In order to quantify the model skill the modeled water levels are compared with tide gauge data

at 84 locations covering the whole North Sea. Moreover, current velocities and wave

characteristics are compared to measured data within the German Bight. As the model

reproduces the observed hydrodynamic forcing well, it can be used to simulate sediment

transports. Starting from an average sediment distribution for the nine sediment fractions

considered here, the model evolves towards observed values, reproducing finer sediments at

the mudflats and coarser sediments in the tidal channels. When starting from the data based

model the time for this adjustment process can be significantly reduced yielding a realistic

sediment distribution (see Fig. 2).

Figure 2: Mean grain size after 3 months of model integration starting from observed values.

4 Acknowledgements

The AufMod-C project “Setting up integrated modeling systems for analyzing long-term

morphodynamics of the German Bight” (03KIS084) is part of the AufMod project funded by the

“Kuratorium für Forschung im Küsteningenieurwesen” (KFKI).

5 References

Casulli, V. and Zanolli, P. (2002): Semi-Implicit Numerical Modeling of Non-Hydrostatic Freesurface

Flows for Environmental Problems. Mathematical and Computer Modelling,

36:1131–1149

Lyard, F.; Lefevre, F.; Letellier, T. and Francis, O. (2006): Modeling the global ocean tides:

modern insights from FES2004 Ocean Dynamics, 53, 394-415

Malcherek, A.; Piechotta, F; Knoch D.(2003): Mathematical Module SediMorph – Standard

Validation Document Version 1.0, Technical Report, Bundesanstalt für Wasserbau.

Plüß, A. (2004): Das Nordseemodell der BAW zur Simulation der Tide in der Deutschen Bucht.

Die Küste 67, 83-127

Schneggenburger, Christoph, Günther, Heinz, and Rosenthal, Wolfgang (2000): Spectral wave

modelling with non-linear dissipation: validation and applications in a coastal tidal

environment. Coastal Engineering, 41, 201–235.

Van Rijn, L.C. (2004): Estuarine and Coastal Sedimentation Problems, Proceedings of the Ninth

International Symposium on River Sedimentation, Yichang, China


Book of Abstracts - Session 2: Coastal Processes 27

Sediment dynamics in a mangrove creek catchment

Erik Horstman 1,2 , Martijn Siemerink 1,2 , Marjolein Dohmen-Janssen 1 , Tjeerd Bouma 3,4 and

Suzanne Hulscher 1

1 The importance of mangrove development and aim of this study

Mangroves consist of trees and shrubs adapted to grow on water-logged soils in the intertidal

area of tropical and sub-tropical coasts. Mangroves provide a thriving habitat for many animals

and they provide mankind with an abundance of ecosystem services (e.g. wood and food). Next

to that the presence of mangrove vegetation in the intertidal zone impacts on coastal dynamics.

Hydrodynamic energy is being attenuated (Mazda et al. 1997) and sediments are being trapped

(Furukawa et al. 1997).

Sedimentation in mangroves is a very important feature from the perspectives of stabilization of

coasts and climate change impacts. Alongi (2008) found that field studies in mangroves

generally show average sedimentation rates that are slightly higher than the local rates of mean

sea level rise. However, field data on the flow paths of water and sediments through mangroves

is limited yet. Sediment dynamics in mangrove creeks have been studied in several field sites,

as well as sediment deposition in a mangrove catchment. However, the linkage between

sediment transport and deposition in mangroves and the input and output of sediment through

creeks and over the mangrove fringe (bordering the sea/river) is relatively unknown.

Currently we are performing a field campaign with the aim to determine how deposition in

mangroves occurs, in order to understand the importance of mangroves for coastal stabilization.

To that end we perform measurements to determine sediment deposition patterns, to monitor

sediment fluxes through the forest and to determine how the sediments enter the mangroves,

i.e. either over the mangrove fringe or through the creeks.

2 Field measurements

Our study site is a mangrove creek catchment in Trang province, Thailand (figure 1).

Figure 1: The field site is located at the Andaman coast in Thailand. From left to right: the Thai

Andaman coast; the coast of Trang province; the mangrove area around Kantang Tai

village; and an impression of the creek catchment under study (about 150x150 m2).

Within the creek catchment several processes are being monitored on a 24-points grid (see

figure 1). At these grid points we measure: 3D flow velocities (Acoustic Doppler Velocimeters),

water levels (pressure sensors), suspended sediment concentrations (water sampling) and

1 University of Twente, Water Engineering and Management, P.O. Box 217, 7500 AE Enschede, The Netherlands,

e.m.horstman@utwente.nl; m.siemerink@student.utwente.nl; c.m.dohmen-janssen@utwente.nl;

s.j.m.h.hulscher@utwente.nl

2 Singapore-Delft Water Alliance, National University of Singapore, 1 Engineering Drive 2, 117576 Singapore.

3

Netherlands Institute of Ecology, Centre for Estuarine and Marine Ecology, PO Box 140, 4400 AC Yerseke, The

Netherlands, t.bouma@nioo.knaw.nl

4 Deltares, Marine & Coastal Systems, PO Box 177, 2600 MH Delft, The Netherlands


28 5th International Short Conference on Applied Coastal Research - SCACR 2011

sediment deposition rates (sediment trapping). The topography of the entire creek catchment

has been mapped with laser altimetry (Total Station combined with GPS reference points) and

the vegetation within the area will be characterized by counting heights, densities and diameters

of all types of vegetation. These measurements will be executed continuously over a period of

four months, which is longer than most previous studies in mangroves, so to cover a range of

spring-neap tidal cycles and hopefully a storm event.

3 Expected results

Our first data indicate that inundation of mangroves during a tidal cycle shows two mechanisms:

creek flow and sheet flow. The creeks are being filled during flood tide until the creek banks

overflow and the forest starts to inundate. At overbank flow, flow velocities in the creek

accelerate, resulting in a large influx of water (and sediments) into the mangroves (figure 2).

Sheet flow is initiated over the mangrove fringe and is the second mechanism for water influx

into mangroves (figure 2). The relative importance of both mechanisms is of interest, because of

their impact on sediment fluxes (e.g. origin and direction). For salt marshes, the equivalent of

mangroves in temperate climates, Temmerman et al. (2005) found comparable results.

Figure 2: Horizontal flow velocities measured in a mangrove creek (left) and right in the

mangrove fringe (right) of our study site. Velocity measurements are executed with an

Acoustic Doppler Velocimeter and positive values indicate the landward direction.

Simultaneously with current velocities, suspended sediment concentrations are being sampled.

Together, these data will be used to compute sediment fluxes into and out of the creek

catchment; both through the creek (creek flow) and through the mangrove front (sheet flow).

Our final aim is to link sediment deposition patterns to these sediment fluxes through the forest

and to the sediment source being either the mangrove fringe or the creek.

4 Acknowledgement

This project is funded by the Singapore-Delft Water Alliance and Deltares.

5 References

Alongi, D.M. (2008): Mangrove forests: Resilience, protection from tsunamis, and responses to

global climate change. In: Estuarine Coastal and Shelf Science, Vol. 76, No. 1, pp. 1-13;

ISSN 0272-7714.

Furukawa, K.; Wolanski, E. and Mueller, H. (1997): Currents and sediment transport in

mangrove forests. In: Estuarine Coastal and Shelf Science, Vol. 44, No. 3, pp. 301-310;

ISSN 0272-7714.

Mazda, Y.; Wolanski, E.; King, B.; Sase, A.; Ohtsuka, D. and Magi, M. (1997): Drag force due to

vegetation in mangrove swamps. In: Mangroves and Salt Marshes, Vol. 1, No. 3, pp.

193-199; ISSN

Temmerman, S.; Bouma, T.J.; Govers, G.; Wang, Z.B.; De Vries, M.B. and Herman, P.M.J.

(2005): Impact of vegetation on flow routing and sedimentation patterns: Threedimensional

modeling for a tidal marsh. In: Journal of Geophysical Research-Earth

Surface, Vol. 110, No. F4, pp. 18; ISSN 0148-0227.


Book of Abstracts - Session 2: Coastal Processes 29

Steady streaming and sediment transport in the boundary layer

at the bottom of sea waves

Paolo Blondeaux 1 , Giovanna Vittori 1 , Antonello Bruschi 2 , Francesco Lalli 2 , Valeria Pesarino 2

1 The model

At the leading order of approximation in the wave steepness, the fluid motion induced by wave

propagation close to the bottom gives rise to a symmetric oscillatory flow and no net sediment

motion. However, at the second order of approximation, non-linear effects produce a steady

velocity component and a net sediment transport which become significant for waves of large

amplitude. Hence, to obtain reliable estimates of the sediment transport rate in coastal

environments and to predict erosion and deposition processes along with the appearance of

large scale morphological patterns, it is necessary to have a detailed knowledge of the flow

within the bottom boundary layer which is generated by propagating surface waves and, in

particular, to take into account nonlinear affects. A large number of works has been devoted to

determine the amount of sediments moved by propagating sea waves. An exhaustive review of

the results obtained is not the aim of the present contribution. Let us only point out that, quite

often, both the theoretical/numerical analyses and the laboratory experiments consider a

stream-wise uniform flow. For example, recently, Hassan & Ribberink (2010) have used a one

dimensional RANS diffusion model to study sand transport processes in an oscillatory boundary

layer and have verified the results of their model by comparing the theoretical predictions with

laboratory measurements performed in wave tunnels. Both the theoretical analysis and the

experimental measurements consider a stream-wise uniform flow while the actual flow at the

bottom of sea waves depends on the coordinate x* in the direction of wave propagation and this

spatial dependence induces phenomena, the most important of which is the generation of a

steady streaming, which cannot be observed in the uniform case. In particular, the sediment

transport is largely affected by the steady part of the velocity field. The objective of this

contribution is to present the results of a detailed analysis of the steady velocity and net

sediment transport in the fully-developed turbulent wave boundary layer, produced by a uniform

train of progressive finite-amplitude surface waves. Turbulence characteristics are determined

by means of a two-equation closure model of turbulence. In particular, the turbulence model

proposed by Saffman (1970) is employed. The model can describe both smooth and rough

bottoms as well as transitional regimes such that turbulence characteristics depend both on the

Reynolds number, the relative roughness size and the phase of the wave. Moreover the model

can describe the viscous sub-layer and allows the no-slip condition to be forced at the sea bed.

We estimate the sediment transport rate by evaluating the bed load by means of an empirical

predictor and the suspended load which is computed as the sediment flux, after the

determination of sediment concentration by the integration of an appropriate advection-diffusion

equation.

2 The results

To check the capability of the Saffman's model to predict the turbulent velocity field within the

oscillatory boundary layer generated by sea waves, when the flow regime is turbulent, the

computed velocity profiles and bottom shear stresses are compared with existing experimental

data. Such a comparison is also made to test the accuracy of the numerical approach and the

reliability of the computer code. Figure 1 shows a comparison between the bottom shear stress

computed by the model and that measured by Jensen et al. (1989) for test 10 and test 13. The

vanishing of the bottom shear stress around Φ=165 o and Φ=345 o for both the smooth and rough

wall cases is simulated quite well by the model and the overall agreement is satisfactory.

1

Department of Civil, Environmental and Architectural Engineering, University of Genoa, Via Montallegro 1, 16145

Genoa, Italy. blx@dicat.unige.it

2

Istituto Superiore per la Ricerca e la Protezione Ambientale - ISPRA. Via Curtatone 3, 00185 Rome, Italy


30 5th International Short Conference on Applied Coastal Research - SCACR 2011

Measurements of sediment concentration in the boundary layer generated close to the bottom

of a large oscillating water tunnel were carried out by Ribberink & Al-Salem (1994). Figure 2

shows a comparison between the model results and the measurements for T=6.5 s, R=0.655

and Urms=0.5 ms -1 . The agreement between the model predictions and the laboratory

measurements is more than acceptable where the concentration is significant and supports the

estimate of the sediment transport rate provided by the present model.

τ * /ρ * [(cm/s) 2 ]

70

60

50

40

30

20

10

0

-50 0 50 100

φ

150 200 250

τ * /ρ * [(cm/s) 2 ]

120

100

80

60

40

20

0

-50 0 50 100

φ

150 200 250

Figure 1: Dimensional wall shear stress versus wave phase for an oscillating flow over a) a

smooth wall and b) a rough wall. The solid curves are calculated profiles and the points

are the data from Jensen et al. (1989), test10 and test 13 respectively

y * [cm]

10

1

0.001 0.01 0.1 1 10 100

c [g/lt]

Figure 2: Suspended concentration profile in plane-bed and sheet flow conditions. The solid

curve is calculated profile and the points are the data of Ribberink & Al-Salem (1994),

test B7.

3 Acknowledgements

This study has been partially funded by the 'Ministero dell'Istruzione, dell'Università e della

Ricerca' under the research project 2008YNPNT9-003 'Idrodinamica e morfodinamica nella

regione dei frangenti'.

4 References

Jensen, B.L.; Sumer, B.M.; Fredsoe J. (1989) Turbulent oscillatory boundary layers at high

Reynolds numbers. In: J. Fluid Mech. 206, 265-297.

Ribberink, J.S.; Al-Salem, A.A. (1994) Sediment transport in oscillatory boundary layers in

cases of rippled beds and sheet flows. In: J. Geophys. Res. 99, (C6), 12707-12272.

Saffman, P.G. (1970) A model for inhomogeneous turbulent flow. In: Proc. Roy. Soc. London

A317, 417-433.


Book of Abstracts - Session 2: Coastal Processes 31

One year evolution of two beach sectors at Cadiz littoral (SW

Spain): storm impacts, erosion processes and (no) recovery

Nelson Guillermo Rangel-Buitrago 1 , Giorgio Anfuso 2 and Theoharis Plomaritis 3

The comprehension of morphological changes through time of a littoral system can be

characterised by means of a detailed field monitoring program and the analysis of

hydrodynamic conditions. In several, different littoral environments, storms suppose the main

factor of morphological changes with erosion and damages on littoral settings with associated

important economics losses and scores of deaths. During past decades, Cadiz littoral (SW

Spain) have undergone important erosion problems with locally recorded values greater than 1

myr -1 , essentially associated with storm events. In Cadiz area, storms constitute diffuse and

weak low Atlantic pressure systems that can continue for several days and affect large areas,

producing severe damages to coastal structures and erosion of beaches and dunes. In this

sense, there is a need to characterize storms and associated morphological coastline changes

in order to define, compare and predict their impacts. The main goal of this work is to

investigate the response of two closely located beach sectors during the past year in Cadiz

littoral using DGPS beach surveys and wave climate data. In detail, during the 2009-2010

period, very energetic conditions have been experienced with a total amount 16 storms events,

turning the investigated year in one of the most storminess one in the past half-century. The two

study sectors, both 500 m in length, are located at: i) Levante Beach, an ultradissipative, nourbanised

beach on the southern part of the El Puerto de Santa Maria Municipality and ii)

Camposoto Beach, a intermediate-reflective beach with medium level of occupation on the

western part of San Fernando Municipality. Levante and Camposoto beaches are located in two

littoral spits (Valderagrana and Camposoto spits, respectively) which consist of quartz rich sand

beaches, dune ridges (locally showing washover fans) and salt marshes. Both areas

correspond with mesotidal, semidiurnal environments characterised by dominant winds blowing

from ESE and NWN with significant wave heights values usually lower than 1 m. An amount of

thirteen 3D subaereal and intertidal beach surveys, extended from the dune foot to a water

depth of about one meter below low tide, have been carried out with a DGPS from December

2009 to December 2010. Beach volume and slope have been calculated along two transects in

each beach survey. For the climatic characterization and storm definition, wave data from

November 2009 to December 2010 have been obtained from the buoy REDCOS 1320

belonging to the Puertos del Estado Network, located at a depth of 21m, in front of Cadiz City.

The time series used contains more than 7,000 data collected with a frequency of 1 hour. The

storms have been defined according to the Dolan and Davis (1992) Storm Power Index which

allowed classifying storms in terms of the significant wave height (Hs) and duration in hours (td),

following the formulation Hs 2 td. Calculations have been carried out considering a threshold of

2.5 m because this value reflected the wave height at which erosion started to affect Cadiz

beaches according to ongoing studies. Taking into account the semidiurnal regime of the area,

the minimum storm duration has been fixed in 12 hours with an interstorm period of 24 hours.

Storm power index values have been categorized into five classes from weak, moderate,

significant, severe and extreme. In the investigated period, Levante and Camposoto beach

experienced 16 storms events which have been divided into 5 groups according to their

temporal distribution. The first group, from the 18 th December 2009 to the 14 th January 2010,

consisted of 7 events (2 weak, 3 moderate and 2 significant), summing a total of 14 gale days

1

Universidad de Cádiz, Facultad de Ciencias del Mar y Ambientales, Polígono Río San Pedro S/N 11510 Puerto Real

(Cádiz) Spain, nelson.rangelbuitrago@mail.uca.es

2

Universidad de Cádiz, Facultad de Ciencias del Mar y Ambientales, Polígono Río San Pedro S/N 11510 Puerto Real

(Cádiz) Spain, giorgio.anfuso@uca.es

3

Universidad de Cádiz, Facultad de Ciencias del Mar y Ambientales, Polígono Río San Pedro S/N 11510 Puerto Real

(Cádiz) Spain, haris.plomaritis@uca.es


32 5th International Short Conference on Applied Coastal Research - SCACR 2011

(344 hours). The second one, from the 15 th to the 29 th February, recorded 3 weak and 2

moderate storm events that impacted the zone for a period of 127 hours. The rest of the groups

corresponded with 1 weak storm of 29 hours on the 2 th April, 2 storms in October and 2 storms

between the 15 th November to the 10t h December 2010. The comparison of the beach profiles

surveyed during the investigated year, revealed different beach responses in according to the

number and intensity of storms. At Levante Beach winter storms produced dune lowering and

dune foot retreat of c. 25 m, and beach erosion in the backshore and accretion in lower

foreshore according to beach pivoting mechanism at mean sea level. As results, beach slope

decreased from 0.024 to 0.018, and 19.23 m 3 /m of sand have been eroded during the studied

year. At the same time, Camposoto beach experienced parallel retreat due to winter storm

impact which produced cross-shore sand movement during the spring and summer seasons,

and beach erosion in the backshore and accretion in lower foreshore during the autumn. During

the studied year, a total amount of 45.91 m 3 /m of sand have been lost in Camposoto beach. In

resume, main morphological changes at both sectors have been associated with the impact of

the first group of 7 storms occurred during the months of December 2009 and January 2010

which produced a beach pivoting at mean sea level at Levante Beach and parallel retreat at

Camposoto Beach. Small beach recovery took place along the whole foreshore in both beaches

during the spring and summer seasons. Finally, first autumnal storms produced a relatively

important loss of sediments, this way leaving both investigated beaches in a negative budget at

the beginning of the new incoming winter season.

1 References

Dolan R. and R.E., Davis, (1992). An intensity scale for Atlantic coast northeast storms. In:

Journal of Coastal Research, Vol. 8 Nº 4, pp. 352-364, ISSN 0749-0208.


Book of Abstracts - Session 2: Coastal Processes 33

Short-term simulation of the evolution of a curvilinear coast

Alejandro López-Ruiz 1 , Miguel Ortega-Sánchez 2 , Asunción Baquerizo 3 and Miguel Á. Losada 4

1 Introduction

Coastal zone management requires the proper modeling of morphological changes that occur

as a result of a complex multi-scale interaction between the climatic conditions and the

topography. It also requires to account for the intrinsic uncertainty associated to the stochastic

character of the climatic forcing (Baquerizo and Losada, 2008). This is particularly important at

littoral zones with a relevant environmental and socio-economic value, like the spits at the

mouth of estuaries.

López-Ruiz et al. (2011) have shown that the formation, growth and decay of shoreline

sandwaves at spits is strongly dependent not only on the wave climate severity and persistence

but also on the alternance of storms with mild conditions. They used in their work a one-line

model that incorporates a sediment transport formulation that accounts for the effect of wave

propagation at a conic-type bathymetry.

For changes occurring over decadal scales, Baquerizo and Losada (2008) presented a

methodology to predict the evolution of morphological features driven by climatological agents

and the assessment of the associated intrinsic uncertainty. In this work we use their

methodology with the model proposed by López-Ruiz et al. (2011) to analyse the uncertainty of

the evolution of the Doñana Spit at the Guadalquivir estuary (Spain).

2 Methodology

The procedure proposed by Baquerizo and Losada (2008) is based on the assumption that

morphologic changes in coastal areas are cumulative processes, so their response to a certain

state is the initial condition for the next sea state.

With the model of López-Ruiz et al. (2011) for the evaluation of the evolution of a certain stretch

of the coast to a sea state, it is possible to imitate the process during a certain period of time by

using as a forcing mechanism the local wave climate simulated as a series of consecutive sea

states. The model can be launched with the first sea state and the initial condition. The

cumulative forcing of the series of states during V years is then accounted for by subsequently

applying the evolution model with the prediction made with the previous state as an initial

condition. The resulting morphological situation after V years is considered as the final outcome

of an experiment. Finally, it is possible to apply probabilistic techniques to analyze the sample

space obtained with the outcomes of several repetitive numerical experiments.

2.1 One line model for the evolution of a curvilinear coast

Spits at river mouths show at their tips a curvilinear shoreline with a relatively small radius of

curvature. The sorrounding conic-type bathymetric contours produce a concentration of energy

and a variation of the alongshore wave energy (figure 1). Under these conditions the traditional

longshore sediment transport formulations are not directly applicable. To account for these

longitudinal variability, López-Ruiz et. al (2011) proposed to solve the mass conservation

equation in curvilinear coordinates using a sediment transport formula that integrates Inman and

Bagnold (1963) formulation along a section perpedicular to the shore.

1

Centro Andaluz de Medio Ambiente. Universidad de Granada. Avda. del Mediterráneo, s/n. 18006 Granada, Spain.

alopezruiz@ugr.es

2 miguelos@ugr.es

3 abaqueri@ugr.es

4 mlosada@ugr.es


34 5th International Short Conference on Applied Coastal Research - SCACR 2011

Figure 1: Left figure: wave energy concentration due to a conic-type bathymetry; Right figure:

Doñana sandy spit, at the mouth of Guadalquivir river (Spain).

3 Application to Doñana Spit (Spain)

Doñana sandy spit is located at the mouth of the Guadalquivir estuary, in the Gulf of Cádiz

(figure 1). This is a very important zone in terms of biodiversity and also from a socio-economic

perspective due to its proximity to the navigation channel of the fluvial harbor of Seville (Spain).

López-Ruiz et. al. (2011) analyzed its evolution under different climatic conditions and explained

the formation and growth of observed shoreline sand waves for relatively energetic conditions

and their decay under persistent mild conditions. Figure 2 shows an initially unperturbed

shoreline and its position after a sequence of 5 storms. The figure also shows the breaker line

position. It can be observed that the surfzone width varies alongshore due to wave energy

concentration at the tip of the spit. This variation induces the formation of shoreline sand waves

with length scales λ ≈1500 m and amplitudes a≈150 m.

Figure 2: Evolution of the shoreline position after a storm with a significant wave height

Hs=3.5 m, mean zero-upcrossing period Tz=12 s, and wave progagation direction

θ=55º.

In the final paper, a predictive analysis of the shoreline position after a few years of climatic

forcing will be presented. It will include also an assesment of the uncertainty of the presence or

absence of shoreline sand waves and their characteristics.

4 References

Inman, D. L.; Bagnold, R. A. (1963): Littoral processes in the sea; Volume 3. Interscience, New

York

Baquerizo, A.; Losada, M. A. (2008): Human interaction with large scale coastal morphological

evolution. An assessment of the uncertainty. In: Coastal Engineering, No. 55, pp. 569-

580

Losada, M. A.; Baquerizo, A.; Ortega-Sánchez, M.; Ávila, A. (2011): Coastal evolution, sea

level, and assessment of intrinsic uncertainty. In: Journal of Coastal Research, Special

Issue No. 59.

López-Ruiz, A.; Ortega-Sánchez, M.; Baquerizo, A.; Losada, M. A. (2011): Shoreline sand

wave son curvilinear coasts. Submitted to Journal of Geophysical Research.


Book of Abstracts - Session 3: Coastal Risk / Riskmanagement 35

Turbulent boundary layer under a solitary wave: a RANS model

Giovanna Vittori 1 , Paolo Blondeaux 1

1 Introduction

Recently, Sumer et al. (2010) have carried out accurate laboratory experiments to obtain

quantitative information on the flow generated close to the bottom by the propagation of a

solitary wave. With the same goal, Vittori & Blondeaux (2008, 2011) have studied the same flow

by means of direct numerical simulations (DNS). These investigations have shown that the flow

regime keeps laminar during the whole wave cycle, when the wave amplitude is relatively small

and turbulence appears when the ratio ε between the wave amplitude and the local water depth

is larger than a critical value which depends on the ratio δ between the thickness of the

boundary layer and the water depth. Close to the critical conditions, both Vittori & Blondeaux

(2008, 2011) and Sumer et al. (2010) have shown that the instability of the flow leads to the

appearance of two-dimensional vortices with their axis parallel to the bottom and orthogonal to

the flow direction. For larger values of the wave amplitude, the two-dimensional vortices

become unstable, break-up and generate a turbulent flow. Even though the DNS of Vittori &

Blondeaux (2008, 2011) provide a detailed picture of the flow field, even in the turbulent regime,

the power of actual computers does not allow the use of this approach for engineering

applications. Moreover, the actual numerical techniques does not allow the integration of

continuity and Navier-Stokes equations for the rough wall case. A fair description of the flow at

the bottom of a solitary wave has been obtained by Suntoyo & Tanaka (2009) who used the

two-equation turbulence model of Menter (1994). The model is based on the k-Ω approach in

the region close to the bottom and takes advantage of the robust behaviour of the k-ε model in

the outer part of the boundary layer. However, the model used by Suntoyo & Tanaka (2009)

does not reproduce the well defined second peak of the wall shear stress detected by the

experimental measurements of Sumer et al. (2010). Moreover, the model used by Suntoyo &

Tanaka (2009) gives a critical value of the Reynolds number for turbulence appearance which is

smaller than the value found by Sumer et al. (2010). In the present contribution, the boundary

layer under a solitary wave is investigated by means of the two-equation turbulence model by

Saffman (1970). As pointed out by Menter (1994) this model appears to be superior to other

models close to the bottom. Moreover, some numerical experiments have shown that the

results described in the following do not depend on the details of the asymptotic behaviour of

the pseudo-vorticity far from the wall. The Reynolds stress tensor is expressed in terms of an

eddy viscosity and of the average strain tensor. Then, the eddy viscosity is assumed to be a

function of two turbulence local properties, namely a pseudo-energy e and a pseudo-vorticity Ω,

which are assumed to satisfy nonlinear advection-diffusion equations. The model can describe

both the smooth and rough wall cases and can provide an accurate description of the transition

process from the laminar regime to the turbulent regime (Blondeaux, 1987).

2 The results

When the present model is run for a small value of ε, the eddy viscosity turns out to be

practically zero and the velocity field does not differ from the laminar one. In this case the

bottom roughness does not affect the results. A comparison between the present numerical

results and the analytical solution which holds for the laminar regime shows the accuracy of the

numerical approach. If the value of δ is kept fixed and the value of ε is increased, a critical value

εc is encountered, above which the value of the pseudo-vorticity e grows explosively during the

decelerating phase and the flow regime becomes turbulent. If the value of ε is further increased,

non-vanishing values of e appear earlier and e attains larger values. When turbulence appears,

the momentum mixing induced by turbulent eddies makes the velocity profile smoother than that

characterizing the laminar regime. The flow regimes (laminar/turbulent) determined on the basis

1

Department of Civil, Environmental and Architectural Engineering, University of Genoa, Via Montallegro 1, 16145

Genoa, Italy. blx@dicat.unige.it


36 5th International Short Conference on Applied Coastal Research - SCACR 2011

of the present model are shown in figure 1. Since the value of the eddy viscosity, which is used

to identify the flow regime, is a continuous function of the parameters, to obtain a quantitative

criterion, the flow is defined to be laminar if the maximum value of the ratio between the eddy

viscosity and the fluid viscosity during the wave cycle is smaller than or equal to 1. On the other

hand, if the maximum value is larger than 10, the flow is defined to be turbulent. Values of the

maximum falling between 1 and 10 are supposed to give rise to a transitional regime. Even

though transition to turbulence depends both on ε and δ, for practical purposes it is possible to

approximate transition conditions in terms of an appropriate Reynolds number and results

similar to those of Sumer et al. (2010) are obtained. Finally the model shows that, as found by

Sumer et al. (2010) and Vittori & Blondeaux (2008, 2011), the shear stress attains also negative

values. On the basis of their direct numerical simulations, Vittori & Blondeaux (2011) suggested

heuristic laws to evaluate the maximum positive and negative values of the bottom shear stress.

It can be verified that the present model provides results which are almost coincident with those

of Vittori & Blondeaux (2011).

ε

0.8

0.6

0.4

0.2

laminar

transitional

turbulent

Re=5 10 5

Re=2 10 5

0

0 0.0005 0.001

δ

0.0015 0.002

Figure 1: Flow regimes in the boundary layer at the bottom of a solitary wave (white points =

laminar regime, black points = turbulent regime, black&white points = transitional

regime)

3 Acknowledgements

This study was funded by the 'Ministero dell'Istruzione, dell'Università e della Ricerca' under the

research project 2008YNPNT9-003 'Idrodinamica e morfodinamica nella regione dei frangenti'.

4 References

Blondeaux, P. (1987) Turbulent boundary layer at the bottom of gravity waves. In: J. Hydraulic

Res. 25, No. 4, pp 447-464;

Menter, F.R. (1994) Two-equation eddy-viscosity turbulence models for engineering

applications. In: AIAA J., Vol. 32, No.8, pp. 1598-1605;

Saffman, P.G. (1970) A model for inhomogeneous turbulent flow. In: Proc. R. Soc. London. A

Vol. 317(1530), pp. 417–433;

Sumer, B.M.; Jensen, P.M.; Soerensen, L.B.; Fredsoe, J.; Liu, P.L.F. (2010) Coherent

structures in wave boundary layers. In: J. Fluid Mech., Vol. 646, pp 207-231;

Suntoyo; Tanaka, H. (2009) Numerical modeling of boundary layer flows for solitary waves. In:

J. Hydro-environment Res., Vol. 3, pp 129-137;

Vittori, G.; Blondeaux, P. (2008) Turbulent boundary layer under a solitary wave. In: J. Fluid

Mech., Vol. 615, pp. 433-443;

Vittori, G.; Blondeaux P. (2011) Characteristics of the boundary layer at the bottom of a solitary

wave. In: Coastal Eng., Vol. 58, No. 2, pp. 206-213.


Book of Abstracts - Session 3: Coastal Risk / Riskmanagement 37

Numerical and physical modelling of wave penetration in

Oostende harbour during severe storm conditions

Vincent Gruwez 1 , Annelies Bolle 2 , Toon Verwaest 3 and Hassan Wael 4

1 Introduction

The harbour of Oostende is located on the Belgian coast facing the North Sea. As a part of the

master plan for coastal safety for the Belgian coast, safety measures against flooding during

severe storms are needed in the harbour. Therefore the hydrodynamic boundary conditions

along all the tide and wave afflicted constructions in the inner harbour are required. At the

moment the configuration of the outer harbour is being changed dramatically as the old harbour

dams are replaced by two new rubble-mound breakwaters (cf. Figure 1) and the access channel

is broadened and deepened.

Figure 1: Harbour of Oostende, original harbour dam layout (left), future breakwater layout (right)

The wave penetration is modelled using a physical model and several numerical models

(MILDwave, Mike 21BW and SWAN). A comparative analysis of the results is made and finally

the wave conditions along each structure in the inner harbour are determined.

2 Physical model wave data

The future configuration was modelled in a physical wave basin on a scale of 1:100. Wave

measurements were performed inside the model harbour at more than 20 locations with nondirectional

wave gauges and are used to validate the numerical models. Storm conditions with a

return period of 1000yrs are a water level of 7.0m TAW, significant wave height of 5.0m and

peak wave period of 12.0s and a Jonswap spectrum. Three wave directions were simulated in

the wave basin: NW, NNW and -37° which is the direction for which the most wave energy

penetrates the harbour. In total 47 wave conditions were modelled.

3 Numerical modelling & comparative analysis

Several numerical models are applied to determine the wave conditions in the harbour under

severe storm conditions. Both phase-averaged and phase-resolving numerical wave models are

used, but for different purposes as will be explained.

1

International Marine and Dredging Consultants (IMDC NV), Coveliersstraat 15, 2600 Berchem (Antwerp), Belgium,

vgr@imdc.be

2

International Marine and Dredging Consultants (IMDC NV), Coveliersstraat 15, 2600 Berchem (Antwerp), Belgium,

abo@imdc.be

3

Flanders Hydraulics Research (Waterbouwkundig Laboratorium), Berchemlei 115, 2140 Antwerp, Belgium,

Toon.Verwaest@mow.vlaanderen.be

4

Flanders Hydraulics Research (Waterbouwkundig Laboratorium), Berchemlei 115, 2140 Antwerp, Belgium,

Hassan.Wael@mow.vlaanderen.be


38 5th International Short Conference on Applied Coastal Research - SCACR 2011

The most important physical processes in a harbour are diffraction, depth refraction/shoaling,

(partial) reflection, transmission and non-linear wave-wave interactions (Battjes, 1994). The

phase-resolving numerical models are used for the modelling of wave penetration because they

can simultaneously account for diffraction and reflection (and standing waves) as opposed to

the phase-averaged wave models. A linear time dependant mild-slope equation model

MILDwave (Troch, 1998) and a more complex non-linear Boussinesq equation model Mike

21BW (DHI, 2009) are used. By comparing both models and validation with the physical model

measurements, the applicability of each model is identified.

A severe storm is accompanied by extreme wind speeds, which cause local generation of very

short waves in the harbour. The physical model and both phase-resolving models cannot

account for this process 5 . The spectral model SWAN (TUDelft, 2010) is a phase-averaged wave

model which can model wave generation by wind. Due to the local nature of this process,

diffraction plays a minor role and use of the phase-averaged wave model SWAN is acceptable.

Only wind and no waves are imposed at the model boundary.

The total wave climate on each location in the harbour is obtained by superposition of the wave

penetration wave spectrum and the locally wind-generated wave spectrum. The contribution of

the locally wind-generated waves becomes more important deeper into the harbour, where

wave penetration from outside the harbour is becoming small and locally wind-generated waves

are becoming larger due to the longer travelled fetch length.

Until now only short wave penetration (T < 20s) was considered, but long wave penetration (T >

20s) in Oostende harbour is also of interest. Long waves may lead to resonance and seiching.

Resonance frequencies of the harbour are identified by imposing a fictional ‘white noise’

spectrum (equal amounts of energy at all frequencies) (Gierlevsen, 2001).

4 Resulting boundary conditions inner harbour

Design of the safety measures against flooding is based on a limitation of the overtopping

discharge. Formulas to calculate overtopping require the incoming significant wave height,

direction and extreme water level. The extreme wave heights along the structures in the inner

harbour are determined by superposition of the wave penetration spectrum and locally windgenerated

waves. Determination of the incoming significant wave height and wave direction is

attempted by using the maximum entropy method on the results from the Mike 21BW model, by

investigating the directional wave spectrum from the SWAN model and by analyzing surface

elevation snapshots of the phase-resolving model results. The calculated resonance is added to

the extreme water level to account for the long wave penetration.

5 Acknowledgements

The Flemish government is acknowledged for funding this research.

6 References

Battjes, J.A. (1994): Shallow water wave modelling, M. Isaacson and M. Quick (Eds.), Proc.

Waves-Physical and Numerical Modelling, University of British Columbia, Vancouver.

DHI (2009): Mike 21 BW: Boussinesq Waves Module, Danish Hydraulic Institute.

Gierlevsen, T., Hebsgaard, M., Kirkegaard, J. (2001): Wave disturbance modelling in the port of

Sines, Portugal – with special emphasis on long period oscillations, in: International

Conference on Port and Maritime R&D and Technology (Singapore).

Troch, P. (1998): MILDwave – A numerical model for propagation and transformation of linear

water waves, Internal Report, Department of Civil Engineering, Ghent University.

TUDelft (2010): SWAN (Simulating WAves Nearshore); a third generation wave model

Copyright © 1993-2011 Delft University of Technology.

5 Wind generation of waves is currently under development for MILDwave by the University of Ghent.


Book of Abstracts - Session 3: Coastal Risk / Riskmanagement 39

Numerical simulation for indicator of vulnerability to climate

change on four French beaches

Philippe Larroudé 1 , Déborah Idier 2 and Olivier Brivois 2

1 Abstract

In a context of climate change, we will present the methodology of the modeling approach to

analyze the sensitivity of several beaches of the French coast to forcing conditions changes. All

these studies have been done within the ANR research project called VULSACO. One of the

aims is to set-up vulnerability indicators of sandy beaches against the climate change

predictions for 2030. Models are based on three modules of the Telemac software: current,

wave and bed-evolution. The equations of the three modules are detailed in Hervouet (2007).

This modeling methodology of sandy beaches evolution has already been validated in terms of

mesh, time step and convergence in Falqués et al. (2008) and Larroudé (2008).

The figure 1 shows numerical results versus in situ data on Truc Vert Beach. For other sites see

Maspataud et al. (2010) and ANR-Vulsaco reports (Idier et al., 2010). The physical presentation

of the sites is described in (Maspataud et al. 2009 and 2010, Thiebot et al, 2010, Parisot et al.

2009 and Vinchon et al, 2008, Chateauminois et al, 2010). Simulation results show a

reasonable fit with the data obtained on the beaches.

Figure 1: Time evolution of Hs, Ux (cross shore) and Uy (long shore) measured (VEC3: blue line)

versus numerical (Telemac: red line).

We will present two simple indicator methods to analyze the vulnerability of the four beaches

based on the results of simulations for different scenarios. The first method is based on the

method described in Idier et al. (2006, 2010). In the present study, we calculate the maximum

grain size potentially mobilized but with a simpler approach, based on analysis in different point

on several cross shore profile. The second method which will be presented is the analysis of the

temporal evolution of cross-shore profiles for each site for the same scenarios presented above.

This study shows the possibility and the limitation of these two simple methods to extract

indicator of vulnerability from numerical 2DH simulation.

1

LEGI, BP 53 38041 Grenoble France, larroude@hmg.inpg.fr

2

BRGM Service RNSC,3 av; Guillemin BP 6009 45060 Orléans France


40 5th International Short Conference on Applied Coastal Research - SCACR 2011

2 Acknowledgements

This work has been supported by French Research National Agency (ANR) through the

Vulnerability Milieu and Climate program (project VULSACO, n° ANR-06-VMC-009).

3 References

Chateauminois E., Idier D., Balouin Y., Certain R., Robin N., Crillon J., Maanan M., Parisot J.P.,

Rihouey D., Robin M., Ruz M., Maspataud A., Hequette A, (2010) – Projet VULSACO.

Vulnérabilité de plages sableuses face au changement climatique et aux pressions

anthropiques. Module 2.1 : Analyse des tendances. Rapport final.

Falqués A., Dodd N., Garnier R., Ribas F., MacHardy L.C., Sancho F., Larroudé Ph. and

Calvete D., 2008, Rhythmic surf zone bars and morphodynamic self-organization,

Coastal Engineering 55, pp 622–641.

Hervouet, J.M., Hydrodynamics of Free Surface Flows: Modelling With the Finite Element

Method, 2007, John Wiley & Sons, 360p.

Idier D., Pedreros R., Oliveros C., Sottolichio A., Choppin L. et Bertin X., (2006), Contributions

respectives des courants et de la houle dans la mobilité sédimentaire d’une plateforme

interne estuarienne. Exemple : le seuil interinsulaire, au large du Pertuis d’Antioche,

France. C .R. Geoscience, Vol. 338, 718-726.

Idier D., Romieu E., Pedreros R. and Oliveros C., 2010, A simple method to analyse noncohesive

sediment mobility in coastal environment. Continental Shelf Research 30, pp

365–377.

Idier D., Bouchette F., Brivois O., Castelle B., Certain R., Chateauminois E., Delvallée E.,

Héquette A., Larroudé P., Maanan M., Maspataud A., Parisot J.P., Pedreros R., Robin

N., Romieu E., Ruz M., Thiébot J. (2010a) - Projet VULSACO. Vulnérabilité de plages

sableuses face au changement climatique et aux pressions anthropiques. Module 3.2 :

Modélisation de la dynamique actuelle et future des plages. Rapport final, BRGM/RP-

58919-FR. Accès public : 01/01/2012.

Larroudé Ph., 2008, Methodology of seasonal morphological modelisation for nourishment

strategies on a Mediterranean beach. Marine Pollution Bulletin 57, pp 45-52.

Maspataud A, Ruz, M-H., and Héquette, A. Spatial variability in post-storm beach recovery

along a macrotidal barred beach, southern North SeaICS2009. Lisbon, Portugal. 13-18

April 2009. Journal of Coastal Research, proceedings of ICS 2009

Maspataud A., Idier D., Larroudé Ph., Sabatier F., Ruz M.H., Charles E., Levacheux S.,

Hequette A., L’apport de modèles numériques pour l’étude morphodynamique d’un

système dune-plage macrotidal sous l’effet des tempêtes : plage de la dune Dewulf, Est

de Dunkerque, France, (pp. 353-360), DOI:10.5150/jngcgc.2010.042-M

Parisot J.P., Capo S., Castelle B., Bujan S., Moreau J., Gervais M., Réjas A., Hanquiez V.,

Almar R., Marieu V., Gaunet J., Gluard L., George I., Nahon A., Dehouck A., Certain R.,

Barthe P., Le Gall F., Bernardi P.J., Le Roy R., Pedreros R., Delattre M., Brillet J. and

Sénéchal N. (2009). “Treatment of topographic and bathymetric data acquired at the

Truc-Vert Beach (SW France) during the ECORS mission”. J. of Coastal Res., ICS

2009.

Thiébot, Robin, Garnier, Certain, Idier, Calvete, Falquès, and Levoy Morphological response of

a double nearshore bar system under oblique Geophysical Research Abstracts, Vol. 11,

EGU General Assembly 2009.

Vinchon C., Idier D., Balouin Y., Capo S., Castelle B., Chateauminois E., Certain R., Crillon J.,

Fattal P., Hequette A., Maanan M., Mallet C., Maspataud A., Oliveros C., Parisot J.P.,

Robin M., Ruz M., Thiebot J. (2008) - Projet VULSACO. Vulnérabilité de plages

sableuses face au changement climatique et aux pressions anthropiques. Module 1 :

Caractérisation des sites. Rapport final, BRGM/RP-56618-FR, 114 p., 48 fig., 16 tabl., 7

ann.


Book of Abstracts - Session 3: Coastal Risk / Riskmanagement 41

Coastal long term processes, tidal characteristics and climate

change

Hartmut Hein 1 , Stephan Mai and Ulrich Barjenbruch

1 Background: Global Climate Change and regional impact

It is widely accepted, that the climate-related sea level rise (SLR) influences the long-term

coastal processes. An almost linear rise of about 1-2 mm per year has already been observed

in this region (Wahl, 2010). A future acceleration is expected (IPCC, 2007). Sensitivity studies

(e.g. Mai, 2004a, b) show a variation of tidal water levels, of significant wave heights or also the

morphology at the North Sea coast as a result of a changing climate. The predominant process,

influencing most other parameters is the change of the tidal characteristics. Besides of climate

change, long term processes influence the regional tidal characteristics, which for example

impact the sedimentation (Oost et al. 1993). Therefore, one possibility, to draw conclusions for

the future changes of the tidal characteristics, is to examine gauging data, in order to deriving

the recent rise of sea level. However, an extrapolation of SLR is difficult, because of its nonlinearity.

The second possibility is the use of a model chain, to transfer the results of global

climate models into results for the coastal areas.

2 Analysis of the model-chain

The modal chain used in the research program KLIWAS (Mai et al. 2009) of the German

Federal Ministry of Transport, Building and Urban Development, by the Federal Institute of

Hydrology together with several partners is given in Figure 1. The model chain from the

scenario towards the long term simulations of the German North Sea estuaries is shown. The

model chain starts with different emission scenarios. These are used to run various global

climate models, to derive atmospheric and oceanographic parameters on a global scale.

Secondly, it is necessary to transform the results of global climate models with regional

downscaling into results for the region. This is usually done with the uncoupled models of ocean

and atmosphere. In KLIWAS we also test coupled models on the regional scale. To get from a

regional scale to a particular stretch of coastline, we applied numerical models for the estuaries.

The whole model chain is used to simulate a climate-relevant period. For this reason simple

and fast models, which are able to reproduce baroclinic processes (Hein, 2007), are used.

Within the model chain, the lack of tidal information in most climate models, is a challenge.

Thus, we use additional global models of tides. It must be ensured for the sea-state, that the

influence is considered, which is caused by the changing characteristics of future tide (Hein,

2010b). The model chain is tested by hindcasting the recent climate and by comparing hindcast

results with measurement. An analysis of the model chain shows that there is only small

influence originating form the emissions scenarios on SLR. Further analysis of the model chain

shows that global climate models provide realistic simulations only for a number of key aspects

of natural internal variability, which we observed by measurements. However, this natural

internal variability is the major factor of uncertainty in the observed sea level rise in the southern

North Sea (Hein, 2010a). On the North Sea scale, some tests of coupled regional models done

by Schrumm (2001) indicate that the results of global models are inadequate to reproduce the

regional sea level in a deterministic way – independent if the models are coupled or not.

3 Conclusion

The results of our model chain are therefore analyzed with stochastic and probabilistic methods.

We analyze long term averages and their statistics form both observations and simulations. Our

research shows that, due to the large uncertainties in the model chain, it is necessary to look

1 Federal Institute of Hydrology, Am Mainzer Tor 1, 56068 Koblenz, hein@bafg.de


42 5th International Short Conference on Applied Coastal Research - SCACR 2011

exactly, what “information" still exist. It should be noted, that the description of many physical

changes suffers. We discuss to add them synthetically.

4 Tables and Figures

Figure 1: Model-chain from emission scenarios towards the coastal processes.

Acknowledgements

KLIWAS is funded by Federal Ministry of Transport, Building and Urban Development

5 References

Hein, H., Karfeld, B., Pohlmann, T., 2007: Mekong water dispersion: Measurements and

consequences for the hydrodynamic modelling, Journal of Water Resources and

Environmental Engineering, Special Issue, August 2007, 21 – 28.

Hein, H., Weiss, R., Barjenbruch, U., Mai, S., 2010a: Uncertainties of Tide gauges and the

estimation of Sea Level Rise, Proceedings of the Hydro2010, Warnemünde.

Mai, S., 2004a: Klimafolgenanalyse und Risiko einer Küstenzone am Beispiel der Jade-Weser-

Region.Von dem Fachbereich Bauingenieur- und Vermessungswesen der Universität

Hannover genehmigte Dissertation, 391 S., Hannover, 2004 (auch in: Mitteilungen des

Franzius-Instituts, H. 91, S. 1 - 275, Hannover, 2004).

Mai, S., Stoschek, O., Geils, J., Matheja, A., 2004b: Numerical Simulations in Coastal

Hydraulics & Sediment Transport. Proc. of the NATO Advanced Research Workshop

(ARW), S. 149 - 169, Varna, Bulgaria, 2004.

Mai, S., Heinrich, H., Heyer, H., 2009: Das hydrologische System der Wasserstraßen im

Küsten- und Ästuarbereich - KLIWAS-Vorhaben 2.Tagungsband des 1. KLIWAS-

Statusseminars 17.03.2009, S. 36 - 41, Bonn.

Oost, A.P., H. de Haas, F. Ijnsen, J.M. van den Boogert, P.L. de Boer, 1993: The 18.6 yr nodal

cycle and its impact on tidal sedimentation, Sedimentary Geology, Volume 87, Issues 1-

2, September 1993, Pages 1-11.

Schrum. C., 2001: Regionalization of climate change for the North Sea and Baltic Sea. Climate

Research, 18, 31-37.

Wahl, T.; Jensen, J.; Frank, T., 2010, “On analysing sea level rise in the German Bight since

1844”, Natural Hazards and Earth System Science, Volume 10, Issue 2, pp.171-179.


Book of Abstracts - Session 3: Coastal Risk / Riskmanagement 43

Coastal flooding risk at the city of Oostende

Niels Balens 1,2 , Xavier Valls 1,2 , Johan Reyns 1 , Toon Verwaest 1 , Stefaan Gysens 3

1 Introduction

Oostende is the largest city at the Belgian North Sea coast. The city of Oostende is one of the

weak links in the Belgian coastal defence line. On the one hand the sea dike promenade is

relatively low and narrow and also there are many pathways of flooding over low-lying quay

areas and low-crested structures in the harbour area. On the other hand the consequences of a

flooding are high because of the dense population and the high values of infrastructure in the

city as well as in the port. To strengthen the weak links in the Belgian coastal defence line at

Oostende, an integrated coastal and maritime plan is established and under construction at

present and for the coming years (Gysens et al, 2010). Also non-structural risk management

measures are being worked out, such as evacuation plans. The basis for the design of these

structural and non-structural measures are flood risk calculations (Mertens et al, 2010).

2 General methodology of the coastal flood risk calculations

The coastal flood risk calculation methodology is determined starting from the Flemish risk

calculation method used along the waterways, but taking into account all typical coastal

phenomena (Verwaest et al, 2008). Typical coastal issues are:

� Erosion of beaches and dunes

� The large wave overtopping discharges in the coastal towns with possible

consequences for the buildings and people living at the seaside promenades as

well as possible breaching in coastal towns where the low-lying coastal plain is

situated very near to the sea dike

� Flooding by a combination of overflow and overtopping at quay areas and lowcrested

structures in coastal harbours; in some cases also possibility of breaching

of some of these low-crested structures

� Large scale flooding of the low-lying coastal plain

� Relatively low probability of occurrence but high consequences

Coastal risk at the Belgian coast is calculated by simulating economic damages and human

casualties for a set of four representative extreme storm surges with surge levels +6,5 m TAW,

+7 m TAW, +7,5 m TAW, +8 m TAW at Oostende and with return periods anno 2000

respectively 110 year, 740 year, 4000 year, 17000 year. A chain of numerical models is

followed starting from wave propagation simulations towards the coastal defence line -including

the harbour areas-, overtopping and overflow calculations following state of the art empirical

formulas, breach modelling using the Visser-Kortenhaus theory simulating landward erosion of

the core using the parameterization by Visser (2002) adapted for the intermittent nature of flow

in case of overtopping by Kortenhaus (2003), 2D flooding of the coastal plain, and finally a GISbased

modelling to estimate direct economic damages and probabilities of human casualties in

relation to the maximum water levels and velocities occurring during the flooding. For the

special case of risks for buildings and people living on the seaside promenades the formulas for

the velocity and the thickness of the overtopping layer which were proposed by Schüttrumpf

(2001) are used in combination with specific damage/casualties curves.

1 Flanders Hydraulics Research, Berchemlei 115, 2140 Antwerp, Belgium, toon.verwaest@mow.vlaanderen.be

2 Research unit Coastal Engineering Ghent University, Technologiepark 9, 9052 Ghent, Belgium

3 Agency for Maritime and Coastal Services, Coast Division, Vrijhavenstraat 3, 8400 Oostend, Belgium,

stefaan.gysens@mow.vlaanderen.be


44 5th International Short Conference on Applied Coastal Research - SCACR 2011

3 Application for Oostende

The city of Oostende is vulnerable for coastal flooding, on the one hand because large areas

are low-lying (see Figure 1) and on the other hand because of many homes and important

infrastructure on the coastal defences themselves e.g. on the seaside promenades.

Figure 1: Plan of the Oostende area with information on the height of the terrain

4 Acknowledgements

The authors acknowledge the German and Dutch coastal engineering colleagues for their

scientific work on coastal risk which was proven applicable also for the Belgian coast.

5 References

Gysens S., De Rouck J., Trouw K., Bolle A., Willems M. (2010): Integrated coastal and maritime

plan for Oostende: design of soft and hard coastal protection measures during the EIAproces,

in: Proceedings of the 32st International Conference on Coastal Engineering

2010, 30 June – 5 July 2010, Shanghai, China.

Kortenhaus A. (2003): Probabilistische Methoden für Nordseedeiche, Leichtweiß-Institut für

Wasserbau, Technische Universität Braunschweig, PhD thesis.

Mertens T., Verwaest T., Delgado R., Trouw K., De Nocker L. (2010): Coastal management and

disaster planning on the basis of flood risk calculations, in: Proceedings of the 32st

International Conference on Coastal Engineering 2010, 30 June – 5 July 2010,

Shanghai (China).

Schüttrumpf H. (2001): Wellenüberlaufströmung bei Seedeichen -Experimentelle und

theoretische Untersuchungen-, Leichtweiß-Institut für Wasserbau, Technischen

Universität Braunschweig, PhD thesis.

Verwaest T., Van der Biest K., Vanpoucke P., Reyns J., Vanderkimpen P., De Vos L., De Rouck

J., Mertens, T. (2008). Coastal flooding risk calculations for the Belgian coast, in:

Proceedings of the 31st International Conference on Coastal Engineering 2008, 31

August – 5 September 2008, Hamburg (Germany), pp. 4193 – 4201.

Visser P. (2002): Breach growth in sand-dikes, TU Delft, PhD thesis.


Book of Abstracts - Session 3: Coastal Risk / Riskmanagement 45

Parameterization of storm surges as a basis for assessment of

risks of failure for coastal protection measures

Dörte Salecker 1 , Angelika Gruhn 1 , Christian Schlamkow 1 and Peter Fröhle 1

1 Objective

Coastal structures protect large areas of the German North Sea and Baltic Sea Region. The

failure of those structures would lead to the inundation of approximately 12.000 km² of low lying

land and would therefore cause major damage along the coast line. To detect sizes of

potentially flooded areas as well as potential losses, arising from the event, a joint research

project “HoRisK – Flood Risk Management in Coastal Areas” is conducted.

Together with the project partners, RWTH Aachen University, NLWKN (Lower Saxony Water

Management, Coastal Defence and Nature Conservation Agency) Norden and LKN (Schleswig-

Holstein Federal Agency for Coastal and Nature Protection) Husum as well as StALU

(Mecklenburg-Vorpommern Federal Agency for Agriculture and Environment) Rostock, the

Coastal Engineering Group of the University of Rostock (URCE) is participating in the project.

Within the HoRisK project, methods for application-orientated flood damage- and flood risk

analyses will be developed. Those methods provide a basis for the creation of “Flood hazard

maps”, “Flood risk maps” as well as “Flood risk management plans”, which have to be

developed by the member states to fulfil the requirements of the “Directive of the European

parliament and the council on the assessment and management of flood risk” (2007/60/EC).

2 Methodology

Hydrodynamic forces that affect coastal structures and might cause their failure, may result from

high water levels, local sea state, currents and at least partly from ice drift, also their combined

occurrence has to be considered. In the course of the HoRisK project, the emphasis is put on

analysing water levels as well as the sea state, since currents and ice drift are of minor

importance both, in the German Baltic Sea and in the German North Sea.

In order to detect sizes of potentially flooded areas as well as the water depth, numerical

models are being used. Those models require storm surge hydrographs with a constant

temporal resolution as input data.

To gain storm surge hydrographs from water levels, which are measured hourly, in a first step

different methods are applied to create samples of water levels. Deriving from the time series of

measured water levels, areas of storm surge hydrographs are determined.

Univariate extreme value models (Weibull distribution, Log-Normal distribution, Generalised

Extreme Value distribution, Gumbel and Generalised Pareto distribution) are fitted to samples of

both water levels and areas of storm surge hydrographs.

As past experiences have shown, the failure of coastal structures might occur even though

water levels are moderately high, if the duration of the storm surge is long. Hence, it is obviously

necessary to include durations of extreme events and combinations with other hydrodynamic

impacts in the statistical analyses in order to define critical impacts on coastal structures. Joint

probabilities of two or more forces on coastal structures can be characterized by combined

univariate analyses or bivariate and multivariate analyses.

In the context described in the paper, bivariate statistical models, namely copula functions (e.g.

Clayton, Frank and Gumbel families), are applied to describe the combined probability of

1 University of Rostock, Institute of Environmental Engineering, Coastal Engineering Group; Justus-von-Liebig-Weg 6,

D18059 Rostock; Email: doerte.salecker@..., angelika.gruhn@..., christian.schlamkow@..., peter.froehle@unirostock.de


46 5th International Short Conference on Applied Coastal Research - SCACR 2011

occurrence of simulated data pairs of water levels and areas of storm surge hydrographs, as

shown in figure 1 (left) for the location Rostock-Warnemünde.

Figure 1: Copula with isolines of equal probability of exceedance (left), Storm surge hydrographs

with a return period of 200 years (right)

In a second step, several methods are reviewed to define various dimensionless shapes of

storm surge hydrographs. Determined dimensionless storm surge hydrographs are scaled to

create a multitude of storm surge hydrographs including high water events with short durations

as well as events with long durations as input data for following numerical simulations (figure 1

(right)).

3 Conclusion

In the paper, main results of statistical analyses of water levels, different parameterization

methods of storm surge hydrographs and the combination of both will be given. The influence of

sampling methods and distribution functions on results of the statistical analyses will be shown

for the univariate as well as the bivariate case. Furthermore, different methods to create storm

surge hydrographs based on parameterized storm surges as input data for numerical

simulations will be presented and compared.

4 Acknowledgements

The HoRisK project is funded by the Federal Ministry for Education and Research and

supported by KFKI (German Coastal Engineering Research Council).

5 References

Klein, B. (2009): Ermittlung von Ganglinien für die risikoorientierte Hochwasserbemessung von

Talsperren. Bochum, Germany: Ruhr-Universiät Bochum, Ph.D. thesis.

ISSN 0949-5975.

Sackl, B. (1987): Ermittlung von Hochwasser – Bemessungsganglinien in beobachteten und

unbeobachteten Einzugsgebieten. Graz, Austria: Technische Universität Graz, Ph.D.

thesis

Salvadori, G., De Michele, C., Kottegoda, N. T. and Rosso, R. (2007): Extremes in Nature - An

Approach Using Copulas. Springer-Verlag Dordrecht, Netherlands.

ISBN 978-1-4020-4414-4.


Book of Abstracts - Session 3: Coastal Risk / Riskmanagement 47

Integrated risk analysis for extreme storm surges (XtremRisK)

Hocine Oumeraci 1 , Jürgen Jensen 2 , Gabriele Gönnert 3 , Andreas Kortenhaus 1 , Andreas Burzel 1 ,

Marie Naulin 1 , Dilani Dassanayake 1 , Thomas Wahl 2 , Christoph Mudersbach 2 , Kristina Sossidi 3 ,

and Gehad Ujeyl 4

1 Introduction

The joint research project XtremRisK (Extreme Storm Surges at Open Coasts and Estuarine

Areas – Risk Assessment and Mitigation under Climate Change Aspects, see also

www.xtremrisk.de) is aiming to improve the understanding of extreme storm surges and related

risks which may result from expected climate change. The XtremRisK project brings together

scientists from three universities in Germany (Braunschweig, Hamburg-Harburg and Siegen)

and the Agency of Roads, Bridges and Water Hamburg, and works in close collaboration with

responsible coastal and harbour authorities. The project started in October 2008 and will be

completed in June 2012 (Oumeraci et al., 2009).

The overall aim of the project is to enhance the knowledge with respect to the uncertainties of

extreme storm surge predictions as well as to quantify the overall flood risks for two selected

pilot sites in Germany representing open coasts (Island of Sylt) and estuarine areas (Hamburg).

In XtremRisK, flood risk is defined as the product of the probability of a flooding event due to an

extreme storm surge and related expected damages. For the integrated risk analysis, a sourcepathway-receptor

concept (see Oumeraci, 2004) is used, which was successfully applied in the

European research project FLOODsite. Hence, the integrated risk analysis comprises the

prediction of extreme storm surges (risk sources), defence failure probabilities (risk pathways)

and the determination of subsequent losses (risk receptors). According to this structure as seen

in Fig. 1, XtremRisK consists of four subprojects (SP), from which subproject 4 (SP4) aims at

performing an integrated risk analysis by merging results achieved in SP1 (determination of

extreme storm surges), SP2 (estimation of defence failure probabilities) and SP3 (modelling of

inundation and damages) (Burzel et al., 2010).

Figure 1: Source-Pathway-Receptor-Concept in XtremRisK

2 Methods and Results

In XtremRisK different extreme storm surge scenarios under current and future climate change

conditions are analysed. In order to enhance knowledge about risk sources, the analysis of the

1 Leichtweiß-Institute for Hydraulic Engineering and Water Resources, Technische Universität Braunschweig,

Beethovenstr. 51a, 38106 Braunschweig, Germany, h.oumeraci@tu-braunschweig.de

2 Research Institute for Water and Environment, University of Siegen

3 Agency of Roads, Bridges and Water, Hamburg

4 Department of River and Coastal Engineering, Hamburg University of Technology


48 5th International Short Conference on Applied Coastal Research - SCACR 2011

physical characteristics of extreme storm surges is essential. The objective is to investigate

extreme values of the storm surge components wind surge, tide and external surge and their

nonlinear interaction (Sossidi et al., 2010). To estimate the occurrence probability for each

scenario, a methodology based on multivariate statistics has been developed (Wahl et al.,

2010). Furthermore, a numerical model has been developed to calculate water and wave

conditions close to the flood defence facilities (Ujeyl et al., 2010).

Analysing the risk pathway, the loading and the stability of the flood defence structures are

determined (Naulin et al., 2010). For a probabilistic reliability analysis failure modes of defences

and the uncertainties of model and input parameters are investigated. Using a fault tree

approach the failure probabilities are calculated for the whole flood defence system. Moreover,

breach modelling of dikes and dunes is performed. As a result, the breach development can be

described and an outflow hydrograph at the breach location is determined which will be used as

an initial condition of the flood wave propagation in the hinterland.

Following, two dimensional numerical flood simulations are performed using the open source

platform Kalypso•RMA to determine the inundation of the hinterland for each storm surge

scenario. The results are used for the analysis of the risk receptors. Hereby, tangible and

intangible losses are considered, i.e. damages on residential and industrial buildings, private

property, industrial goods, and cultural losses as well as the estimation of injuries and fatalities

within the pilot site. The high resolution spatial analysis is carried out by comprehensive

geoprocessing models in ArcGIS. Finally tangible and intangible damages will be integrated

under consideration of the probability for each scenario. Therefore, integration approaches have

been investigated. As a result, the overall flood risk will be quantified in order to develop flood

risk reduction measures.

The XtremRisK project, the developed methodology as well as intermediate results from each

subproject will be presented at the conference.

3 References

Burzel, A., Dassanayake, D.R., Naulin, M., Kortenhaus, A., Oumeraci, H., Wahl, T.,

Mudersbach, C., Jensen, J., Gönnert, G., Sossidi, K., Ujeyl, G., and Pasche, E. (2010):

Integrated Flood Risk Analysis for Extreme Storm Surges (XtremRisK). Proceedings of

the 32nd International Conference on Coastal Engineering (ICCE) 2010, Shanghai,

China, 12p.

Naulin, M., Kortenhaus, A., Oumeraci, H. (2010): Failure Probability of Flood Defence

Structures/ Systems in Risk Analysis for Extreme Storm Surges. Proceedings 32nd

International Conference Costal Engineering (ICCE), Shanghai, China.

Oumeraci, H. (2004): Sustainable coastal flood defences: scientific and modelling challenges

towards an integrated risk-based design concept. Proc. First IMA International

Conference on Flood Risk Assessment, IMA - Institute of Mathematics and its

Applications, Session 1, Bath, UK, pp. 9-24.

Sossidi, K., Gönnert, G., Gerkensmeier, B. (2010): The risk and calculation of extreme storm

surges due to climate change. Presentation on the Storm Surges Congress (SSC) 2010

– Risk and Management of current and future Storm Surges, Hamburg, Germany.

Ujeyl, G., Pasche, E., Gershovich, I. (2010): Determination of significant waterstage and wave

heights of the Elbe estuary in the area of Hamburg using a hydrodynamic 2D model.

Presentation on the Storm Surges Congress (SSC) 2010 – Risk and Management of

current and future Storm Surges, Hamburg, Germany.

Wahl, T., Jensen, J., Mudersbach, C. (2010): A multivariate statistical model for advanced storm

surge analyses in the North Sea. Proceedings of the 32nd International Conference on

Coastal Engineering (ICCE) 2010, Shanghai, China, 12p.


Book of Abstracts - Session 3: Coastal Risk / Riskmanagement 49

Implementing coastal defence strategies for sandy coasts –

reinforcement of the Norderney dune revetment

Frank Thorenz 1 , Holger Blum 2

1 Introduction

The sandy barrier island of Norderney is one of seven inhabited islands located in front of the

mainland coast of the German Federal State Lower Saxony, representing nowadays important

sea resorts [Thorenz, 2006]. The western part of Norderney is protected by dune revetments,

groins and beach nourishments against erosion and flooding. Due to increasing damages of the

revetment even in minor storm surges, the Lower Saxony Coastal Defence, Water Management

and Nature Conservation Agency (NLWKN) investigated the functionality of the revetment.

Model tests showed the necessity to rebuild significant sections of the revetment. Limited available

space as well as demands of tourism are to be considered.

2 Initial state of the construction

The initial construction of the Norderney dune revetment was build 1857/58 in order to protect

the expanding city against increasing erosion. Until the end of the 20th century, several reinforcements

and extensions of the revetment mainly due to damages in severe storm surges

were executed, leading to a construction consisting several sections and a crest height of 8.5 m

above NN (German datum level), whereas design water level is 5.0 meter NN [Fig. 1].

Figure 1: Typical cross section of the initial dune revetment at Norderney

3 Coastal defence strategy, legal and spatial boundary conditions

The Lower Saxony coastal defence strategy and legal boundary conditions are stated in the

Master Plan Coastal Defence [NLWKN, 2010]. In case of structural eroding coasts and high

vulnerability such as the western part of Norderney the strategy of preservation of the existing

coastline and protection against flooding is implemented. Technical means are groins and revetments

as well as additional beach nourishments. Due to historical reasons, areas with very

small distances of revetment crest to the adjacent buildings exist.

4 Investigation of hydrodynamical loading

In order to determine design parameters for the construction, combined numerical and hydraulical

model tests were performed yielding significant wave heights up to Hs = 3.5 m and wave

periods up to Tm-1,0 = 10 s for design conditions [Niemeyer et. al., 2000]. Overtopping rates of

1 Lower Saxony Water Management, Coastal Defence and Nature Conservation Agency (NLWKN), Jahnstr.1, D-26506

Norden, Germany, frank.thorenz@nlwkn-nor.niedersachsen.de

2 Lower Saxony Water Management, Coastal Defence and Nature Conservation Agency (NLWKN), Jahnstr.1, D-26506

Norden, Germany, holger.blum@nlwkn-nor.niedersachsen.de


50 5th International Short Conference on Applied Coastal Research - SCACR 2011

more than 120 l/s.m and maximum pressures of 200 kPa resulted of hydraulical model tests

[Schüttrumpf et al., 2001] and showed the need for reinforcement.

5 Results of planning

General planning goals were the reduction of wave loading as well as limitation of wave run-up

and overtopping in order to reduce the hazard of flooding. Due to the nearness of nonremovable

buildings and therefore very limited space, special construction elements were

needed: A new granite revetment with slopes milder than 1 : 3, berms and additional roughness

elements are integrated in the construction. For a more than 400 m long section, two types of

combinations between wall elements located behind the upper berm and crest walls were designed

[Fig. 2-4]. Gaps between the elements provide backflow of water overtopping the wall

elements. Needs of tourism and urbanistic aspects were integrated in the design of the walls

and the surrounding revetment. Similar constructions are currently under investigation for the

dune revetment at the island of Baltrum located eastward Norderney [Liebisch et al. 2011].

Figures 2, 3 and 4: Cross section with wall elements - summertime and storm surge conditions

6 References

Liebisch, S.; Kortenhaus, A.; Oumeraci, H.; Thorenz, F.; Blum, H. (2011): Wellenüberlauf und

welleninduzierte Belastung des Deckwerks auf der Insel Baltrum, in: Tagungsband 8.

FZK-Kolloquium, pp. 69-74. ISSN 1610-5249. Hannover, Germany.

Niemeyer, H. D.; Kaiser, R.; Weiler, B. (2000): Bemessungsseegang für die Deckwerke am

Nordweststrand von Norderney, internal report.

NLWKN (2010): Generalplan Küstenschutz Niedersachsen – Ostfr. Inseln. Norden, Germany.

Schüttrumpf, H.; Oumeraci, H.; Thorenz, F.; Möller, J. (2001): Reconstruction and rehabilitation

of a historical seawall at Norderney, in: Proceedings ICE Int. Conference Breakwaters,

coastal structures and coastlines,.pp. 257-268. Thomas Telford, London, UK.

Thorenz, F. (2006): Coastal defence strategies as a building block for integrated coastal zone

management. Proc. Third Chinese-German Joint Symposium on Coastal and Ocean

Engineering, pp. 463-472. ISBN-13 957-986-00-7143-6. Tainan, Taiwan.


Book of Abstracts - Session 4: Coastal and Port Environments 51

Physical modelling of brine discharges from a cliff

Macarena Rodrigo 1 , Francisco Vila 2 , Antonio Ruiz-Mateo 3 , Ana Álvarez 4 , Ana Lloret 5 , Manuel

Antequera 6

1 Abstract

The sea water desalination process is a strong bet for developing regions like the Spanish

Mediterranean, to satisfy the increasing fresh water demand, or the Canary Islands, being the

desalination the most important artificial water resource.

The main characteristic of the waste brine disposal resulting from the desalination process is its

high salinity, and consequently, its higher density in comparison with that of the environment.

Therefore, the discharge of the concentrated effluent into the sea may cause a negative impact

in the sea water quality and its ecosystems, particularly regarding the sea grass meadows that

cover the Mediterranean coast.

In order to make the development of the desalination plants sustainable, the Spanish Ministry of

the Environment and Rural and Marine Affairs agreed to invest in Experimental Development

Projects within its National Plan for Scientist Research, Development and Technological

Innovation. The project entitled “Development and implementation of a methodology to reduce

the environmental impact of brine discharges from desalination plants” has been approved and

supported as part of the Plan. This project is being carried out by the University of Cantabria

and the Spanish Centre for Experimentation on Public Works (CEDEX).

The conclusions obtained with the performed physical model will be presented in this

communication since the brine discharge is a hypersaline effluent, with higher density than the

medium, which spreads along the bottom and it can cause harmful effects on marine

ecosystems.

2 Introduction

The aim of this study is to find a methodology to reduce the environmental impact on the

biocenosis as much as possible. Under this perspective the brine discharges were investigated

from three different view points: physical modelling, field works and mathematical modelling.

Depending on the chosen disposal system, the behaviour of the brine effluent, mixing and

dilution with seawater are influenced in different ways. Under this perspective it is proposed to

investigate different discharge devices in physical models.

Physical models are useful tools to improve the desalination plants discharge conditions as well

as to calibrate mathematical models since they allow the evaluation of the effectiveness of their

discharge designs and to choose the most appropriate one. The case of study focuses on the

discharges from a cliff to show some results obtained with the performed physical model.

1 Centre for Studies Ports and Coast of CEDEX, Antonio López, 81, 28026, Madrid, Spain, macarena.rodrigo@cedex.es

2 Centre for Studies Ports and Coast of CEDEX, Antonio López, 81, 28026, Madrid, Spain, francisco.vila@cedex.es

3 Centre for Studies Ports and Coast of CEDEX, Antonio López, 81, 28026, Madrid, Spain, antonio.ruiz@cedex.es

4 Centre for Studies Ports and Coast of CEDEX, Antonio López, 81, 28026, Madrid, Spain, ana.alvarez@cedex.es

5 Centre for Studies Ports and Coast of CEDEX, Antonio López, 81, 28026, Madrid, Spain, ana.lloret@cedex.es

6

Centre for Studies Ports and Coast of CEDEX, Antonio López, 81, 28026, Madrid, Spain,

manuel.antequera@cedex.es


52 5th International Short Conference on Applied Coastal Research - SCACR 2011

3 Physical Model

The experiments have been performing in a flume of 22m long, 1m wide and 2m high with a 2%

fixed slope. The different simulations carried out in this flume were chosen according to a fixed

flow changing some variables such as height and width overflow, and depth.

To this purpose, different instrumentation has been used to measure conductivity and velocity

within the near field of the effluent, including a Micro Scale conductivimeter and Temperature

Instrument, a Doppler Velocity Profiler and several set of pipettes connected to peristaltic

pumps which were positioned at a given distance from the discharge point. Using this

instrumentation, the main measurements to be taken into account refer to the characteristic

positions for this type of discharge: the instantaneous and statistical measurement of the

conductivity for these points, the thickness of the homogeneous and interface layer as well as

the adjustment for the width of the brine discharge along the representative points. All these

measurements are given for each test performed and are compared each other and with the

different instrumentation used.

4 References

Centre for Studies on Ports and Coast (2009): Behaviour of rejection water discharged into the

sea from the desalination plant of Melilla. Final report. CEDEX, Technical Report 23-

403-1-005. In Spanish.

Centre for Studies on Ports and Coast (2003): Research on discharge into the sea of rejection

water from desalination plants. Final report. CEDEX, Technical Report 23-500-7-005. In

Spanish.

Vila, F.; Ruiz-Mateo, A.; Rodrigo, M.; Álvarez, A.; Antequera, M.; Lloret, A. (2010): 3D Physical

Modelling in a wave flume of brine discharges on a beach, in Proceedings of the

Euromed 2010 - Desalination for Clean Water and Energy, Com. 21. Tel Aviv, Israel.

Ruiz-Mateo, A.; Antequera, M.; González, J. (2008): Physical modelling of brine discharges to

the sea, in Proceedings of the MWWD 2008 – 5th Internacional conferences on Marine

Waste Water Discharges and Coastal Environment, Com 65. Cavtat, Croatia.

Palomar, P.; Ruiz-Mateo, A.; Losada, I. J.; Lara, J. L.; Lloret, A.; Castanedo, S.; Alvárez, A.;

Méndez, F.; Rodrigo, M.; Camus, P.; Vila, F.; Lomónaco, P.; Antequera, M. (2010):

MEDVSA: a methodology for design of brine discharges into seawater. In: Desalination

and Water Reuse, Vol. 20/1, pp. 21-25.

Sánchez Lizaso, J.; Romero, J.; Ruiz, J.; García, E.; Buceta, J.; Invers, O.; Férnandez, Y.; Mas,

J.; Ruiz-Mateo, A.; Manzanera, M. (2008): Salinity tolerance of the Mediterranean

seagrass Posidonia oceanica: recommendations to minimize the impact of brine

discharges from desalination plants. In Desalination, Vol. 221, pp. 602-607.


Book of Abstracts - Session 4: Coastal and Port Environments 53

Monitoring of psammitic nearshore bedforms, their evolution

and role as benthic habitat

Ulrich Floth 1

1 Introduction

All along sand dominated shallow water coasts which are not densely occupied by vegetation,

ripple bedforms can be observed, resulting from water currents running over them. According to

their genesis, these bedforms can be can be distinguished into two categories: Current ripples,

shaped under approx. unidirectional currents as well as oscillatory ripples forming under

contrarious and oscillating crurrents. These bedforms furthermore represent a habitat to

numerous endo- and epibenthic organisms like e.g. Mya arenaria, which are strongly influenced

by sediment transport processes around them. These processes and the response of the

organisms are in the focus of this interdisciplinary research issue in the intersection of

geoscience, marine biology and coastal engineering.

Figure 1: Research area near Rostock (Germany) Figure 2: The UWSCS mounted on its framework

(Image: based on Landsat 4/5 TM satellite scene)

2 Methods

Bedforms, their evolution and migration is to be observed continuously over larger periods of

time (several months) on various defined monitoring areas of approx. 1 m² in several water

depths < 10 m close to the shores of Rostock (Mecklenburg-Western Pomerania, Germany,

comp. Fig. 1). The survey will be executed by means of a customized underwater stereophotogrammetric

camera system (comp. Fig. 2), based on the design by Korduan & Lämmel

(2005), providing the basis for 3D-data generation. This device will be deployed (comp. Fig. 3)

at various sites near Rostock-Warnemuende alongside ADCPinstruments gathering data of sea

state like wave-height, -direction and –length. Automatically, it will gather image pairs of the sea

floor in a default period, which will be processed to spatial data using remote-sensing software.

Elder examples for working with similar devices are given e.g. by Davies & Wilkinson (1977)

and Fryer (1983). Furthermore, laboratory experiments concerning the tolerable excavation

frequency of several bivalves such as mentioned Mya arenaria due to sediment transport as

well as the modification of pore water advection cells (comp. Fig. 4) will be examined.

1 Faculty of Interdisciplinary Research, Department Maritime Systems, University of Rostock, Justus-von_Liebig-Weg 6

LAG II, Rostock, 18057, Germany, (ulrich.floth@uni-rostock.de)


54 5th International Short Conference on Applied Coastal Research - SCACR 2011

3 Prospect

The UWSCS will be installed as an additional measuring device to the RADOST instrumentchain

(Regional Adaption Strategies For The German Baltic Sea Coast) which is a part of the

KLIMZUG-project (Regions Adapt to Climate Change) and shall gather sea state data along the

coast near Rostock-Warnemuende. In this term, the UWSCS will be deployed by scientific

divers who will periodically retrieve the device for data readout. The installation will presumably

happen in the end of January 2011.installationt will presumably happen in the end of January

2011.

Figure 3: Deployment of the UWSCS Figure 4: Pore-water advection (Precht et al. 2004)

4 References

Davies, A. G. ;Wilkinson R. H.(1977): The movement of noncohesive sediment by surface water

waves. Part I Literature Survey. Institute of Oceanographic Sciences, unpublished

manuscript.

Davies, A. G.; Frederiksen, N. A. & Wilkinson R. H. (1977): The movement of noncohesive

sediment by surface water waves. Part II Experimental Study. Institute of

Oceanographic Sciences, unublished manuscript.

Fryer, J. G. (1983): A simple system for photogrammetric mapping in shallow water. In: The

photogrammetric record, 11/62, 203-208.

Korduan, P.; Lämmel, D. (2005): Low cost-stereo UW-Kameramessystem,

http://www.auf.uni-rostock.de/gg/korduan/stereo.pdf.

Precht, E.; Franke, U.; Polerecky, L.; Huettel, M. (2004): Oxygen dynamics in permeable

sediments with wave driven pore water exchange. Limnology Oceanology, 49(3), 693-

705.

RADOST homepage: http://klimzug-radost.de/en/info.

Shum, K. T. (1992):Wave –induced advective transport below a rippled water-sediment

interface, Journal of geophysical research, 97, 789 - 808.


Book of Abstracts - Session 4: Coastal and Port Environments 55

Efficiency of artificial sandbanks in the mouth of the

Elbe estuary for damping the incoming tidal energy

Janina Marx 1 , Dagmar Much 2 , Jens Kappenberg 3 , Nino Ohle 4

1 The THESEUS Project

Coastal areas are among the most densely populated areas of the world. They play an important

role in terms of industry, agriculture, trade, tourism and settlement to mention some key

sectors. Today these areas already suffer from various problems like erosion, flood risk and

long-term habitat deterioration. Since the concentration of people in coastal areas is expected to

grow fast in the next decades and economies continue to develop the asset base of risk will

increase. Furthermore global climate change will raise the likelihood of extreme events, as well

as accelerate habitat decline. The combination of increasing economic and social values and

the impacts of climate change will lead to a growing pressure on coastal systems (HORSTMAN ET

AL., 2009).

The EU-Project THESEUS will investigate the applicability of innovative combined coastal mitigation

and adaption technologies. Besides technical aspects, social, economic and environmental

factors are included. The main aim is to deliver both a low-risk coast for human use and

healthy habitats for evolving coastal zones subject to multiple change factors (THESEUS, 2009).

2 The Elbe Estuary

The Elbe Estuary plays an important role for Northern Germany and functions for example as

an important federal waterway. The whole Elbe River has undergone several anthropogenic

changes since the 16th century like diking and river regulations. Additionally with natural changes

in hydrodynamics the measures caused an increase of the tidal energy and the tidal pumping

further upstream. As a result tidal range, sediment transport and siltation rate increased upstream.

In the framework of the THESEUS project the efficiency of artificial sandbanks in the

mouth of the Elbe Estuary for damping the incoming tidal energy is investigated (see also OHLE

ET AL., 2010).

3 Numerical Simulations

The efficiency and stability of the artificial sandbanks is analyzed by means of the 2-dimensional

hydrodynamic model TRIMNP. The model calculates the water level and current velocities on a

rectangular horizontal grid. To allow the investigation of the effects of the artificial sandbanks on

water level and currents in the inner estuary a spatial resolution of 50 m is used.

Figure 1 shows the bathymetry of the investigation area for today’s situation and the investigated

monitoring stations. Furthermore the shape and position of five artificial sandbanks in the

Elbe Estuary are indicated. The results of the numerical simulations of the reference situation

are calibrated and validated with data of several monitoring stations along the Elbe River. The

time domain of the simulations is the year 2006.

4 First Results

To show the effects of the different scenarios on water level and current velocities model results

are investigated at seven monitoring stations (Fig. 1). Summarized the first three sandbank

1 Helmholtz-Zentrum Geesthacht, Max-Planck-Strasse 1, 21502 Geesthacht, Janina.Marx@hzg.de

2 Hamburg Port Authority AöR, Neuer Wandrahm 4, 20457 Hamburg, Dagmar.Much@hpa.hamburg.de

3 Helmholtz-Zentrum Geesthacht, Max-Planck-Strasse 1, 21502 Geesthacht, Jens.Kappenberg@hzg.de

4 Hamburg Port Authority AöR, Neuer Wandrahm 4, 20457 Hamburg, Nino.Ohle@hpa.hamburg.de


56 5th International Short Conference on Applied Coastal Research - SCACR 2011

scenarios have nearly no influence on mean high and low water level at all gauging stations in

comparison to the reference scenario. They neither cause significant changes in current velocities

at the monitoring stations. Like analysis of the current vectors show, the flow field is only

modified in the immediate surrounding areas of the sandbanks. In a second step a fourth scenario

including all sandbanks of the first three scenarios is run. The results of the fourth scenario

show that the four artificial sandbanks together also cause no change in mean maximum high

water level, mean minimum low water level, mean flood current and mean ebb current velocities.

On the contrary scenario 5, an extended version of scenario 1, leads at five of seven monitoring

stations to an increase in mean minimum low water level of ~15 cm. Scenario 5 also

causes at all monitoring stations a decrease in mean maximum high water level of ~10 cm. In

comparison to the reference scenario the mean flood and ebb current velocities are also modified,

but values differ among the different monitoring stations.

Figure 1: Bathymetry and positions of investigated artificial sandbanks (Author’s design).

5 Acknowledgements

The support of the European Commission through FP7.2009-1, Contract 244104 - THESEUS

(“Innovative technologies for safer European coasts in a changing climate”), is gratefully

acknowledged.

6 Outlook

Further investigations will be done for the storm surge of November the 1st of the year 2006

with regard to the different sandbank scenarios. Furthermore the effectiveness of new sandbank

scenarios with larger sandbanks will be taken into account. In a final step the impacts of the

IPCC climate change scenario A1B will be investigated.

The overall results will contribute to the THESEUS aims to develop innovative risk mitigation

options and tools for coastal defense planning strategies.

7 References

Horstmann, E. M., Wijnberg, K. M. (2009): On the consequences of a long-term perspective for

coastal management. In: Ocean & Coastal Management, Vol. 52, No. 12, pp. 593-611.

Ohle, N., Much, D., Strotmann, T., Kappenberg, J., Weisse, R., Marx, J. (2010): THESEUS:

Investigations on Artificial Sandbanks in the Mouth of the Elbe Estuary for Mitigation of

Tidal Energy. Session D Poster on the Storm Surges Congress, Risk and Management

of current and future Storm Surges, University of Hamburg, Germany

THESEUS (2009): Protecting our coasts. http://www.theseusproject.eu.


Book of Abstracts - Session 4: Coastal and Port Environments 57

Estimation of wave attenuation over a Posidonia oceanica

meadow

Theoharris Koftis 1 and Panayotis Prinos 2

1 Introduction

The importance of coastal vegetation, such as seagrasses and salt marshes, regarding

biological and physical aspects has been well recognized; due to their capacity to alter their

environment and have been referred as “ecosystem engineers”. Additionally their ability to

attenuate wave energy and thus provide an environmental friendly shore protection has been

subject of several studies, in the field [Möller et al (1999), Brandley and Hauser (2009)] and in

the laboratory [Kobayashi et al (1993), Mendez et al (1999), Mendez and Losada (2004),

Stratigaki et al (2010)].

The degree of wave attenuation depends both on the plant characteristics (the seagrass

density, the canopy height, the stiffness of the plant and the bending of the shoots) and the

wave parameters (wave height, period and direction). In the present work, the data of large

scale experiments, conducted in the large scale wave flume of LIM/UPC for intermediate water

waves over artificial Posidonia oceanica meadow, are analysed. The purpose of the study is to

define an expression that relates the wave height decay with the meadow characteristics.

2 Experimental setup- analysis of results

The experiments are performed for regular and irregular waves over artificial P. oceanica

meadow, with different submergence ratios, hs/D equal to 0.32, 0.37, 0.42 and 0.50 (hs is the

canopy height and D the water depth) and seagrass densities (360 and 180 stems/m 2 ). Wave

height measurements are taken at several locations along the P. oceanica meadow. The wave

peak period, Tp, ranges between 2.0 s and 4.5 s, incident wave height, Hs, between 0.28 m and

0.40 m and the relative water depth, D/L, between 0.09 and 0.29 (L is the water wavelength).

In most of the above mentioned studies, the wave height decay for submerged vegetation is

assumed to be described either with an exponential function (1) or in the form of (2)

H

Kv � �exp( �kx

i )

H

K

v

o

H 1

� �

H 1�

� x

o

with Kv damping coefficient

H wave height [m]

Ho incident wave height [m]

ki decay coefficient

β coefficient

x distance along meadow [m]

1

Hydraulics Laboratory, Department of Civil Engineering, Aristotle University of Thessaloniki, 54124, Thessaloniki,

Greece, thkoftis@civil.auth.gr

2

Hydraulics Laboratory, Department of Civil Engineering, Aristotle University of Thessaloniki, 54124, Thessaloniki,

Greece, prinosp@civil.auth.gr

(1)

(2)


58 5th International Short Conference on Applied Coastal Research - SCACR 2011

The coefficients above are related to the wave and plant parameters. The study focuses on

defining a relationship for these coefficients, expressed as a function of the plant characteristics,

such as the seagrass density (stems/m 2 ) and the canopy submergence ratio hs/D. Figure 1

shows the wave height distribution over the seagrass meadow for plant density of 360

stems/m 2 , for several experimental runs, together with the plot of Equation (1) with different

values of the exponential decay coefficient ki, found in the above mentioned literature.

Figure 1: Wave height distribution along the seagrass meadow with 360 stems/m2

3 Acknowledgements

The experiments were conducted within the frame of Hydralab III 022441 (RII3) EU project by

V. Stratigaki and E. Manca and the supervision of the second author. The assistance of the

CIEM laboratory staff is gratefully acknowledged.The support of the European Commission

through FP7.2009-1, Contract 244104 - THESEUS (“Innovative technologies for safer European

coasts in a changing climate”), is also acknowledged.

4 References

Bradley, K.; Houser, C. (2009): Relative velocity of seagrass blades: Implications for wave

attenuation in low-energy environments. In: Journal of Geophysical Research, Vol. 114,

F01004, doi:10.1029/2007JF000951.

Kobayashi N.; Raichlen A.W.; Asano T. (1993): Wave Attenuation by Vegetation. In Journal of

Waterway Port Coastal and Ocean Engineering, Vol. 119, No. 1, pp. 30-48.

Dalrymple R.A.; Kirby J.T.; Hwang P.A. (1984): Wave Diffraction Due to Areas of Energy

Dissipation. In Journal of Waterway Port Coastal and Ocean Engineering, Vol. 110, No.

1, pp. 67-79.

Mendez, F. J.; Losada I.J; Losada M. A. (1999): Hydrodynamics induced by wind waves in a

vegetation field. In: Journal of Geophysical Research, Vol. 104, 18.383-18.396,

doi:10.1029/1999JC900119

Mendez F.J.; Losada I.J (2004): An empirical model to estimate the propagation of random

breaking and nonbreaking waves over vegetation fields. In: Coastal Engineering, Vol.

51, No. 2, pp. 103-118.

Möller I.; Spencer T.; French J. R.; Leggett D. J.; Dixon M. (1999): Wave Transformation Over

Salt Marshes: A Field and Numerical Modelling Study from North Norfolk, England. In:

Estuarine, Coastal and Shelf Science, Vol. 49, No. 3, pp. 411-426.

Stratigaki V.; Manca E.; Prinos P.; Losada I.; Lara J.; Sclavo M.; Caceres I.; Sanchez-Arcilla A. (2010):

Large scale experiments on wave propagation over Posidonia Oceanica. In: Journal of Hydraulic

Research, IAHR (accepted for publication).


Book of Abstracts - Session 4: Coastal and Port Environments 59

The effect of organism traits and tidal currents on wave

attenuation by submerged vegetation

Maike Paul 1 and Tjeerd Bouma 2

1 Introduction

It is widely recognized that submerged seagrass vegetation can have a significant impact on

wave attenuation. To correctly account for the effect of seagrass on wave attenuation in coastal

protection and management, it is important to understand which vegetation traits and

hydrodynamic parameters drive wave attenuation by vegetation (Teeter et al., 2001, Patil and

Singh, 2009).

This study investigates the impact of submergence ratio, shoot stiffness and density on wave

attenuation. Additionally, and to our knowledge for the first time, this study investigates how a

tidal current affects wave attenuation by seagrass. In the natural environment most seagrass

meadows are exposed to waves superimposed on a tidal flow and the effect of this underlying

current on wave attenuation by vegetation is not yet known.

2 Materials and Methods

Two mechanically realistic seagrass mimics with different bending behavior (cantilever vs. whiplike)

were developed and several meadows were produced to cover a wide range of natural

densities (500-8000 shoots/m 2 ) and leaf lengths (10-30 cm). Experiments were carried out

under controlled conditions in a racetrack wave flume with a straight working section of 10.8 m

and 0.6 m width with a constant water depth of 0.3 m. The flume is equipped with a conveyor

belt system and a wave paddle, which allows generating unidirectional flow, regular waves or a

combination of both. Wave heights were measured at the leading edge and at the end of the

meadow for at least 600 s per run. Additionally, a video camera was used to record seagrass

movement through the glass wall of the test section.

From the wave recordings, dissipated wave height ∆H per meter meadow was derived as:

∆H = (H1-H2)/x (1)

with ∆H dissipated wave height [-]

H1 wave height at leading edge of meadow [m]

H2 wave height at end of meadow [m]

x length of meadow [m]

The leaf area index (LAI = leaf length * leaf width * density, m 2 m -2 ) was calculated for each

meadow and used to compare the wave attenuating capacity, as the meadows varied in leaf

length as well as density. Plant movement was expressed in excursion of the leaf tip which was

derived from video recordings.

3 Results

An effect of plant stiffness on wave attenuation was apparent when comparing the results from

both materials. The attenuating effect of the stiff material was much higher for any given LAI

compared to the flexible mimics, unless LAI was negligibly low. However, the flexible mimic was

1

University of Southampton, Waterfront Campus, European Way, Southampton SO14 3ZH, United Kingdom,

maike.paul@soton.ac.uk

2

Netherlands Institute of Ecology, Centre for Estuarine and Marine Ecology, P.O. Box 140, 4400 AC Yerseke, The

Netherlands, T.Bouma@nioo.knaw.nl


60 5th International Short Conference on Applied Coastal Research - SCACR 2011

able to reach the same dissipated wave height at approx. four times the LAI of the stiff mimic

(Figure 1a).

a

∆H [cm/m]

1.4

1.2

1.0

0.8

0.6

0.4

0.2

0.0

0 1 2 3 4 5 6

leaf area index [-]

b

∆H [cm/m]

0.90

0.80

0.70

0.60

0.50

0.40

0.30

0.20

0.10

0.00

0 5 10 15

observed canopy height [cm]

c

∆H [cm/m]

0.70

0.65

0.60

0.55

0.50

0.45

0.40

0.35

0.30

0 10 20 30

observed canopy height [cm]

Figure 1: Dissipated wave height as a function of a) leaf area index under waves only and of

canopy height for b) stiff mimics and c) flexible mimics at 1000 shoots per m2. ● = stiff,

▲ = flexible, ■ = no seagrass, black symbols represent the wave only case and grey

symbols represent the combined wave and current case.

The presence of an underlying current reduced wave dissipation as well as the observed

canopy height at any given vegetation length. The canopy height reduction caused by bending

is, however, not the only process affecting wave attenuation, as wave dissipation rates are still

lower in the presence of a current when comparing meadows with a similar actual canopy

height (see examples in Figure 1b-c). Comparison of data from all runs shows that ∆H

increases linearly with shoot density for a given canopy height and this increase is more

pronounced in the absence of an underlying current.

4 Discussion and Conclusions

Results showed that stiffness and leaf area index determine wave attenuation. The leaf area

index combines the effect of leaf length and shoot density and therefore indicates that density

can compensate for lack of canopy height and vice versa with respect to wave attenuation.

Additionally, a higher LAI can lead to the same dissipation rate for a flexible plant than a stiff

plant at lower LAI, which suggests that different growth strategies can lead to the same effect

on wave attenuation.

The presence of an underlying current led to a reduction in wave attenuation for all meadows.

The current bent the leaves, leading to a primary tension within the blades which restricted plant

movement and hence wave dissipation. Reduced plant movement and wave dissipation were

present for both materials, suggesting that the current affects wave dissipation independent of

the vegetation’s bending behavior. Reduction of wave dissipation increased with increasing

shoot density which could not be fully explained with the data collected during this study.

However, the results clearly show that experiments which are carried out under waves only

overestimate the wave attenuating capacity of seagrass compared to most natural

environments where underlying currents are present in the form of tidal flow.

5 Acknowledgements

The authors kindly acknowledge the use of MatLab code for zero-crossing and wave reflection

provided by Dr U. Neumeier and Dr T. Baldock, respectively. The lab experiments were possible

thanks to a Peter Killworth Memorial Scholarship and the first author would like to thank Christel

and Dieter from the Stiftung zur Förderung Paulscher Promotionen for uncounted hours of

invaluable help during preparation and execution of the experiments.

6 References

Patil, S.; Singh, V. P. (2009): Hydrodynamics of Wave and Current Vegetation Interaction. In:

Journal of Hydrologic Engineering, Vol. 14, pp. 1320-1333; ISSN 1084-0699.

Teeter, A. M.; Johnson, B. H.; Berger, C.; Stelling, G.; Scheffner, N. W.; Garcia, M. H.;

Parchure, T. M. (2001): Hydrodynamic and sediment transport modelling with emphasis

on shallow-water, vegetated areas (lakes, reservoirs, estuaries and lagoons). In:

Hydobiologia, Vol. 444, pp. 1-23; ISSN 0018-8158.


Book of Abstracts - Session 4: Coastal and Port Environments 61

Dynamic analysis of gravity quay walls under seismic forces

Kubilay Cihan 1 , Yalçın Yüksel 1 , Seda Cora 1

1 Introduction

The stabilities of caisson quay walls against all forces act on their body are mostly provided by

the friction existed at the bottom of the caisson. During earthquakes, the lateral earth pressure

increases in the saturated backfill due to excess pore water pressures build up. This conditon

might cause liquefaction in the backfill soil. In the past eartquakes, some extensive damage

such as sliding and tilting of caisson walls due to liquefaction has been observed. Yuksel et al.,

(2003), investigated the effects of the Eastern Marmara Earthquake occurred on 17 August

1999 on marine structures and coastal areas. Their experience reflected to a new design code

which was based on performance design of marine structures (Aydinoglu et al., 2008)

The seismic displacement of the caissons can be evaluated by dynamic analyses or simplified

dynamic analyses based on the Newmark sliding block concept. The Newmark sliding block

method defines the yield acceleration as the amplitude of the block acceleration when the factor

of safety for sliding becomes 1.0, and evaluates the block displacement by double integration of

the ground acceleration, which exceeds the yield acceleration. Comprehensive results for the

dynamic behaviour of soil and caissons can be obtained from dynamic analyses. But various

input parameters which are difficult to obtain are needed for dynamic analyses.

To determine displacement of wall due to earthquake by using dynamics analyses with FEM or

FDM or using simplified dynamic analyses is very difficult because stability of quay walls under

seismic action is very complicated phenomenon. In this study, the dynamic behaviour caissons

were investigated by using FEM method , new Turkish design code for port structures based on

performance-based approach and Newmark method and results were compared. Numerical

analysis of dynamic response of caisson quay walls was carried out by using Plaxis V8.2

software that can calculate with FEM.

1.1 Performance-based design according to the RHA code

Recent design codes for caissons demand performance-based designs. These codes require

that the seismic performance of the walls be evaluated based on the permanent wall

displacement after an earthquake. The General Directorate for Construction of Railways,

Harbours and Airports (RHA) of Ministry of Transportation of Turkish Republic has prepared a

seismic code rest on a performance-based design philosophy.

In Table 1, performance-based design parameters according to the RHA code are shown.

Table 1: Minimum performance objectives for port structures (Aydınoğlu vd., 2008)

Structure

Class

Earthq. Level

(E1)

Earthq. Level

(E2)

Earthq. Level

(E3)

Special - MD CD

Nominal MD CD (ED)*

Simple CD (ED)* -

Unimportant (ED)* (CS)* -

*Implied objectives not requiring desing verication

MD is minimum damage performance level, CD is controlled damage level performance, ED is

extensive damage performance level, CS is state collapse. E1 is earthquake level that the

probability of exceedance of (E1) level earthquake in 50 years is 50%. E2 is earthquake level

1 Yildiz Technical University, Davutpaşa, İstanbul, Turkey, kcihan@yildiz.edu.tr


62 5th International Short Conference on Applied Coastal Research - SCACR 2011

that the probability of exceedance of (E2) level earthquake in 50 years is 10%. E3 is earthquake

level that the probability of exceedance of (E3) level earthquake in 50 years is 2%.

2 Results

Safety factors of caisson walls, which has same height (h) and different width (b), against sliding

are shown in Figure 2. Considered structure is not safe against the sliding. It is seen that safety

factors against sliding increases with increasing b. Increasing of b supplies a rising of resistance

force.

FS

1.20

1.00

0.80

0.60

0.40

0.20

0.00

0.4 0.5 0.6 0.7 0.8 0.9 1.0 1.1

Figure 2: Safety factor against the sliding

Permanent displacements obtained from numerical analysis and Newmark sliding block method

were compared. Permanent displacements obtained from FEM, Newmark sliding block method

and yield acceleration values for different caisson walls are summarized in Table 2.

Table 2: Permanent displacements obtained from FEM and Newmark sliding block method

b/h

3 References

Displacement

(m)

(Newmark)

�=0.5

b/h

Displacement

(m)

(FEM)

�=0.5

Yield acceleration

ay(g)

0.5 0.012 0.00257 0.08

0.6 0.008 0.00227 0.095

0.7 0.004 0.002 0.11

0.8 0.002 0.00192 0.125

0.9 0.0015 0.00185 0.13

1 0.001 0.0015 0.145

Aydinoglu, N. M., Ergin, A., Guler, I. , Yuksel, Y., Cevik, E. And alcıner, A., (2008), “ New

Turkish Seismic Design Code for Port Structures; A Performance-Based Approach”,

ICCE 2008 Ed. Lehfeldt, R. And Schuttrumpf, H., Hamburg.

Yuksel, Y, Alpar, B, Yalcıner, A,C, Cevik,E, Ozguven, O, Celikoglu, (2003), “ Effects of the

Marmara Earthquake on the Marine Structures and Coastal Areas”, ICE, Water and

Maritime Eng. Journal, 156:147-163.


Book of Abstracts - Session 4: Coastal and Port Environments 63

(Architectural) measures to control wave overtopping inside

harbours

Koen Van Doorslaer 1 , Julien De Rouck 1 and Stefaan Gysens 2

1 Introduction

Oostende, a city located in the middle of the Belgian coastline, contains the 2nd seaport of

Belgium. According to the Belgian coastal safety plan, the coastline has to be protected to a

storm with a return period of 1000 years. During this storm, waves of 5m can occur outside

Oostende harbour, and the still water level inside the harbour is predicted as TAW + 7.20m

(TAW + 0.00m = average low low water spring + 0.388m). The city centre is located almost 3m

below this water level (around mean high water level TAW + 4.50m), and is protected by the

quaywalls of the harbour. Their height (average TAW + 7.00m) is not sufficient when this

superstorm would occur. A research project was carried out to define the necessary measures

to control the situation and minimize the risk on flooding of the city centre. The outcome of this

study was to increase the freeboard by building a storm wall of 1.2m high at 15m away from the

quay wall. Small scale tests were carried out to investigate whether the presence of steps (with

the same height as the 1.2m high storm wall), benches or other architectural implementations

could be integrated as wave overtopping decreasing measure. This abstract shortly highlights

the different geometries tested, and the overtopping measured at 15m away from the quay wall.

2 Storm wall of 1.2m high at 15m behind the quay wall

The most common geometry in the harbor of Oostende is presented on Figure 1. The storm wall

protects the low-lying area behind it. Due to this wall, the overtopping discharge can be limited

to 1l/s/m averaged during a storm with return period R = 1000 years. During this storm, the still

water level (SWL) is situated on the quay, as shown in Figure 1.

Figure 1: Measurement of impact forces on and overtopping over the storm wall

3 Alternative geometries

Three large steps, each 5m wide and 0.4m high, can be implemented on the quay platform. The

same freeboard is obtained, and tourists can walk or sit on the steps.

Figure 2: Alternative geometry with large steps

These large steps can also be replaced by shorter steps in the middle of the 15m quay platform.

Again, the freeboard is kept the same.

1

Ghent University, Department of Civil Engineering, Technologiepark 904, 9052 Zwijnaarde, Belgium,

koen.vandoorslaer@ugent.be, julien.derouck@ugent.be

2

Ministry of the Flemish Community, Coastal Division, Vrijhavenstraat 3, 8400 Oostende, Belgium.

Stefaan.gysens@mow.vlaanderen.be


64 5th International Short Conference on Applied Coastal Research - SCACR 2011

Figure 3: Alternative geometry with small steps

Many variants have been tested in the 2D wave flume of Ghent University (L x W x H = 30m x

1m x 1.20m) at a Froude length scale 1/20: with and without walls, some kind of Stilling Wave

Basin (see Geeraerts et al, 2006), parapets (recurve walls, see Van Doorslaer et al, 2010), …

All these architectural measures can decrease the overtopping discharge over the original storm

wall at the end of the 15m platform.

4 Test results

The hydraulic boundary conditions inside the harbor of Oostende are used. A 5m high wave can

penetrate through the harbor entrance, but will be highly diffracted inside the harbor. The wave

reaching the investigated structures, are reduced to HS = 1.25m. The peak period however

doesn’t change (TP = 12s), creating waves with very low wave steepness (


Book of Abstracts - Session 5: Coastal Developments 65

Coastal protection of lowlands: are alternative strategies a

match to effects of climate change?

Hanz D. Niemeyer 1

1 Abstract

The expected changes in global climate and the consequently resulting acceleration of sea-level

rise require a thorough reevaluation of coastal protection strategies in many parts of the world.

This requirement yields also for the lowlands at the southern North Sea coast in Europe which

are protected by a line of dykes since about 1,000 years. The anticipation of an accelerated

sea-level rise due to changing climate has raised the question if this strategy of keeping the line

will still be appropriate or if alternatives should be taken seriously into consideration. This yields

the more since furthermore a number of secondary effects will lead to stronger loads on coastal

protection structures: increasing intensity of storms and consequently higher set-ups of storm

surges (WOTH ET AL. 2005) create as well larger water depths in front of coastal structures as

the delayed adaption of tidal flat levels to an

accelerating sea-level rise (MÜLLER ET AL. 2007). Since

wave heights and periods on flats are strongly depthcontrolled

(NIEMEYER 1983; NIEMEYER & KAISER 2001)

any increase of local water depth is accompanied by

corresponding higher wave loads on coastal

structures.

Some alternatives to line protection are well known

from the past: retreat, accommodation and moving the

protection line seaward (Fig. 1). In this paper

alternatives to the currently exercised coastal

protection strategy are discussed including the

background of historical experience with alternative

strategies like set-back of the protection line or

combined protection by separate structures (Fig. 1).

Strategies in the past have often been enforced by the

invincible powers of nature processes in respect of

responding human capabilities. E. g. in the period of

the post-glacial sea-level rise people did not have tools

to withstand the flooding of their living areas: retreat

was inevitable for survival. Since a period with

lowering sea levels after A. D. a resettlement of the

fertile coastal lowlands took place and protection

against flooding during storm surges was provided by

artificially erected dwelling mounds being already

reported by Plini after visiting Northern Germany in the

1st century. When the sea-level started to rise again

people heightened the dwelling mounds more than

once in order to create save havens again storm

surges, which in the end harbored complete

settlements including churches. Since 1,000 the

strategy changed to protection: The erection of dykes

targeted at keeping the whole area safe during storm

surges. Albeit repeatedly failing the local population in

the lowlands improved the structures and with it also

Figure 1: Basic strategic alternatives in

response to sea-level rise (based on

IPCC 1990)

1 Coastal Research Station of the Lower Saxony Water Management, Coastal Defence and Neatur Conservation

Agency, An der Mühle 5, 26548 Norderney/East Frisia, Germany, hanz-dieter.niemeyer@nlwkn-ny.niedersachsen.de


66 5th International Short Conference on Applied Coastal Research - SCACR 2011

the self-governing communities organizing coastal protection by establishing obligatory rules for

all land-owners (NIEMEYER ET AL. 1996). The basics of this strategy are currently still the same at

the lowlands at the Southern North Sea coast in the Netherlands, Germany and Denmark. The

knowledge of inevitable occurrence of climate change and accompanying effects endangering

the present coastal protection system has triggered a discussion on strategic alternatives which

until now has been limited on qualitative judgements in respect of most important expected

effects: physical processes and costs. In order to close that gap as a first step physical effects

to be expected due to presently known climate change scenarios are evaluated on a regional

scale also delivering a sound basis for afterward cost-benefit evaluations: A research project on

future storm surge levels and wave attack in the Ems-Dollard estuary due to expected climate

change scenarios and alternative strategies for the mainland coast has been designed and

approved. It has already started in 2009 and is funded in the framework of the KLIFF

programme by the Lower Saxon Ministry for Science and Culture. Its major aim is to evaluate

both the effect of climate change on existing coastal protection structures and the loads on

alternative structures and landscape due to alternative strategies. Basing on the available

scenarios on climate change downscaling to wind fields above the North Sea will take place

providing wind fields in a first step. Using these boundary conditions enables modelling of storm

surges and accompanying waves in a model chain up to the coastline and into anticipated

flooded areas. The model results provide realistic data about the loads on landscape and

protection structures. Also part of the project is a socio-economic study enabling the regional

stakeholders to participate and support the project with their experience.

2 References

Müller, J. M.; T. Zitman, M. Stive, H. D. Niemeyer (2007): Long-term Evolution of the Tidal Inlet

’Norderneyer Seegat’. in: J. McKee Smith (ed.): Proc. 30th Int. Conf. Coast. Engg. San

Diego/Ca., USA. New World Scientific, New Jersey.

Niemeyer, H. D. (1983): Über den Seegang an einer inselgeschützten Wattküste. BMFT-

Forschungsbericht MF 0203.

Niemeyer, H. D. (2010): Protection of Coastal Lowlands: Are Alternative Strategies a Match to

Effects of Climate Change. Proc. 17th IAHR-APD Conference Auckland/New Zealand.

Niemeyer, H. D., H. Eiben, H. Rhode (1996): History and Heritage of German Coastal

Engineering. in: N. Kraus: History and Heritage of Coastal Engineering. Am. Soc. Civ.

Engrs., Reston/Va., USA

Niemeyer, H. D. & R. Kaiser (2001): Design Wave Evaluation for Coastal Protection Structures

in the Wadden Sea. Proc. 4th Int. Symp. Ocean Wave Measurem. & Analysis San

Francisco/Ca., Am. Soc. Civ. Engrs., Reston/Va., USA

Woth E., K. H. v. Storch (2008): Klima im Wandel: Mögliche Zukünfte des Norddeutschen

Küstenklimas. Dithmarschen Landeskunde – Kultur – Natur, 1/2008


Book of Abstracts - Session 5: Coastal Developments 67

The integrated coastal observation and model system COSYNA

Kai Wirtz 1 and Friedhelm Schroeder 1

Shelf and coastal seas are in bi-directional ways connected to the well-being of human

societies. Beside large natural fluctuations, coastal seas are subject to direct or indirect

anthropogenic forcing. They, in turn, provide various relevant services to human societies.

Recurrent issues are safety of transportation, safety of the environment, coastal defence, or

morphology changes due to sediment transport. Coastal ecosystems generate valuable food

resources and mediate important regional and global biogeochemical fluxes.

Societies living at or near coasts therefore have various information needs. A basic prerequisite

to meet these demands is the capability to produce a coherent state description which, in turn,

requires a systematic integration of measurements and modelling. In light of the often large

uncertainties inherent to physical, geological, or biogeochemical models of coastal seas, such a

coherent state description hence defines a challenge for coastal observations which in the past

have often been of fragmented nature.

The Helmholtz Zentrum Geesthacht (HZG, formerly GKSS) has thus started the development of

the Coastal Observation System for Northern and Arctic Seas (COSYNA). In its first

implementation stage and in cooperation with members of the German Marine Research

Consortium (KDM), the Federal Maritime and Hydrographic Agency (BSH), and port authorities,

COSYNA integrates operationally working, innovative and cost effective platforms for measuring

relevant state variables across the German Bight.

The COSYNA mission to obtain a synoptic and effective description of the German Bight is in

this presentation illustrated by (i) an overview on system components which are successfully

installed or planned, (ii) a short example on how merging observational results from different

components can produce significant added values, and (iii) an example for a pre-operational

product based on innovative schemes for assimilating data into a coastal physical model.

(i) COSYNA as an observatory is built on a network of regular or time continuous in situ

observations, and optical as well as radar remote sensing. Its instrumental repertoire consists of

a common package of state-of-the-art sensors at fixed and mobile platforms. New developed

innovative sensors that enable the measurement of important chemical,/biological parameters

have been integrated into the system. Key physical, sedimentary, geochemical and biological

parameters are observed at high temporal resolution in the water column and at the upper and

lower boundary layers. Automated FerryBox systems operate on ships of opportunity and on

several piles in shallow water areas and at offshore platforms such as FINO-3. MERIS ocean

colour data are processed with renewed algorithms for coastal waters. HF and X-band radar

systems provide high-resolution measurements of waves, currents and near-coastal topography

changes. High-resolution physical and biological measurements in 3D derive from regular ship

transects using a SCANFISH. In near future, these modules will be extended by glider missions

and installation of benthic landers.

COSYNA triggers technological development in various fields of operational research (e.g.

automated quality control or error and regular statistical analyses) and defines system

integration as a central task. A web based platform and a virtual lab at the HZG facilitate userfriendly

sharing or retrieving of data and products.

(ii) Still on the data level, significant scientific benefit arises from the combination of diverse

measurement approaches. With an integration of observations which cover different dimensions

of the system (from 0D time-series, 1D vertical profiles, 2D surface maps, to quasi-3D transects)

we can identify dominant processes and their effects, which could hardly be assessed using a

single approach. This is shown at the system scale of the German Bight by an integration of

1 Institute of Coastal Research at the Helmholtz Zentrum Geesthacht


68 5th International Short Conference on Applied Coastal Research - SCACR 2011

data from mobile and fixed station FerryBoxes, remote sensing (MERIS) and 3D SCANFISH

transects. The joined analysis in this case reveals the physical pre-conditioning for relevant

biological events as it finds a strong link between moving front systems, related turbidity

changes and meso-scale variability in algal spring blooms. Another aim of COSYNA is the

response to

(iii) The aim of COSYNA, however, goes beyond addressing particular research or coastal

management questions. It should foster development in applied and operational oceanography

and should verify this capability by generating cost effective information products. One first

example for such a product, originating from a tight fusion of high-resolution observations and

modeling, is the operational now- to short-term forecast of the water circulation in the German

Bight. For this product, current measurements obtained from a distributed system of HF radar

stations are assimilated into a hydrodynamic model (GETM). Fast data processing and new

schemes of data assimilation substantially enhance model performance and reliability and, this

way, demonstrate how the serial melding of state-of-the-art components leads to an extension

of the observed area and a more coherent description of the coastal environment.

Already two years after its onset, COSYNA has advanced our capability to (technologically)

implement and (scientifically) use coastal and shelf sea observatories. With its integration of

distributed observing systems and their model based processing it has defined a new

infrastructure scale in environmental research. It will continue to stimulate a coherent

development of instrumentation, monitoring strategies and data assimilation techniques. These

objectives are consistent with ongoing European initiatives for operational observations (e.g.,

EMODNET, EMECO) and will contribute to information and infrastructure needs defined by

European legislation (e.g., Water Framework Directive). The presentation will conclude with

engineering, scientific, and also management challenges appearing at the edge of the first

COSYNA development phase.


Book of Abstracts - Session 5: Coastal Developments 69

Shoreline detection in gentle slope Mediterranean beach

Giorgio Manno 1 , Carlo Lo Re 1 and Giuseppe Ciraolo 1

1 Introduction

This paper present a method to estimate the shoreline position using remotely sensed images

and considering the effects due to the presence of waves and tides. The shoreline position

continually changes in time because of the dynamic nature of water levels at the coastal

boundary, such as waves and tides. The shoreline is defined as the intersection between low

sea tide and land surfaces and is traditionally mapped by means of aerial photographs. As a

matter of fact the shoreline position rough extracted from an aerial photograph is a wet/dry line

that describes the instantaneous land-water boundary at the time of imaging rather than a

‘‘normal’’ or ‘‘average’’ condition. To take into account the shoreline oscillations due to the wave

motion, the use of an “ordinary” sea storm, defined as one year return period storm, was

proposed.

2 Methodology

The methodology proposed is divided in two parts: hydraulic and geomorphologic study. The

hydraulic study includes several steps: waves and tides data collection, “ordinary” storm

identification, propagation from offshore to nearshore of the wave motion with a numerical

model, analysis of tides. Geomorphological study was complementary and useful to determine

the positioning errors. This part of the study concerned: to find and to acquire historical maps

and aerial photos, to georeference the images in a common projection system (UTM WGS84

33N), to overlay data collection (GIS) and to characterize the beach morphology with in situ

survey (topographic measurements).

To test the proposed method a study case in a sandy beach in western side of Sicily was

performed. This coastal zone is a plane having NW-SE principal direction; its altitude is slightly

decreasing from NE to SW. The beach is located in the south of Marsala town and extends for

approximately 3 km between Torre Tunna (northern headland: 37°45'32.26''N, 12°27'40.00''E)

and Torre Sibilliana (southern headland: 37°43'36.31''N, 12°28'11.23''E), in the beach there are

several morphotypes and dunes.

A diachronic analysis and a detailed topographic surveying were carried out on both emerged

and submerged parts of the of the studied beach. Geomorphological in situ data were compared

with maps and with georeferenced remote sensing images acquired in 1994, 2000 and 2006.

The Lido Signorino beach was divided into 25 transects (26 profiles) and the equipment used

for topographic measurements was a pair of receivers GPS Real Time Kinematic (RTK) and the

master station was located near Torre Sibilliana. Sections were obtained from an alignment

materialized with two long poles which were set at regular intervals in shoreline direction.

By analyzing the coastline morphology, the wind sector amplitude is 131° between 195° and

300°N clockwise, moreover the close island of Favignana (the Egadi archipelago) blinds the

northern part of the sector narrowing it to 105° (195°÷300°N).

To evaluate the “ordinary” storm an extreme wave statistics study was carried out using the

equivalent triangular storm method. Furthermore to validate the result from the previous

method, a standard Weibull statistical analysis was performed. The wave propagation in the

area near the studied beach was performed with the third generation SWAN spectral model

(Booij, et al. 1999). Once the offshore wave propagation motion was computed, the next step

was the estimation of the maximum beach run-up. To estimate the run-up the empirical formula

of Nielsen & Hanslow (1991) and the Boussinesq type of model were used. For each profiles

measured was calculated the respective run-up. The sea level fluctuation due to astronomical

1 Dipartimento di Ingegneria Civile Ambientale e Aerospaziale (DICA), Area Ingegneria Idraulica e Ambientale.

Università degli Studi di Palermo.Viale delle Scienze Ed 8, 90128 Palermo (Sicily - Italy).


70 5th International Short Conference on Applied Coastal Research - SCACR 2011

and meteorological influences cannot be neglected. The factor of main interest is the frequent

recurrence of this phenomenon together with storms. The increase of the sea level has a direct

effect on the shoreline position and an effect on waves breaking that are also linked with the

shoreline itself. To quantify the effect of tide oscillation on the shoreline, records of the close

Porto Empedocle tide gauge were used (37°17'11.20'' N, 13°31'37.30'' E).

3 Results

The results of the proposed methodology, applied in the case study, showed a strip width of

~30 m, related both to “ordinary” storm and tide oscillation. The aim of the method is to define

not a single line but a strip of beach. As a matter of fact this band is related to the beach slope

and to the dynamic nature of water levels, such as waves and tides.

Figure 1: The shoreline band linked to the ordinary storm run-up and tide. The total width is

~ 30 m

Methodology limits are strictly related to offshore buoy data quality and availability. Furthermore

the knowledge of maritime conditions during the remote sensing data acquisition is of primary

importance to thoroughly verify the shoreline positioning. This result suggests to use, in coastal

studies and in state property mapping, not a line representing the shoreline but a strip linked to

the “ordinary storm”. Such kind of strip, in which falls the instantaneous shoreline, belongs more

to the sea than to the land.

4 Acknowledgements

The authors would like to express their sincere acknowledgment to the Istituto Idrografico della

Marina, for supplying bathymetric data.

5 References

Baldock, T.E., Weir, F., Hughes, M.G., 2008. Morphodynamic evolution of a coastal lagoon

entrance during swash over-wash. Geomorphology, Vol. 95, No. 3-4,15, 398-411.

Boak, E.H., Turner, I.L., 2005. Shoreline definition and detection: a review. Journal of Coastal

Research, 18, 1-13.

Boccotti, P., (2000): Wave mechanics for ocean engineering. Elsevier Science, pp. 1-496.

Booij, N., Ris, R.C., and Holthuijsen, L.H., 1999. A third generation wave model for coastal

regions, part I: model description and validation. Journal of geophysical research, 104,

7649-7666.

Lo Re, C., Musumeci, R.E., Foti, E., 2008. A new shoreline boundary condition for a highly non

linear 1DH Boussinesq model for breaking waves . In proceedings of the 3rd SCACR -

International Short Conference on applied coastal Research, pp. 211-218. ISBN 978-88-

6093-058-3. Lecce, Italy.

Nielsen, P., Hanslow, D.J., 1991. Wave run-up distributions on natural beaches. Journal

Coastal Research, 7, pp. 1139-1152.


Book of Abstracts - Session 5: Coastal Developments 71

Re-examining the Dean profile for designing artificial beaches

in Dubai

Andrew Brown 1 and Jon Kemp 2

1 Introduction

When designing any artificial beach, it’s desirable to avoid (or minimise) future maintenance

commitments by arranging the initial beach profile so that it remains in dynamic equilibrium given

the incident wave climate and provides protection to the hinterland. It is usual to provide a

flat beach berm which will provide space for recreational usage and will also dissipate wave

energy in storm conditions thus reducing overtopping. The beach berm height is usually the

wave run-up height of the design wave and design water level.

The complicated nature of the surf zone makes empirically describing a beach profile extremely

difficult and equilibrium beach profile theory was developed to provide a theoretical beach profile

that can be used by engineers. It has proven useful as a reference plane for understanding

complex transport and morphological processes, for determining the stability of beaches, for the

design of artificial beaches and for determining fill amounts in re-nourishment projects. The

equilibrium beach profile can be defined as the cross-shore profile of steady shape that is

reached if exposed to constant forcing conditions for a sufficiently long time (Larson, 1991). A

dynamic equilibrium exists where the profile does not undergo a net change even though particles

are in motion.

The design beach slope has traditionally been estimated using Dean’s Equilibrium Profile (Dean

and Dalrymple, 2002). However, it has been observed at many beaches in Dubai where the

upper beach is much steeper than that ascribed by Dean’s profile predictor. Therefore, as a

result of the continued development of artificial beaches in Dubai, there is a requirement for a

equilbrium profile predictor for this region.

This paper therefore presents a new method for predicting the equilbrium beach profile, as well

as the creation of a new Hybrid profile predictor. The new Hybrid profile predictor has been

incorporated into a spreadsheet in order to streamline its application in the design of new stable

beaches.

2 Methodology

Beach profile data from along the Gulf coast of Dubai was collected and supplied by Dubai

Muncipality. A mean profile was calculated from historical beach profiles using HR Wallingford’s

BDAS (Beach Data Analysis System). This was then compared to the Dean profile at varying

shoreline water levels to determine Dean’s profile validity in the area. Statistical analysis (Root

Mean Square Error) was used to determine the best fitting shoreline datum. Other profile predictors

were then tested and a Hybrid profile predictor created (Figure 1).

1 HR Wallingford, Wallingford, Oxfordshire OX10 8BA, United Kingdom. A.brown@hrwallingford.co.uk

2 HR Wallingford, Wallingford, Oxfordshire OX10 8BA, United Kingdom. J.kemp@hrwallingford.co.uk


72 5th International Short Conference on Applied Coastal Research - SCACR 2011

Figure 1: Example plot of the Hybrid profile predictor

3 Conclusion

The research discovered that the Dean profile is valid for predicting the equilibrium beach profile

below MHLW in Dubai, but failed to represent the increased concavity of the upper beach slope.

The Hybrid profile predictor extends the profile landwards to HAT.

The Hybrid profile predictor is a simple predictor that can be applied to a range of engineering

situations, in particular the design of artifical beach slopes on the Gulf coast of Dubai

4 Acknowledgements

The authors are grateful for the support and guidance provided during the study by HR Wallingford

and the University of Plymouth and Dubai Muncipality. In particular Alan Brampton, Belen

Blanco Tim Chesher, David Finch, Katie Firman and Shunqi Pan

5 References

Dean, RG & Dalrymple, RA (2002): Coastal processes with engineering applicaions. Cambridge

University Press.

Larson, M (1991) Equilibrium profile of a beach with varying grain size. Coastal Sediments ’91

pp 557-571


Book of Abstracts - Session 5: Coastal Developments 73

Further developments in a new formulation of wave

transmission

Giuseppe Roberto Tomasicchio 1 , Felice D’Alesssandro 1 and Gianluca Tundo 1

1 Introduction

Wave transmission and overtopping are phenomena that allow a certain amount of wave energy

to pass through and over a low-crested breakwater (LCS). The remaining part of the wave

energy is dissipated by the wave breaking over the structure and seaward reflected. As the LCS

is commonly adopted in coastal protection interventions, the prediction of the amount of energy

transmitted behind the structure is a crucial point in design practice; in the past, the coastal

research has led to various formulae for wave transmission that are widely used in engineering

applications, but each with their own limitations.

Early studies on wave transmission coefficient, KT, were performed in Japan in 1960s (Iwasaki

and Numata 1969, Goda and Ippen 1963) and in 1970s (Numata 1975, Tanaka 1976). Since

the late 1980s, the number of papers/reports concerning the LCS performance greatly

increased. Many studies have proposed empirical formulae for the wave transmission

coefficient through regression analysis of the laboratory data from model tests conducted with

irregular waves (d’Angremond et al. 1996, van der Meer et al. 2005, Buccino and Calabrese

2007).

Recently, based on 851 laboratory observations from 14 different physical model investigations,

Goda and Ahrens (2008) provided a simple but consistent method to predict KT considering the

wave energy transmitted over and through a LCS.

In the present paper, a revised version of the formulation by Goda and Ahrens (2008) is

proposed after a deep calibration and verification against a large database derived from

physical model experiments. The new formulation provides coastal engineers with a more

verified tool for the preliminary design of a LCS.

2 Laboratory datasets for calibration

Existing data on wave transmission have been collected to obtain an extensive database, the

largest one in comparison with the studies available in literature. The adopted database

considers more than 3500 data of KT from 33 datasets concerning experiments on wave

transmission at LCS for various types of coastal structures in design conditions, such as

smooth, rubble-mound rock, tetrapod and accropode armour unit slopes.

3 Comparison of the prediction formulation with datasets

The formulation for KT prediction proposed by Goda and Arhens (2008) has been modified and

calibrated following an accurate estimation of the coefficients to be adopted.

Figure 1 shows the comparison between the observed and predicted KT from the full database.

Respect to Goda and Ahrens (2008), the application of the new formulation gives a better

agreement between observed and predicted KT in spite of a much larger number of data taken

into account. An improvement in the accuracy of KT prediction is evident for values of KT < 0.4;

this result overcomes the slight tendency of overestimation in the lower values of transmission

coefficient derived by using the formulation by Goda and Ahrens (2008) in its original version.

1 Engineering Department, University of Salento, via per Monteroni, 73100 Lecce (Italy),

roberto.tomasicchio@unisalento.it, felice.dalessandro@unisalento.it, gianlucatundo@libero.it


74 5th International Short Conference on Applied Coastal Research - SCACR 2011

Observed KT

1,0

0,9

0,8

0,7

0,6

0,5

0,4

0,3

0,2

0,1

0,0

0,0 0,1 0,2 0,3 0,4 0,5 0,6 0,7 0,8 0,9 1,0

Predicted K T

Figure 1: Comparison between observed and predicted transmission coefficient

4 References

Aquareef (2002)

UPC (2002)

Wang Perm. (2002)

Wang Imp. (2002)

Zanuttigh (2002)

UCA (2001)

Seabrook&Hall (1998)

Melito&Melby (2002)

Seelig Imp. (1980)

Seelig Perm. I (1980)

Seelig Perm. II (1980)

van der Meer (1988)

Dae‐Kah Imp. (1985)

Dae‐Kah tetr. (1985)

Daemen (1991)

DH 3374 (1998)

Powell&Allsop (1985)

Calabrese (2002)

Ahrens (1987)

HD‐M2090 (1985)

HD‐H2061 (1994)

DH‐H4087 (2002)

DH‐H1872 (1994)

DH‐H2014 (1994)

DH‐H1974 (1994)

TU Delft (1997)

DH‐1872‐3D (1994)

Allsop (1983)

Padova (2004)

Dae‐Mai‐Ohl (2001)

DH‐4171 (2003)

DH‐H525 (1990)

Kimura (2002)

Buccino, M., and Calabrese, M. (2007): Conceptual approach for prediction of wave

transmission at low-crested breakwaters. In: Journal of Waterway, Port, Coastal and

Ocean Engineering, ASCE, 133(3), 213-224.

d’Angremond, K.; van der Meer, J.W.; and de Jong, R.J. (1997): Wave transmission at lowcrested

breakwaters, in: Proceedings of the 25 th Int. Conference of Coastal Engineering,

Orlando, Florida, ASCE, 2418-2426.

Goda, Y., and Ippen, A.T. (1963): Theoretical and experimental investigation of wave energy

dissipators composed of wire mesh screens. In: M.I.T. Hydrodynamics Lab. Report n°

60, 66 pp.

Goda, Y., and Ahrens, J.P. (2008): New formulation of wave transmission over and through lowcrested

structures, in: Proceedings of the 31 st Int. Conf. of Coastal Engineering,

Hamburg, Germany, World Scientific, 3530-3541.

Ivasaki, T. and Numata, A. (1969): A study on wave transmission coefficient of permeable

breakwaters, in: Proceedings of 16 th Japanese Conference of Coastal Engineering,

JSCE, 329-334 (in Japanese).

Numata, A. (1975): Experimental study on wave attenuation by block mound breakwaters, in:

Proceedings of 22 nd Japanese Conference of Coastal Engineering, JSCE, 501-505 (in

Japanese).

Tanaka, N. (1976): Wave deformation and beach stabilization capacity of wide-crested

submerged breakwaters, in: Proceedings of 23 rd Japanese Conference of Coastal

Engineering, JSCE, 152-157 (in Japanese).

van der Meer, J.W.; Briganti, R.; Zanuttigh, B.; Wang, B. (2005): Wave transmission and

reflection at low-crested structures: design formulae, oblique wave attack and spectral

change. In: Coastal Engineering, (52) 915-929.


Book of Abstracts - Session 5: Coastal Developments 75

A numerical study for the stability analysis of articulated

concrete mattress for submarine pipeline protection

Maria Gabriella Gaeta 1 , Alberto Lamberti 1

1 Introduction and study motivation

Submarine pipelines are widespread used along coastlines for waste water draining or for

gas/fluid transportation from platforms at deep waters. Depending on the installation area,

pipelines are subjected to waves and currents. The solution to improve pipe stability is to cover

them with a resilient mattress or blanket. The most commonly installed ones are the bitumen

mattress and the articulated concrete mattress, which are objects of this study. The mattress

covers the pipe with a particular shape, named “omega”. This configuration gives a more

hydrodynamic shape to the mattress + pipe system, eventually reducing the wave loads on it.

Nevertheless, the authors found lack of scientific experience on the hydrodynamic processes

developing around these protected pipelines, motivating the purpose of this study to investigate

the wave-induced forces on the articulated concrete mattress.

In order to calibrate the numerical model, drag and lift forces on a single pipeline lying over the

seabed are preliminarily evaluated and compared with experimental and analytical results

described in literature. Then, different tests are performed varying hydraulic and geometric

conditions with the purpose to investigate the relation between drag and lift forces applied to the

protected pipeline.

2 Numerical set-up

A 2DV RANS numerical model is used to evaluate the forces on the mattress and on the pipe.

Model details can be found in Lin & Liu (1998) and Gaeta et al. (2009).

A numerical simulation evaluating the wave induced loads over a single unprotected pipeline is

performed in order to validate the model results: the calculated drag, inertia and lift coefficients

are compared with literature values by Sumer & Fredsöe (1997), achieving good agreement and

allowing the following considerations for the protected pipeline configuration.

Figure 1: Articulated concrete block mattress: left, the numerical reproduction.

The studied mattress is a flexible concrete cover composed by hexagonal cross sectional

blocks linked together in the two directions with a cable net (Figure 1, right). Figure 1 (left)

reproduces the numerical discretization for the mattress s30. Different wave climate conditions

are simulated to reproduce the most common scenarios of the Mediterranean Sea: regular and

irregular waves propagating in, deep waters and breaking solitary wave propagating in shallow

waters.

3 Preliminary results

The used numerical model allows obtaining detailed information on velocity, pressure and

turbulence field around the structure (Figure 2).

1 University of Bologna, DICAM Idraulica, viale Risorgimento 2, 40136 Bologna


76 5th International Short Conference on Applied Coastal Research - SCACR 2011

Figure 2: Snapshots of velocity field around the pipeline: solitary wave propagates from left to

right.

The horizontal and vertical forces are evaluated integrating the pressure obtained from the

simulations along each block contour and along the pipe diameter. As first analysis, these

values are compared with the expressions by Morison et al. (1950) where the forces are

dependent on the empirical factors CD, CM and CD equal to the drag, the added mass and the lift

coefficients respectively.

Therefore, their choice is essential during the analysis of the global stability of the protected or

not protected pipeline system. These coefficients depend on the Reynolds number Re, the

Keulegan-Carpenter number KC; the relative roughness and the relative trench depth. For a

supercritical flow (Re>>10 6 ) and ignoring the other dependent factors, the coefficients are

dependent only by KC. A comparison of the drag, inertia and lift coefficients obtained by the

numerical results is performed with the values CD0, CM0 and CL0 suggested by the DNV -Rules

(1981), valid for a unprotected pipe over the seabed, and supercritical flows with KC =10 - 70.

By comparing the time history of the horizontal and vertical forces from numerical results with

the analytical expressions by Morison et al. (1950) evaluated using the velocity and acceleration

fields in undisturbed position, the preliminary values for the coefficients are shown in Table 1.

Table 1: Preliminary value for CD, CM and CL for deep and shallow waters from numerical

analysis.

CD CM CL

Deep water 0.5 CD0 0.25CM0 0.5 CL0

Breaking wave 0.85 CD0 0.25 CM0 0.85 CL0

4 References

Det Norske Veritas (1981) Rules for submarine pipeline system, Oslo.

Gaeta, M.G., Lamberti, A., and Liu, P. L.-F. (2009) A two phase numerical model for

incompressible fluids: air influence in wave propagation and applications. Proc. 31st Int.

Conf. Coast. Eng., 1, 144-156.

Lin, P., and Liu, P. L.-F. (1998) A numerical study of breaking waves in the surf zone, J. Fluid

Mech., 359, 239-264.

Morison, J.R, O’Brien JP et al. (1950) The forces exerted by surface waves on piles. J. Petrol.

Technology, AIME, 189, 149-154.

Sumer, M. and Fredsöe, J. (1997) Hydrodynamics around Cylindrical Structures, Adv. Series on

Ocean Eng, Vol. 12.


Book of Abstracts - Session 5: Coastal Developments 77

Geosynthetic tubes as construction element for coastal

protection works – fundamental design aspects;

application possibilities and practical experience

Markus Wilke 1 and Hartmut Hangen 2

1 Introduction

The use of geosynthetic tubes as construction element for coastal structures is increasing. The

system has become more common during the last decade. However, there are still some

uncertainties regarding the possible applications in the marine environment and the adequate

design of such a structure. This might be due to the absence of a general design guideline and

the novelty of the system. Therefore still a need for research exists (e.g. Van Steeg and

Vastenburg, 2010). Although some design approaches have been developed (e.g., CUR 217,

2006).

The scope of this paper is to outline the general design basics of geosynthetic tubes for coastal

protection works and to further provide practical experience by executed projects in Latvia and

Italy.

2 Design of geosynthetic tubes

Regarding the design of geosynthetic tubes external as well as internal failure mechanisms

have to be taken into account. The external design focuses on the stability of the geotextile tube

as an almost monolithic element e.g. exposed to wave loads whereas the internal stability

analysis deals with the geotextile tube shell, the fill material and the interaction of both elements

[CUR 217].

One of the most dominating design factors is the ratio h/D of the filling height h and the nominal

diameter (diameter of a perfectly shaped circle, D) of the geosynthetic tube. This ratio

significantly influences the generated tensile forces in the geotextile tube shell (see Figure 1).

Figure 1: Theoretical circumferential tensile forces depending on filling ratio h/D for different tube

diameters in the dry (γ = 14 kN/m³)

3 Practical experience and executed projects

By means of some selected projects the construction experience and the application

possibilities are shown. The selected projects illustrate the versatile application possibilities of

1

HUESKER Synthetic GmbH, Fabrikstraße 13-15, 48712 Gescher, wilke@huesker.de

2

HUESKER Synthetic GmbH, Fabrikstraße 13-15, 48712 Gescher, hangen@huesker.de


78 5th International Short Conference on Applied Coastal Research - SCACR 2011

geosynthetic tubes for hydraulic structure maintenance, land reclamation and submerged

breakwater construction

Figure 2: Project Port Kuivizu, Latvia: Maintenance of a damaged mole

Figure 3: Project Port Salacgriva, Latvia: Geosynthetic tube bund for land reclamation and port

extension

4 References

CUR Bouw & Infra, Rijkswaterstaat Bouwdienst en Dienst Weg- en Waterbouwkunde, NGO

Nederlandse Geotextilorganisatie (2006). Ontwerpen met Geotextile Zandelementen.

CUR-publicatie 217, Stichting CUR, Gouda, The Netherlands. (In Dutch). ISBN 90-

3760-083-2

Van Steeg, P.; Vastenburg, E.W. (2010): Large Scale Physical Model Tests on the Stability of

Geotextile Tubes. Test report Deltares, Delft, The Netherlands.

Wave overtopping on dikes [Title: type size 14 pt, fat letters, left-aligned, line spacing 1.5,

spacing before 0 pt, spacing after 12 pt]


Book of Abstracts - Session 5: Coastal Developments 79

Wave overtopping resistance of grassed slopes in Viet Nam

Le Hai Trung 1 , Henk Jan Verhagen 2 and Jentsje van der Meer 3

1 Introduction

Recent researches including in situ tests show that dike slopes which are covered with grass

are able to suffer significant wave overtopping discharges (Van der Meer, 2009). It is revealed

that grassed land is a potential material in coastal protection, especially for developing

countries. The sea dike system in Viet Nam, which has been built for centuries, is being

upgraded and strengthened to deal with the increasingly severe attack from the sea. On the

landward grassed slope, concrete revetments and grassed slope within concrete beams are

applied popularly. In order to investigate the strength of the grassed slopes against wave

overtopping, different grassed slopes have been tested by mean of the Wave Overtopping

Simulator on site. Part of the research results are presented in this paper.

2 Wave Overtopping Simulator and destructive tests

The Wave Overtopping Simulator was first developed in the Netherlands by Van der Meer to

simulate the overtopping waves on the dike crest and then on the landward dike slope and to

study the behaviour of the stability of crest and landward slope (Van der Meer, 2006). The

Simulator works basically as a water container, is continuously filled with a certain and constant

discharge and is emptied at predefined moments, as calculated for a particular storm, see

Figure 1. With a total volume of 22 m 3 , a maximum average mean overtopping discharge of 100

l/s per m can be generated by the Simulator.

In three coastal provinces of Viet Nam, different grassed slopes such as Vetiver grass (Vetivera

Zizanioides), Bermuda grass (Cynodon Dactylon) and a mixture of Bermuda and Vetiver were

tested with the Simulator in year 2009 and 2010. In all the tests, the same wave boundary

condition was applied with a significant wave height of 1.5 m and a peak period of 6.0 s.

Depending on the strength of the grass slope the mean discharge was increased from small to

large: 10; 20; 40 ... and up to 100 l/s per m. Each of these values represents a simulated storm

lasting for 4 hours.

3 Maximum wave overtopping discharge on grass slopes

In Hai Phong, two year old Vetiver grass planted on poor clay showed a considerable resistance

against wave overtopping when the mean discharge was 100 l/s per m. A combination between

Bermuda grass and good clay could suffer a maximum discharge of 70 l/s per m in the second

destructive test in Nam Dinh. In Thai Binh, a mixture of Bermuda and young Vetiver on good

clay was able to withstand similar discharge in the first case, see Table 1. At these maximum

values, grass slopes were damaged severely and the dike stability could be threatened.

4 Damage formation

Profiles and photographs of the grassed dike slopes were recorded at different moments during

testing. By comparing these data, it is found that under attack of overtopping flows generated by

the Simulator damages could be formed at the transition positions including geometrical

transition (Le et al., 2010) and material transition.

1

Delft University of Technology, Faculty of Civil Engineering and Geosciences, Stevinweg 1, 2628 CN Delft, the

Netherlands, H.T.Le@tudelft.nl

2

Delft University of Technology, Faculty of Civil Engineering and Geosciences, Stevinweg 1, 2628 CN Delft, the

Netherlands, H.J.Verhagen@tudelft.nl

3

Van der Meer Consulting BV, P.O. Box 423, 8440 AK, Heerenveen, the Netherlands, jm@vandermeerconsulting.nl


80 5th International Short Conference on Applied Coastal Research - SCACR 2011

Table 1: Maximum wave overtopping discharge on different types of grassed dike slopes

Grass Max discharge Specification

(l/s per m) Grass age Soil quality Concrete beam

Vetiver > 100 2 year old sandy clay no

Bermuda 70 > 3 year old good clay no

Mixture > 100 6 months good clay yes

Figure 1: Water flow released from the Wave Overtopping Simulator on the grassed dike slope.

5 Acknowledgements

The project “Technical Assistance for Sea Dike Research” financed by the Government of the

Netherlands is acknowledged for funding to build the Wave Overtopping Simulator and to

perform all the destructive tests in Viet Nam. Tests were performed by the Faculty of Marine and

Coastal Engineering, Water Resources University, Ha Noi, Viet Nam.

6 References

Le, H.T., Van der Meer, J.W., Schiereck, G.J., Vu, M.C., Van der Meer, G., 2010. Wave

Overtopping Simulator tests in Viet Nam. ASCE, proc. ICCE 2010, Shanghai, China.

Van der Meer, J.W., Bernardini, P., Sniijders, W. and Regeling, E., 2006. The Wave

Overtopping Simulator. ASCE, proc. ICCE 2006, San Diego, US.

Van der Meer, J.W., Schrijver, R., Hardeman, B., van Hoven, A., Verheij, H. And Steendam,

G.J., 2009. Guidance on erosion resistance of inner slopes of dikes from three years of

testing with the Wave Overtopping Simulator. Proc. ICE, Breakwaters, Marine

Structures and Coastlines, Edinburgh, UK.


Book of Abstracts - Session 6: Modeling, Management 81

Methods to detect changepoints in water level time series –

application to the German Bight

Sönke Dangendorf 1 and Jürgen Jensen 1

1 Abstract

Water level time series are important for the assessment of coastal protection measures. They

represent long term changes as a main loading factor for the dimensioning of buildings. For the

issues of coastal engineering a large number of homogeneous water level time series is

indispensable for the adequate selection of design parameters of coastal protection measures.

Because of the extension of coastal areas and estuaries the homogeneity of time series is not

always given. As shown in Mügge and Jensen (1991) local anthropogenic influences can impact

or corrupt the statistical analysis of the data. To avoid inaccuracies when estimating design

parameters it is important to detect and eliminate inhomogeneities.

Generally, discontinuities in time series result from different possible causes. Abrupt

changepoints can be caused by local short term vertical land movements at the gauge or

building measures. Long term changes depend on long term vertical land movements of the

coastline, morphological processes or climatic changes. As shown in figure 1 the estimation of

linear trends in time series is only approvable if the target series is homogeneous in time. If

there is a changepoint the estimation of trend will be strongly effected. For this reason it is

impossible to differentiate between local anthropogenic and large-scale natural changes of

water level.

Figure 1: Consequences of anthropogenic induced changepoints for the estimation of linear

trends

In this study several detection techniques for abrupt changes are evaluated. The methods have

been established by different authors for detecting changepoints in climatic time series.

Because of the high level of variance and natural variability in water level time series in the

German Bight it is not possible to assign these methods without extensive analysis.

1 Research Institute for Water and Environment, Department of Hydraulic Engineering, University of Siegen, Paul-

Bonatz-Str. 9-11, 57076 Siegen, Germany, soenke.dangendorf@uni-siegen.de


82 5th International Conference on Applied Coastal Research - SCACR 2011

The adaptability of the method was tested with more than 50.000 synthetic water level time

series. For the generation of synthetic time series with a length of 100 values Monte-Carlo-

Simulations were accomplished. With Monte-Carlo-Simulations it was possible to generate

normally distributed water level time series. These time series were combined with defined

trends and artificial steps (different sizes) at selected positions to produce time series with

statistical properties similar to those are observed in the annual mean water levels.

The evaluation of these synthetic time series showed that the methods - especially in

combination with some amplifications - are reliable to detect changepoints in water level time

series of the German Bight. Using the example of the building measures in the Meldorf Bight in

the 1970s, different applications of the Standard Normal Homogeneity Test (SNHT) - as the

best of the five evaluated methods with its own features - will be introduced. By incorporating

homogeneous and high correlated reference time series (Cuxhaven, Heligoland) it is possible to

detect anthropogenic changes with its step size as shown in figure 2. By building a new series

(D) from the differences of reference (Z1) and target (Z2) series variability, trends and

periodicity of the target series are reduced and the power of the test statistic is maximized. With

the detected changepoints a homogenization of the target series is possible. The

homogenization can make a contribution to a better quality of water level time series in the

German Bight and finally to the selection of design parameters.

Figure 2: Application of SNHT to water level time series by using the differences (middle) of

homogeneous reference (Cuxhaven, top) and target series (Büsum, top). Changepoint

is located where the maximum of the SNHT statistics occurs (bottom)

2 References

Mügge, H.E. and Jensen, J. (1991): Investigations of the Gauge Site of Büsum, Deutsche

Gewässerkundliche Mitteilungen, Vol. 35, No. 1, pp. 13-21, ISSN 0012-0235


Book of Abstracts - Session 6: Modeling, Management 83

The coastDat data set and its potential for coastal and offshore

applications

Elke M. I. Meyer 1 , Ralf Weisse 1 , Heinz Günther 1 , Ulrich Callies 1 , Hans von Storch 1 , Frauke

Feser 1 , Katja Woth 1 and Iris Grabemann 1

The coastDat data set is a compilation of coastal analyses and scenarios for the future from

various sources. It contains no direct measurements but results from numerical models that

have been driven either by observed data in order to achieve the best possible representation of

observed past conditions or by climate change scenarios for the near future. In contrast to direct

measurements which are often rare and incomplete coastDat offers a unique combination of

consistent atmospheric, oceanic, sea state and other parameters at high spatial and temporal

resolution, even for places and variables for which no measurements have been made. In

addition, coastal scenarios for the near-future are available complementing the numerical

analyses of past conditions.

The backbones of coastDat are regional wind, wave and storm surge hindcast and scenarios

mainly for the North Sea and the Baltic Sea. Furthermore, hindcast simulations are available for

temperature, salinity, water level and currents for the North Sea for the last 60 years.

CoastDat data are derived as follows. A regional atmosphere model with focus on Europe and

adjacent seas is driven by the global NCEP/NCAR re-analysis in combination with a simple data

assimilation algorithm (Feser et al. 2001) in order to obtain a better representation of nearsurface

marine wind fields (von Storch et al. 2000). From this regional simulation, near-surface

marine wind-fields and other parameters are stored hourly. They are then used subsequently to

drive storm surge and wind wave models for the North Sea. In this way a high-resolution and

consistent meteo-marine hindcast for the past 60 years has been generated. Here consistency

refers to the fact that the output fields from the different models (wind, waves and storm surges)

are in physical agreement, a fact that is frequently ignored e.g., when waves and surges from

different sources are analysed jointly.

We will discuss the methodology to derive these data, their quality and limitations in comparison

with observations. Long-term changes in the temperature, wind, wave and storm surge climate

will be discussed and potential future changes will be assessed. We will conclude with a

number of coastal and offshore applications of coastDat demonstrating some of the potentials of

the data set in hazard assessment. For example Figure 1 shows an exercise from an oil risk

assessment. Here the coastDat data set has been used to force an oil spill model. For any

particular source region (characterized for instance by dense ship traffic), hypothetical accidents

were assumed to occur every 28 hours over the 1958-2002 period. The latter provides a rather

reasonable sample of the different possible marine weather situations which in turn allows for

the estimation of different statistics that characterize the risk and sensitivity of any target region

that might potentially be influenced by the accidents. As an example, Figure 1 shows one result

of such an analysis for the island of Helgoland. The analysis may be further refined taking into

account for example the facts that the probability of an accident might be conditioned upon the

weather situation, that different oil fighting strategies may be applied whose efficiency in turn

may depend on the weather or that the vulnerability of several target regions may vary.

1 Institute for Coastal Research, Helmholtz-Zentrum Geesthacht, Centre for Materials and Coastal Research GmbH,

Max-Planck-Str. 1, 21502 Geesthacht, Germany, elke.meyer@hzg.de


84 5th International Conference on Applied Coastal Research - SCACR 2011

Figure 1: Use of coastDat in oil risk modeling. Left: Colored boxes show hypothetical accident

regions within a traffic separation scheme. Numbered boxes are target regions for

which impact statistics have been computed. Right: Example of impact statistics for

target region 14 (Helgoland). Shown are the frequency distributions of travel times that

are needed for the pollution caused by an accident to reach region 14. Color codes

match the source regions (left). Region 14 is hit in 65%, 50%, 43% and 37% of

accidents depending on source region (right panel from top).

1 References

Feser, F., R. Weisse, and H. von Storch, 2001: Multi-decadal atmospheric modeling for Europe

yields multi-purpose data. Eos Transactions, 82, pp. 305, 310.

von Storch, H., H. Langenberg, and F. Feser, 2000: A spectral nudging technique for dynamical

downscaling purposes. Mon. Wea. Rev., 128, 3664-3673.

Weisse, R., von Storch, H., Callies, U., Chrastansky, A., Feser, F., Grabemann, I., Günther, H.,

Pluess, A., Stoye, T., Tellkamp, J., Winterfeldt, J. & Woth, K. (2009), "Regional

Meteorological-Marine Reanalyses and Climate Change Projections: Results for

Northern Europe and Potential for Coastal and Offshore Applications", Bulletin of the

American Meteorological Society. 45 BEACON ST, BOSTON, MA 02108-3693 USA,

JUN, 2009. Vol. 90(6), pp. 849-860. AMER METEOROLOGICAL SOC.


Book of Abstracts - Session 6: Modeling, Management 85

Wave impact on a seawall with a deck and on a baffle in front of

seawall

Nor Aida Zuraimi Md Noar 1 and Martin Greenhow 2

1 Introduction

Given the uncertainty in wave climate and water aeration in extreme conditions, and the

sensitivity of maximum impact pressures on the exact alignment of the impacting wave surface

with the seawall, results from measurements/calculations are highly variable. Thus Cooker and

Peregrine (1995) proposed using the pressure impulse P(x,y) that is the time integral of the

pressure over the duration of the impact. This results in a simplified, but much more stable,

model of wave impact on the coastal structures. This paper continues the work of Greenhow

(2006) who extended Cooker’s model to breakwaters with a ditch or berm by using

eigenfunction expansions of the pressure impulse. That paper will be reviewed and extended

before considering the following simplified model for impact on a wall with: i) a deck extending

from the top of vertical seawall, ii) a baffle in front of the vertical seawall.

2 Pressure impulse impulse on a seawall with a deck

We present the pressure-impulse calculations for a wave impact on a vertical seawall with a

rigid horizontal deck of finite extension. The impacting wave is assumed to be vertical, with a

constant horizontal velocity in the impact region 0 < x < µ. The fluid is assumed to be

incompressible, inviscid and irrotational giving Laplace’s equation for the pressure impulse

throughout the fluid, together with Dirichlet or Neumann boundary conditions. The problem is

non-dimensionalised using the water density, � and depth, H and impact velocity,U0. Two

regions, below the deck and below the free surface are written as appropriate eigenfunction

expansions (including secular terms) and P and its x-derivative are matched by collocation at

x=b1 i.e. a vertical line at the end of the deck. This problem has a square root singularity where

the end of the deck meets the free surface. To circumvent this, we use a collocation method

with no collocation point at the singularity. Figure 1 shows the distribution of pressure impulse

for different lengths of deck, the shorter deck being comparable to the no-deck solution of

Cooker and Peregrine (1995) except near the deck where the pressure impulse is substantially

higher.

deck, b1=0.1

0

-0.1

-0.2

-0.3

-0.4

-0.5

-0.6

-0.7

-0.8

-0.9

free surface

-1

0 0.5 1 1.5 2

0.1

0.09

0.08

0.07

0.06

0.05

0.04

0.03

0.02

0.01

deck, b1=0.5

0

Figure 1: Pressure impulse contours on the wall for µ=0.1. The maximum pressure impulse for

b1 = 0.1 and b1 = 0.5 are approximately 0.102 � H and 0.204 � H respectively.

1 Brunel University, Department of Mathematical Sciences, John Crank Building, Uxbridge, Middlesex,UB8 3PH, United

Kingdom, 1 mapgnab@brunel.ac.uk and 2 mastmmg@brunel.ac.uk

-0.1

-0.2

-0.3

-0.4

-0.5

-0.6

-0.7

-0.8

-0.9

-1

0 0.5 1 1.5 2

U 0

free surface

U 0

0.2

0.18

0.16

0.14

0.12

0.1

0.08

0.06

0.04

0.02


86 5th International Conference on Applied Coastal Research - SCACR 2011

Figure 2: Pressure impulse on the wall for varying µ with deck b1 = 0.1

It is found that the pressure impulse increases with deck length, and with the size of the impact

region µ (as in Cooker and Peregrine (1995) for the no-deck case). Overall impulses and

moments on the wall and deck will be presented, together with a simplified model of

overtopping.

3 Pressure impulse impulse on a baffle in front of seawall

Now we consider the pressure impulse acting on a vertical baffle in front of the seawall at x=b1

with depth of penetration Hb. The formulation is similar to the deck problem, but the seawall and

matching is achieved by a combination of Fourier and collocation methods that have been

shown to be stable and converge. Figure 2 shows the pressure impulse contours.

0

-0.1

-0.2

-0.3

-0.4

-0.5

-0.6

-0.7

-0.8

-0.9

-0.2

-0.4

-0.6

-0.8

-1.2

Hb=0.5, mu=0.5

-1

-1 -0.5 0 0.5 1 1.5 2

0.25

0.2

0.15

0.1

0.05

0

-0.1

-0.2

-0.3

-0.4

-0.5

-0.6

-0.7

-0.8

-0.9

Hb=0.8, mu=0.5

-1

-1 -0.5 0 0.5 1 1.5 2

Figure 3: Pressure impulse contours on the wall for µ=0.5. The maximum pressure impulse for

H = 0.5 and H = 0.8 respectively are approximately 0.255 � H and 0.280 � H .

From the figure above we can see that the pressure impulse on the front/rear of the baffle

increases/decreases when the length of baffle increases. Overall impulses and moments on the

wall and baffle will be presented, including cases where large pressure impulse on the rear of

the baffle gives it an overall impulse in the seaward direction.

4 References

Pressure Impulse on the Wall

0

0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8

-1

� � 0.

1

� � 0.

5

� � 1.

0

Greenhow, M (2006) ‘Wave impact on seawalls of various geometries.’Proc. 1 st Int. Conf.

Coastlab, 517-524

Peregrine, D.H (2003) ‘Water-wave impact on walls.’ Annu. Rev.Fluid Mechanics,35:23-43

Cooker, MJ., Peregrine, D.H (1995) ‘Pressure-impulse theory for liquid impact problems.’

J. Fluid Mech. 297:193-214

U 0

0.25

0.2

0.15

0.1

0.05

U 0


Book of Abstracts - Session 6: Modeling, Management 87

Mappping

thee

tempor ral and sspatial

di istributio on of expperiment

tal

imppact

induuced

pres ssures aat

vertica al seawal lls: a novvel

method

Dimittris

Stagonass

1 , Gerald Mϋ ϋller 1 , Williamm

Batten 1 an nd Davide Ma

1

Curreent

knowledgge

on wave pressures aat

vertical walls w mainly comes fromm

2D experim mental

studiees.

Nevertheeless,

maxim mum impactt

pressures are commonly

assumedd

to occur in the

middlle

of the struucture

and hence h an arrray

of press sure transduc cers is usedd

to provide single

point records of the vertical pressure diistribution.

Accordingly,

A

it comes ass

no surprise

that

almosst

nothing iss

known regarding

the hhorizontal,

te emporal and spatial, disttribution

of impact

presssures

on verttical

seawalls s and breakwwaters.

Throuugh

the trans

the hhorizontal

an

seawwall

is made

100cmm

tradit

distrib

The c

struct

comb

2 sfer of techn nology from other fields of research, the simultanneous

mapp ping of

nd vertical distribution

off

impact ind duced pressu ures at the face of a vertical

possible he ere for the ffirst

time. Both

the size e of the mappping

area (here,

) and thee

measuring resolution ( (here, 392 sensing s poin nts) cannot be achieved d with

ional pressuure

transducers.

Resultss

presented reveal an uneven

verticcal

and horizontal

bution with mmaximum

pr ressures occcurring

in are eas of the seawall s wherre

least expe ected.

cushioning eeffect

of the entrapped e air

cavity and pressures in nduced at thee

lower part of the

ture due too

the large accelerationn

of the tro ough are do ocumented hhere

through

the

bination of the

proposed technology t wwith

high spe eed video.

The ppurpose

of thhe

current work w is to intrroduce

the coastal c engin neering commmunity

to this

new

technnology.

Suppport

is provid ded by prelimminary

result ts of a 2D physical

studyy

including spatial s

and ttemporal

reccords

of the impact inducced

pressure e distribution n at the frontt

face of a vertical

wall.

2

All exxperiments

reeported

here e were conduucted

in the shallow s wate er wave flumee

of the Univ versity

of Soouthampton

hhydraulics

laboratory.

A 11:20,

imperm meable slope e was placedd

at one end of the

flumee

followed byy

a vertical seawall

madee

out of Pers spex. A cons stant water ddepth

of 20.5 5cm in

front of the wavve

paddle and a 5.7cm at the vicin nity of the seawall waas

chosen for f all

meassurements.

1 Civil

Introducction

Experimmental

set-up

Figure 1:

Pictures of the e pressure paads

used at the e seawall face e

agagna 1

Engineering Deepartment,

Unive ersity of Southaampton,

Highfiel ld, Southampton n, SO17 1BJ, UUK,

phone:

+44(00)2380592442,

fax: +44(0)2380677519,

e-mail:

ds3e10@soto on.ac.uk, G.Muller@soton.ac.uuk,

W.Baatten@soton.acc.uk,

gm7@soto on.ac.uk, dgw1006@soton.ac.uk

k


88 5th International Conference on Applied Coastal Research - SCACR 2011

For a range of incoming wave w conditioons,

the tem mporal and spatial distrribution

of i

presssures

was mapped

with a sampling rrate

of 4 kHz z, over an are ea of 100cmm

of thee

wall and laater

over a similar s in sizee

area but along a the wall’s

height. T

used for the current

tests are

illustratedd

in figure 1.

A detailed d description

method

will be inccluded

in the e final paper.

2 mpact

along the length

The pressure e pads

n of the proposed

3

Figurre

2, illustrattes

subsequent

impacts at the verti ical seawall for the samme

incoming wave

condiitions;

H = 66cm

T = 3.4 4sec. Video frames (600 0 fps) of the e impact are e presented at the

upper

part of thee

image alon ng with the ccorrespondin

ng records fr rom the presssure

pads; lower

imagee

part.

Impulsive

pressures

are originally

recordded

from the pad located d in the midddle

of the se eawall

and tthey

accordinngly

propaga ate towards tthe

flume’s ri ight side wall;

from left too

right in figu ures 2.

Althoough

an unevven

longitudinal

pressuree

distribution n is not surp prising, it is wworth

noticing

that

maximmum

impact pressures are a recorded near the side

wall and not

at the midddle

of the se eawall

face, as very commmonly

assu umed. Thesee

maximum pressures p wo ould have beeen

ignored by an

arrayy

of transduccers

placed at the midddle

of the model m structu ure. The lattter

also ent tails a

temporal

shift andd

a significan ntly larger maagnitude

for the wave ind duced force.

4

A novvel

measurin

(tempporal

and sp

possiible

for the fi

large as 100cm 2 ng method fo or wave presssures

is pre esented here e. The high re resolution dynamic

atial) and ma apping of waave

impacts at a vertical breakwater / seawall is made

irst time. Sim multaneous measurements

can be provided p for sstructure

are eas as

. The propose ed techniquee

is robust an nd easy to se et-up and usee.

5

Resultss

Figure 2:

Conclussions

Referennces

Above, video frames of a wwave

plunging

at the seaw wall and beloww

the corresponding

pressure map ps. Only the mmeasuring

area a is represented

in the mapps

and not the whole

wall; T = 3.4sec

and H = 6ccm.

Archeetti,

L. Martinnelli,

P. Friga aard, A. Lammberti

(2000) ): Horizontal coherence oof

wave forc ces on

vertical waall

breakwate ers, Proc. Off

the 27th ICCE,

pp 20

Oumeeraci,

H., Koortenhaus,

A., A (1994): AAnalysis

of dy ynamic response

of caissson

breakw waters.

Special isssue

on vertic cal breakwatters.

Coastal l Engineering g Vol. 22, Noo.1–2,

pp.159 9–183

Schuttrumpf

A., AA.

Kortenhau us, H. Oumeeraci

and L. Martinelli, (2 2000): Presssure

distribut tion at

the front fface

and the e bottom of a vertical bre eakwater in multidirectioonal

seas, Pr roc. of

the 27th ICCE,

pp. 2072–2085,

Syydney,

Australia.


Book of Abstracts - Session 6: Modeling, Management 89

First results of large scale model tests on the stability of

interlocked placed block revetments

Fabian Gier 1 , Holger Schüttrumpf 1 , Jens Mönnich 2 , Matthias Kudella 3

1 Introduction

Revetments are usually applied in coastal areas along estuaries and coasts in order to protect

the shores against waves and currents. Therefore, the loading of a revetment depends on the

wave and current induced forces, while the strength depends on the stability of the revetment

against wave and current attack. Various types of revetments are applied in coastal areas which

can be divided in two general systems:

� Riprap revetments

� Placed block revetments

The focus of the present study was set on the stability of interlocked block revetments which

belong to the placed block revetments. Interlocked block revetments are expected to have a

higher stability than loose placed block revetments due to the connections between the

individual stones. The Verkalit®-block, developed by BERDING BETON GmbH, is an

interlocked block with a special key and slot system (Figure 1). The Verkalit®-block was tested

in the Large Wave Flume in Hannover to investigate the additional stability compared to

traditional placed blocks without interlocking.

Figure 1: Verkalit®-revetment block with key and slot system

A number of design approaches for placed block revetments without interlocking can be found

in literature (Bezuijen et al., 1990; Bezuijen and Breteler, 1996; Pilarczyk, 2001). Until now, the

additional effect of interlocking, like the key and slot system, has never been taken into account

in design approaches. Therefore, physical model test were required and performed in the Large

Wave Flume in Hannover. Objective of these tests was to gain a better knowledge about the

behaviour of interlocking stones, especially the benefit on stability due to the key and slot

system.

2 Setup of the Physical model tests

The Verkalit®-revetment block was tested in the Large Wave Flume in Hannover (length 307 m,

depth 7 m, width 5 m). The dimension of the Large Wave Flume allows physical model tests in a

1:1 scale. Thus, scale effects can be avoided.

All model tests in the Large Wave Flume were performed for a 1:3 seaward slope divided in two

parts. A traditional revetment block was tested on the left hand side, while the Verkalit®-

1

Institute of Hydraulic Engineering and Water Resources Management, RWTH Aachen, Kreuzherrenstraße 7, 52056

Aachen, Germany, gier@iww.rwth-aachen.de, schuettrumpf@iww.rwth-aachen.de

2

BERDING BETON GmbH, moennich@berdingbeton.de

3 Technical University of Hannover, Large Wave Flume, Hannover, e-mail: kudella@fzk-nth.de


90 5th International Conference on Applied Coastal Research - SCACR 2011

revetment block was tested on the right hand side. Thus, a direct comparison of the stability of

the different systems was possible. To ensure a direct comparison, the stone weight and the

opening ratio were kept almost identical. The revetment was constructed with a sand core, a

geotextile and a grain filter according to present technical standards.

The test programme included regular waves, JONSWAP wave-spectra and longterm tests. It is

based upon the manual of “Criteria voor toepassing van bekledingen op waterkeringen” of

Wittven and Bos and Deltares (2010) and shows a step by step increase of the incoming load.

3 First Results

Tests were performed with increasing wave load during the first project phase. At a significant

wave height HS = 0.8 m and a peak period of TP = 3.58 s the traditional revetment failed (Figure

2, middle picture). Enourmous settlements (up to 5 cm) and block uplifts (up to 9 cm) occured.

To avoid further damages, tests were stopped and the traditional revetment was replaced by a

Verkalit®-revetment.

In contrast, neither obvious settlements nor uplifts could be observed or measured for the

Verkalit®-revetment, consisting out of interlocked block (Figure 2, left picture). Therefore, it can

be concluded that the interlocked revetment is more stable than the traditional revetment.

Figure 2: left: Verkalit®-revetment block; middle: Ordinary revetment block; left: picture:

enormous settlements and uplifts in the area with the ordinary revetment block

The revetment out of traditional blocks was replaced by the Verkalit®- block in order to continue

the test progamme. Despite of operating the wave generator at its power limit, it was impossible

to load the Verkalit®-revetment to the point of failure. Nevertheless to have an idea about the

stability of Verkalit®-revetment blocks, additional pull out tests were performed by measuring

the required force to lift a single block out of the revetment. The measured force represents a

reference value for the necessary uplift force on a single block to bring the cover layer to failure.

Further results will be described in more detail in the final paper.

4 References

Bezuijen, A.; Klein Breteler, M.; Burger, A. M. (1990): Placed block revetments. In: Coastal

protection : proceedings of the Short Course on Coastal Protection, Delft University of

Technology, 30 June - 1 July 1990 / Pilarczyk, Krystian W. Rotterdam [u.a.]: Balkema,

pp. 289-326. - ISBN 90-6191-127-3

Bezuijen, A. u. Breteler, M. K. (1996): Design formulas for block revetments. In: Journal of

Waterway Port Coastal and Ocean Engineering-Asce, Vol. 122, No. 6, pp. 281-287.-

ISSN 0733-950X

Pilarczyk, K. W. (2001): Dikes and revetments: Design, maintenance and safety assessment,

Rotterdam, Balkema 1998. - ISBN 90-5410-455-4

Wittven and Bos; Deltares (2010): Criteria voor toepassing van bekledingen op waterkeringen;

hulpmiddel vorr ontwikkeling van innovatieve dijkbekledingen, Rotterdam 2004


Book of Abstracts - Session 6: Modeling, Management 91

Mooring lines and module connector forces measurements

with different anchoring typologies. Application to Aguete Port

Javier Ferreras 1 , Antía López 1 , Enrique Peña 1 , Félix Sánchez-Tembleque 2 , Andrea Louro 1

1 Introduction

In the last decades, a significant increase of the use of floating breakwaters has been produced

because of its great environmental benefits. Thus, these ones are commonly used in

recreational harbour protected against waves with long periods. In order to realize an

appropriate design of these structures, it is necessary to study their structural behavior. In this

regard, mooring line typologies play a fundamental role. As it is proven in previous studies

(Peña, 2009), the type of anchoring does not has a considerable influence in the hydrodynamic

behavior of the floating breakwater, but they are of great importance in the loads suffered by the

structure.

In this paper four different kinds of mooring lines have been studied in a physical model of the

floating breakwater located in Aguete (Galicia, Spain) in order to determine the real efficiency of

these typologies of anchoring. For this purpose, mooring lines forces and stress and momentum

between modules have been measured.

2 Physical model

The experiments were conducted in a 32x34m wave tank divided with brick walls to have a 12

meter wide wave front at the R+D Centre of Technological Innovation in Building and Civil

Engineering (CITEEC, www.udc.es/citeec).

The Aguete Port floating breakwater (20x4x1.80m) was modelled as 3 pontoons of stainless

steel, working on a 1:15 scale. Each pontoon was connected to the next one with a cylindrical

neoprene joint, and anchored to the bottom of the wave basin with four mooring lines, being

perpendicular to the pontoon on the extremes and oblique to it in the central dock. The analyzed

sea level was 7.50 m. This set up simulate the real situation in the port.

Figure 1: Physical model of the Aguete Port floating breakwater with oblique incident wave (left)

and detail of the module connector (right).

Four different typologies of mooring lines were used to carry out the tests: a) rigid mooring lines

with a 2 m length chain and catenary shape; and three elastic mooring lines: two of them has an

elastic coefficient of k=30 kN/m, a length of 4 m and are pretensioned to b) 10% and c) 30% of

their elongation in mid tide, whereas the last one d) have an elastic coefficient of k=2.13 kN/m, a

length of 3 m and are pretensioned to 10 %. In addition, a safety by-pass was installed to

prevent an elongation of the elastic anchoring higher than 80%.

Regular wave tests were developed with wave heights from 0.71m to 1.41m, and wave periods

from 4.8s to 18s. Test with oblique incident waves simulate the common wave propagations in

the study zone.

1

Water and Environmental Engineering Group (GEAMA). Civil Engineering School, University of A Coruña. Campus de

Elviña, s/n. 15071, SPAIN (javie.ferreras@udc.es)

2

CITEEC (R+D Centre of Technological Innovation in Building an Civil Engineering), University of A Coruña. Campus

de Elviña s/n. 15071, SPAIN


92 5th International Conference on Applied Coastal Research - SCACR 2011

3 Results and discussion

In the results obtained for the 4 different anchoring, a uniform trend in the mooring lines forces

was observed with a slight increase of the values with wave period and height, reaching peak

values of 14 Tons for the elastic mooring line with k=30 kN/m. With the most elastic typology of

anchoring (k=2.13 kN/m) the maximum values measured in all the different mooring lines

ranges between 0.6 and 0.7 Tons. However, with this typology, and in punctual moments of the

tests of highest wave heights and periods, the safety by-pass works and, then, the efforts reach

values from 4 to 8 Tons. This is due to the anchoring acts as a chain, but without catenary

shape when the by-pass is working.

Vx (Tn)

My(Tn∙m)

18

160

16

140

14

120

12

100

10

8

6

80

60

4

40

2

20

0

T (s) 0

T (s)

0 5 10 15 20

0 5 10 15 20

Figure 2: Module connector forces with oblique waves and elastic mooring lines

Module connector loads also has been measured for the different typologies of anchoring.

Horizontal -Fx- and vertical -Fy- shear stress, and its associated moments (yaw –Mx- and

pitch -Mx-) were recorded. For all the analyzed cases the Mx is negligible compared to the

others load components, which proves that the union behaves almost as a pin. The measured

values are very similar for the three first studied anchoring typologies, with peak values of 20

tons for Fy and Fx, and 130 Tons·m for My. For the most elastic typology analyzed the values

obtained for Fx are similar than the previous ones, but the vertical shear stress -Fy- decrease to

5 Tons and My increase to 150 Tons·m.

4 Conclusions

In this study, 3D and 1D load cells were successfully used to register the module connector and

the mooring lines loads of the floating breakwater, which is innovative and of great importance

in the design of these kinds of structures.

It has been proven that mooring lines forces are considerably reduced using more elastic

anchoring. However, this great decrease of the efforts does not translate into an increase of the

same magnitude in the module connector loads, but to more movements. As a result, mooring

lines with a high elasticity (2.13 kN/m) are very efficient, improving the structural behavior of the

floating breakwater, for the analyzed tide.

Nevertheless, when designing a floating breakwater is very important to take into account the

possible entry into operation of the safety bypass, more likely with mooring lines of high

elasticity, which turn on a great overloads.

5 Acknowledgements

This project was funded by the Regional Port Authority of Galicia (Spain) and Aquática

Ingeniería Civil. Special thanks are due to Fernando Martínez Abella, member of the

Department of Construction Engineering of the University of A Coruña.

Also, the writers would like to thank the economical support of Spanish National Plan of R+D,

Ministry of Science and Innovation, reference project CGL2008-03319/BTE.

6 References

H= 1.41 m H= 1.06 m H= 0.71

Peña. E.; Sánchez-Tembleque, F.; Ferreras, J., Piñón, O.; Rodriguez, J.A.; Urquijo, P. (2009):

Physical modeling of the mechanical and hydrodynamic behavior of reinforced concrete

floating breakwaters. Coasts, Marine Structures and Breakwaters 2009. Edinburg, UK


Book of Abstracts - Poster Presentation 93

Investigation of the effect of permeability on wave interaction

with a barrier by application of PIV

Hany Ahmed 1 , Andreas Schlenkhoff 2

1 Introduction

Integrating a permeable part into a coastal barrier can substantially decrease its environmental

impact. The application of PIV has become state-of-the-art in analysing velocity fields. PIV can

also be used for determination of the reflection and transmission coefficient, which will be

shown in the study. The performance of such structures and their effect on permeability

interacting with waves should be known. Therefore, wave interaction with a permeable wall has

been investigated in a glassed-wall wave flume on a scale model modifying its permeability. The

results gathered by PIV have been compared with the calculated wave particle velocities by the

linear airy theory. The results of PIV are perfectly acceptable. Further on, a velocity distribution

of the incident, co-existing and transmitted wave are recorded and the reflection and

transmission coefficients are calculated via PIV. The calculated reflection and transmission

coefficients by the velocity distribution indicate an efficient performance of the permeable

breakwater to reduce the energy of waves in shoreward.

2 Experiment set-up

2.1 Model runs

The experiments have been conducted on a scale model of M = 1: 25 in the glassed wall wave

flume of the University of Wuppertal. The flume is 24 m long, 0.30 m wide and 0.5 m deep.

Tests were carried out with a constant water depth of d = 0.3 m. The proposed permeable

breakwater model is a single vertical slotted wall and constructed of vertical panels with a width

of 2.5 cm, and a thickness of 2.5 cm. The porosity of the barriers is 50 % in the middle. The

draft of the permeable part is dm=0.2 d. The upper and lower parts are impermeable with a draft

of 0.4 d. The model is tested under regular waves. The wave-frequencies are 2, and 0.75 Hz,

and the corresponding wave heights are 1and 4 cm respectively.

2.2 Measurement of the incident, transmitted and co-existing waves

PIV has been employed to measure the velocity field of the incident, transmitted and co-existing

wave. The wave-frequencies are 2, and 0.75 Hz. The resolutions of the camera are 624x512

and 1200x704 (square pixels), the field of views are 22.5x18.5 and 42.5x24.5 cm 2 , the sampling

intervals are 0.001 and 0.002 s and the time increments are 0.008 and 0.014 s respectively.

The model is situated in a distance of one wave length in front of the centre of Field Of View

(FOV) for transmission measurements and situated in a distance of one wave length in behind

of the centre of FOV for reflection measurements. The measurements are performed at 12.2 m

from the wave maker for incident, transmitted and reflected waves. Tests were carried out

using a high speed camera (Motion Scope M3. The analysis of the wave velocities are

conducted by Mat PIV (Sveen 2004)

3 Selected Results

Figure 1 illustrates the horizontal velocity distribution at the crest of incident, co-existing and

transmitted wave for a frequency of f = 0.75 Hz (high intermediate waves). Generally, the

amplitude of horizontal velocity decreases with depth. Note that at intermediate waves the orbits

diminish in amplitude with depth. The orbits of incident and transmitted wave in good agreement

1

Irrigation and Hydraulic Department, Al-Azhar University, Egypt. PhD. Student at Wuppertal University, Germany.

E-mail: hanygo32177@yahoo.com.

2 Hydraulic Engineering Section (IGAW), Civil Engineering Department, Wuppertal University, Germany


94 5th International Short Conference on Applied Coastal Research - SCACR 2011

with the linear airy theory but the co-existing wave are different somewhat. The reflection

coefficient can be calculated in terms of the measured velocities. Therefore, the hydrodynamic

performance of this model can be investigated through the horizontal velocity distribution of the

incident and transmitted wave where the velocity is a measure of wave energy. It is noted that

the reflection and transmission coefficients which have been measured by PIV are compatible

with the results of a numerical simulation by an Eigen function expansion method (Ahmed and

Schlenkhoff, 2010) and are compatible with the experimental results by Ultrasonic wave

gauges. The permeable structure shows an encouraging performance.

Figure 1: The horizontal velocity of incident, co-existing and transmitted waves at phase of the

wave crest for a frequency of f = 0.75 Hz

4 Conclusions

This study describes the measurement of the velocity field induced by an incident, transmitted

and reflected wave through a permeable barrier. PIV has been employed for this measurement

as well as for determining the reflection and transmission coefficients. The permeable structure

shows an encouraging performance.

5 References

Sveen, J. K., 2004. “An introduction to MatPIV v. 1.6.1.” Department of Math. Mechanics and

applied Mathematics, , No. 2, University of Oslo, Norwegen.

Ahmed, H. & Schlenkhoff, A., 2010. ''Wave interaction with vertical slotted wall'' In Proc.1st

International Conf. on Coastal Zone Management of River Deltas and Low Land

Coastline, Egypt. Session 8, pp 33-48.


Book of Abstracts - Poster Presentation 95

Monitoring phases of the re-naturalization process of the Torre

del Porto beach

Corrado Altomare 1 , Girolamo Mauro Gentile 2

1 Introduction

The shingle beach of Torre del Porto nearby the town of Mattinata (Italy) showed, since 1980, a

steady decrease in the total volume of the sediments. This volume depletion, slow in its initial

phase, it has led to a retreat of the beach dramatically highlighted as a result of storms

occurring in December 2002. About 600 m of beach disappeared, concrete fences were torn

down and the waves attacked also facing private property.

For the identification of project environmental guidelines which raised certain remedy erosion

was adopted an innovative methodology. The methodology, with the help of the "Perfect Storm"

software (G.M. Gentile), once the natural process that led to the formation of the beach was

discovered, identified the causes which led to the crisis and pointed to the same process design

lines through which he obtained the re-naturalization or beaches.

Once that the first reason of the crisis of the natural process of formation of Mattinata beach

was identified in the lack of contribution of sediment to the coast from hinterland, and verified

the “energy closure "of the bend in which the beach is set, the project involved to entrust

assorted rubble limestone of calculated size with the sea action, in identified points. In this way

the natural formation process could unfold again its effectiveness and shingle beach is back on

board the coast of Mattinata. This project, in order to increase knowledge of the complex

phenomena taking place, was supported by the execution of an innovative monitoring, showed

here.

2 The monitoring phases

The carried out monitoring tried to understand the kinematics of the moving the stones placed,

due to the breaking waves, and to calculate the correlation between the energy applied by the

waves, the unit weight of the stone and the point of release of the same stone along the beach.

The monitoring has identified the effects of beach nourishment performing the following steps:

1) Analysis of energy data affecting the coastal dynamics;

2) Tracking all movement through stone sample.

3 The analyisis of the energy data

This phase consists of:

1. installation, in the centre of the bend, of an anemometer;

2. topographical relief of the beach;

3. implementation of the "Perfect Storm" program taking as input data wind data and the

relief of the beach referred to in points 1) and 2);

1

PhD, Laboratori d’Enginyeria Marítima (LIM), Universitat Politecnica de Catalunya (UPC), Jordi Girona, 1-3, Edif. D1,

Barcelona, 08034, Spain, corrado.altomare@upc.edu

2

Civil and environmental engineering Department (DICA), Technical University of Bari, via E. Orabona, Bari, 70125,

ITALY, gentilegirolamo@libero.it


96 5th International Short Conference on Applied Coastal Research - SCACR 2011

4. identification, by the "Perfect Storm" program, of windstorms provoked storms of which

reached the beach of Torre del Porto and determination of their associated length,

height and wave period;

5. calculation of the energy flows (FE) that each of the identified storm surges has applied

to each of the straight sections, that outlined the coast profile;

6. calculation, for each section, of the balance of energy flows related to all the storms

calculated by the program.

4 Monitoring through sample stones

To verify the development, along the beach, of the energy flows calculated with the "Perfect

Storm" or to identify the kinematics of the placed stones, were searched, in the hours

immediately following each storm, the sample stones placed along the coast.The sample stones

were placed along sections, at a height of -3m,-2m,-1m, 0.00, +1 m and +2 m referred to SWL.

In each point was put a double stone sampling each made of 7 stones with weights of 4, 3, 2, 1,

0.8, 0.6 and 0.4 kg. To identify the origin location of each deposited sample stone and

subsequently moved from the waves, each element of the sample has been properly encoded.

In the first monitoring phase encoding was made by applying a colour code that indicates the

section of origin and percentage of deposition.

In the second and third phase of monitoring the tagging instead occurred via insertion in each

sample stone of a tag trasponder smart label (13.56 MHz standard ISO 15693/ISO radio

frequency identification, RF-iD ). By means of this label, the information about the point of

deposit of the stone, its weight and so on, were registered. The preparation of the sample stone

was completed by applying a small piece of metal necessary to find the stone using a metal

detector.

5 Conclusions

The sample stones found at the end of the storms occurred during the three phases of

monitoring have begun to provide information and verification on the resumption of the "natural

process" of formation of the Torre del Porto beach.

It was confirmed the cause-effect relationship between the energy flows along the coast (FE),

caused by the storm waves and calculated by means of "Perfect Storm" program, and

movement of stones placed on the coast.

Finally the monitoring is able to explain the complex kinematics of displacement of placed

stones due to the breaking and to calculate the relationship between the energy applied by the

waves and the unit weight of stones according to the point of stones placing along the same

beach.

6 References

Gentile, Giasi (2000): I meccanismi dell'erosione costiera per il recupero della costa di Trani.

Atti del convegno GeoBen.

Gentile, Selicato (2002): Pianificazione e gestione dei sistemi costieri marini. Ipotesi di

naturalizzazione e recupero di coste urbane in Puglia. Atti dell’International Conference

Landscapes of Water.

Gentile, Giasi (2003): An example of eco-compatible methodology for coastal remodelling. Atti

dell’European Conference on Application of Meteorology Roma 2003.

Gentile, Giasi (2001): Costruzione di una spiaggia con sterili di cava. Una metodologia di

intervento ambientale ecocompatibile. Pubblicato sulla rivista Geoingegneria Ambientale

e Mineraria.


Book of Abstracts - Poster Presentation 97

Numerical simulation on the motion of cubic armour block

Susumu Araki 1 , Saki Fujii 2 and Ichiro Deguchi 3

1 Introduction

The motion of armour blocks on coastal structures has been computed with Discrete Element

Method (DEM). Araki et al. (2002) computed the deformation of a rubble mound seawall.

Latham et al. (2007) and Sakai et al. (2008) simulated the motion of wave dissipating blocks by

using the model in which the position of each sphere-element is corrected after calculating the

motion of the sphere in order to keep the shape of a wave dissipating block.

The final goal of this study is to compute the motion of armour blocks with a complicated shape

using the concept of DEM without the model in which the relative motion between spheres is not

allowed. In this study, the motion of the cubic armour blocks was calculated as a first step.

2 Numerical Procedure

2.1 Governing Equations

The DEM is the method of simulating large deformation by calculating the motion of every

element. The governing equations are the equations of motion in the x-, y- and z-directions for

the center of gravity of each cubic armour block and the rotational equations around the axes

which go through the center of gravity of each armour block and are parallel to the x-, y- and zaxes,

respectively. The equation of motion and the rotation equation for the cubic armour block i

are as follows:

m u� � F

(1)

i

i

iG

iG

i

I �� � M

(2)

i

with m i mass of the armour block i [kg]

u iG velocity vector of the center of gravity of the armour block i [m/s]

F i force vector acting on the armour block i [N]

I i inertia moment of the armour block i [kg m 2 ]

� iG angular velocity vector around the center of gravity of the armour block i [rad/s]

M i moment vector acting on the armour block i [Nm]

The inertia moment of an armour block varies depending on the rotation of the armour block

except for a sphere. However, the inertia moment around each axis for a cube was assumed to

be a constant for simplicity in the present study. The positions of the vertices of each cubic

armour block are calculated from the motion of the center of gravity, the rotational angle around

the center of gravity and the distance between the position of the vertex and the rotational axis.

2.2 Judgement of Contact

The contact of two cubic armour blocks i and j was judged from the contact of the planes

consisting of armour blocks i and j. The exerted force between two cubic armour blocks by their

1

Dept. of Civil Engineering, Osaka University, 2-1 Yamada-oka, Suita, Osaka 565-0871 Japan,

araki@civil.eng.osaka-u.ac.jp.

2

Dept. of Civil Engineering, Osaka University, 2-1 Yamada-oka, Suita, Osaka 565-0871 Japan

3

Dept. of Civil Engineering, Osaka University, 2-1 Yamada-oka, Suita, Osaka 565-0871 Japan,

deguchi@civil.eng.osaka-u.ac.jp


98 5th International Short Conference on Applied Coastal Research - SCACR 2011

contact was expressed by an elastic spring and a viscous dashpot. The contact forces were

assumed to act in the direction between the center of gravities of the two armour blocks � and in

the two rectangular directions � and � on the plane normal to the direction �. Torsional moment

was neglected in the present study.

3 Example of Simulated Result

The falling of a wooden cube in the air and the collision with a fixed cube were measured from

the video image. The result simulated by the model developed in this study was in good

agreement with the measured one. A trial simulation was conducted on the basis of the verified

result. Figure 1 shows the bird’s-eye view (x-y-z) and the elevation view (x-z) (only in t = 0.0s) of

the trial simulation. A cube drawn in a bold line falls onto the cubes placed like steps in the air.

The placed cubes drawn in a thin line were not moved. Figure 1(b) shows the snapshot just

before the moment when the falling cube collided with the placed cube. After the collision, the

cube rolled down the cubes placed like steps (Figures 1(c)-(e)).

elevation view

(a) t = 0.0s (b) t = 0.06s

(c) t = 0.26s (d) t = 0.46s (e) t = 0.66s

Figure 1: Motion of a cube above fixed cubes

4 References

Araki, S.; Kotake, Y.; Kanazawa, T.; Matsumura, A.; Deguchi, I. (2002): Development of

numerical simulation method for predicting deformation of rubble mound seawall with

VOF method and DEM, in: Proceedings of the 28th Int’l Conference on Coastal Eng.,

pp. 1485-1497. ISBN 981-238-238-0. Cardiff, Wales.

Latham, J.-P.; Mindel, J.; Guises, R.; Gracia, X.; Xiang, J.; Pain, C.; Munjiza, A. (2007): Coupled

FEM-DEM and CFD for coastal structures: application to armour stability and breakage,

in: Proceedings of the 5th Coastal Structures Int’l Conference, pp. 1453-1464. ISBN -13

978-981-4280-99-0. Venice, Italy.

Sakai, T.; Harada, E.; Gotoh, H. (2008): 3D Lagrangian simulation of compaction process of

wave dissipating blocks due to high waves, in: Proceedings of the 31st Int’l Conference

on Coastal Eng., pp. 3412-3422. ISBN-13 978-981-4277-36-5. Hamburg, Germany.


Book of Abstracts - Poster Presentation 99

Estimation and verification of long-shore sediment transport at

Lecce coastline

Elvira Armenio 1 , Felice D’Alessandro 1 , Francesco Aristodemo 2 and G. Roberto Tomasicchio 1

1 Introduction

Accurate predictions of the total rate of longshore sand transport (LST) and its cross-shore

distribution pattern in the surf zone are central to coastal engineering studies. As an example,

the design of coastal protection structures (breakwaters, groynes) and beach nourishment

projects relies on assessment of their impact on the shoreline that is often the result of gradients

in the LST rate.

Present understanding and methods for calculating the LST rate are largely developed based

on field and laboratory studies (e.g. Komar and Inman 1970, Kraus et al. 1989, Dean 1989,

Schoonees and Theron 1993, Wang et al. 1998, Smith et al. 2003, Kumar et al. 2004).

The most popular formula for LST is commonly known as the CERC equation (USACE 1984).

This method is based on the principle that the longshore transport rate, including bed load and

suspended load, is proportional to longshore wave power, P, per unit length of beach: LST = K

P, with K = calibration coefficient. The expression is best used if K is calibrated using data for a

particular site. For design applications with adequate field measurements, the CERC formula

can be calibrated and applied to estimate LST rates with ± 50 percent of confidence. However,

for sites without available transport data to calibrate K, the CERC formula provides only order of

magnitude accuracy (Fowler et al. 1995, Wang et al. 1998). The effects of particle diameter and

bed slope, neglected in the CERC formula, have been studied systematically by Kamphuis

(1991), resulting in a more refined equation for longshore sediment transport. This latter

equation was found to give the best agreement between computed and measured transport

rates (Schoonees and Theron 1996). More recently, Bayram et al. (2007) proposed a new

predictive formula for the LST rate, developed from principles of sediment transport physics

assuming that breaking waves mobilize the sediment, which is subsequently moved by a mean

current.

The purpose of the present paper is to examine the accuracy of commonly used tools (USACE

1984, Kamphuis 1991, Bayram et al. 2007) to estimate the LST for the case of the coastline of

Lecce, Italy. The estimates of potential annual rate of LST from the different adopted formulas

will be compared and analyzed in a case study.

2 The case study

The study area is the coastline of Lecce, on the southern Adriatic coast of the Apulia region, in

Italy (Figure 1). This area, well known as Salento, presents fine sandy beaches characterized

by gentle cross-shore slopes.

The wave climate is determined based on data from the National Sea Wave Measurement

Network (RON) (available online, http://www.idromare.com). Since 1989, RON have provided

measurements of the wave characteristics in Italian seas under deep water conditions with

reliable results in terms of data acquisition rates and temporal coverage. The considered buoy

is located offshore of Monopoli (70 m water depth), 100 km north of Lecce. The recorded mean

annual offshore wave height is ≈ 2.0 m with typical wave periods of 4-6 s. However, during

intense storms, offshore wave heights may exceed 5 m with peak spectral wave periods of 10-

1

Engineering Department, University of Salento, via per Monteroni, Ecotekne, 73100 Lecce, Italy

elvira.armenio@unisalento.it; felice.dalessandro@unisalento.it; roberto.tomasicchio@unisalento.it

1

Department for Soil Conservation, University of Calabria, Ponte P. Bucci Cubo 42B, 87036 Arcavacata di Rende, Italy

aristotool@gmail.com


100 5th International Short Conference on Applied Coastal Research - SCACR 2011

13 s. The effective wave climate at a “virtual” buoy located in front of the study coast is derived

by the application of the “geographical transposition” method to the directional wave records of

the RON buoy of Monopoli. Wave nearshore transformation analysis is carried out to calculate

the propagated wave characteristics in terms of significant wave height, Hsb, and wave angle,

θb, at breaking.

The annual net LST along the Adriatic coast of Salento is southward directed resulting from

waves approaching the coastline in the sector from north-west to north-north-east compared to

their counterparts from east-north-east to east-south-east (Figure 1). Actual LST rate values will

be determined by means of successive aerophotogrammetric surveys and compared with the

calculated values from the three adopted formulas.

Figure 1: Areal view of the study coast and the local wave climate

3 References

Bayram, A., Larson, M., Hanson, H. (2007): A new formula for the total lonshore sediment

transport rate. In: Coastal Engineering, Elsevier, (54) 700-710.

Dean, R.G. (1989): Measuring longshore sediment transport with traps. In: Nearshore sediment

transport. R.J. Seymour, ed., Plenum Press, New York, 313-337.

Fowler, J.E., Rosati, J.D., Hamilton, D.G., and Smith, J.M. (1995): Development of a large-scale

laboratory facility for longshore sediment transport research. In: The CERCular, CERC-

95-2, U.S. Army Engineer Waterways Experiment Station, Vicksburg, MS.

Kamphuis, J.W. (1991): Alongshore sediment transport rate. In: Journal of Waterway, Port,

Coastal and Ocean Engineering, ASCE, 117(6), 624-641.

Komar, P.D., and Inman, D.L. (1970): Longshore sand transport on beaches. In: Journal of

Geophysical Research 75 (30), 5914-5927.

Kraus, N.C., Gingerinch, K.J., Rosati, J.P. (1989): Duck85 surf zone sand transport experiment.

U.S. Army Engineer Waterways Experiment Station, Tech. Report CERC-89-5.

Kumar, V.S., Anand, N.M., Chandaramohan, P., Naik, G.N. (2004): Longshore sediment

transport rate; measurements and estimation Central West Coast of India. In: Coastal

Engineering, Elsevier, (48) 95-104.

Schoonees, J.S., and Theron, A.K. (1993): Review of thee field data base for longshore

sediment transport. In: Coastal Engineering, Elsevier, (19) 1-25.

Smith, E.R., Wang, P., Zhang, J. (2003): Evaluation of the CERC formula using large-scale

model data. U.S. Army Engineer Research and Development Center, Coastal and

Hydraulics Laboratory, Vicksburg, MS.

USACE (1984): Shore Protection Manual. Department of the Army, U.S. Corps of Engineers,

Washington, DC 20314.

Wang, P., Kraus, N.C., and Davis Jr., R.A. (1998): Total rate of longshore sediment transport in

the surf zone: field measurements and empirical predictions. In: Journal of Coastal

Research 14(1), 269-283.


Book of Abstracts - Poster Presentation 101

Developing sustainable coastal protection- and management

strategies for Schleswig-Holstein’s Halligen considering

climate changes (ZukunftHallig)

Arne Arns 1 , Hilmar von Eynatten 2 , Roger Häußling 3 , Dirk van Riesen 4 , Holger Schüttrumpf 5 and

Jürgen Jensen 1

1 Scope

With an area of approximately 9.000 km², the depositional coastline of the Wadden Sea is one

of the world’s largest intertidal wetlands. In 2009, the Wadden Sea was added to UNESCO´s

World Heritage List. Besides its ecological and historico-cultural relevancy, the Wadden Sea

itself is an important element of coastal protection. Surrounded by the North Sea, the Wadden

Sea includes 10 marsh islands called Halligen. These small islands are a natural phenomenon,

which is unique worldwide. Although the Halligen are inhabited by around 300 residents, the

Halligen have no dikes. Consequently, the Halligen are inundated up to 50 times a year. In

order to protect themselves from these inundations, houses are built on dwelling mounds.

Residents learned to cope with these extreme conditions, but as time goes by, the Halligens'

shapes and conditions are gradually negatively affected, especially in consequence of rising

sea levels.

Figure 1: Picture of Hallig Gröde from 1984. While huge parts are inundated, the dwelling

mounds are still above sea level.

1 Research Institute for Water and Environment (fwu), University of Siegen, email: arne.arns@uni-siegen.de

2 Geoscience Center, University of Göttingen

3 Institute of Sociology, Aachen University

4 Schleswig-Holstein Agency for Costal Defence, National Park and Marine Conservation, Husum

5

Institute of Hydraulic Engineering and Water Resources Management, RWTH Aachen University,

schuettrumpf@iww.rwth-aachen.de

6 Institute of Hydraulic Engineering and Water Resources Management, Aachen University


102 5th International Short Conference on Applied Coastal Research - SCACR 2011

According to Meehl et al. (2007), sea level is predicted to increase by 30 cm to 100 cm by 2100.

Among others, these changes are directly affecting the ability of disturbance regulation of the

Wadden Sea while ocean currents and sediment fluxes are influenced and the Halligens'

flooding frequency increases. Coastal ecosystems are known to be dynamic with a certain

capacity of compensating changes in the Mean Sea Level (MSL) by non-linear feedback

mechanisms. However, observations are indicating limits in this adaptability (Kirwan et al.

2010).

2 Extent of work

Within the joint research project “ZukunftHallig”, an interdisciplinary team of researchers is

investigating the future development of the Halligen considering climate changes. The project

aims for the development of new impulses to sustainable coastal protection- and management

strategies, focusing on the protection and preservation of the Halligen.

In particular, the hydrodynamic forcing of today and future conditions as well as morphological

and sedimentological changes will be investigated. Therefore, local Sea levels and extreme

water levels as well as their interaction are going to be analysed. For estimating the future

sedimentation on the Halligen, analyses on both the duration and the depth of inundations and

their correlation with sedimentological data is of particular interest.

Following a quantification of the current protection standard, a risk based hazard analysis will be

conducted. This analysis serves as input for creating the above mentioned, sustainable coastal

protection- and management strategies. Finally, the acceptance of these strategies among the

residents will be elicited.

Due to the comprehensive work schedule, the study will be conducted for only three of the

overall ten existing Halligen exemplarily. These are Langeneß, Nordstrandischmoor and Hooge.

The intention of the research project is to gain insights into the processes involved in the

evolution of the Halligen, which is the basis for an effective and sustainable protection strategy.

3 Acknowledgements

This is a German Coastal Engineering Research Council (KFKI) project, funded by the German

Federal Ministry of Education and Research (BMBF) (Project No. 03KIS096). We would like to

thank these funding bodies for making this project possible.

4 References

Meehl, G. A., et al. (2007), Global climate projections, in Climate Change Fourth Assessment

Report of the Intergovernmental Panel on Climate Change, edited by S. Solomon et al.,

pp. 747– 845, Cambridge Univ. Press, Cambridge, U. K.

Kirwan, M. et al. (2010): Limits on the adaptability of coastal marshes to rising sea level. In:

Geophysical Research Letters, Vol. 32., doi:10.1029/2010GL045489.


Book of Abstracts - Poster Presentation 103

Artificial surfing reefs – an option for the German Baltic Sea

coast?

M.Sc. Marcus Behrendt 1

1 Introduction

The sport of surfing is the art of riding a wave and is more than 200 years old. Nowadays it is a

billion dollar industry with millions of people practicing it. Since several years artificial reefs are

built to improve the surfing conditions at a specific location. These artificial reefs are mostly built

from submerged geosynthetic megacontainers filled with sand. These containers are shaped in

a way to influence the shallow water effects of the incoming waves. In detail this means that the

processes of shoaling, refraction and wave breaking are significantly influenced. As a result the

surfing conditions can be changed in a specific way and a unique wave can be “created”. That

offers the surfer special features other waves don’t have. At the same time the artificial reef

works like a submerged breakwater. Therefore it can have an impact on the evolution of the

coast around the reef. This could be used as a method for coastal protection. For good surfing

conditions at a reef, specific sea state conditions in general are needed. The main features of a

surfing reef and the possibility of building it at the German Baltic coast are discussed in this

paper.

2 Effects of an artificial reef on the wave climate

There are three main purposes of the reef (figure 1).

1. Refraction – on the first part of the reef, which is shaped like a ramp with a small slope

angle, the incoming waves are refracted towards the favoured orthogonal direction.

2. Shoaling – when the slope angle increases, the process of shoaling becomes significant

and the waves are getting higher before they start to break.

3. Wave breaking - waves with a defined size or bigger will break at the end of the reef

along the crest of the reef.

Figure 1: aerial view of an artificial surfing reef (left), functional parts of an artificial surfing reef

(right)

3 Improvements on the surfing conditions

The main improvement that is caused by the reef is the controlled breaking of the waves at the

crest of the reef. Depending on the angle between the reefcrest and the incoming waves the

level of difficulty of surfing this wave can be influenced. The smaller the so called peel angle is,

the more difficult it is to surf the wave. The reef can have several parts with different peel

angles, so the reef can be surfed by beginners and advanced surfers. Furthermore it is possible

to create local features by including for example a pinnacle or ridge in the crest of the reef. With

these tools it is possible to design the characteristics of the breaking waves.

1 Coastal Engineering Group, University of Rostock, Faculty of Agricultural and Environmental Sciences, Justus von

Liebig Weg 6 LAG II, 18059 Rostock, Germany, marcus.behrendt@uni-rostock.de


104 5th International Short Conference on Applied Coastal Research - SCACR 2011

4 Wave climate at the German Baltic coast and the consequences for

a surfing reef

The reefs that have been built over the world in the last years were all situated at locations

where long period swell was dominating the sea state. The advantage of this fact for the design

process is based on the small directional spreading θ of long travelled swell, which makes it

easier to align the reef according to the dominant swell direction

The German coast, especially the German Baltic coast is not dominated by swell but by wind

waves. They are characterized by a great directional spreading and a great variation of the

significant wave height Hs. Despite of these facts it is possible to design a surfing reef for this

kind of conditions.

The Baltic Sea is a very shallow sea. Therefore the process of refraction is taking place very

early while the waves are reaching the near shore region. Even if wind waves have a great

directional spreading, they are refracted towards the favoured orthogonal direction by the

shallow shore in the Baltic Sea. When the waves reach the beginning of the reef, they are

already refracted by a significant dimension. The great variation in the wave height cannot be

changed but by defining a minimum wave height that is breaking on the reef crest, it can be

calculated how often the reef would “work”. By calculating the efficiency of the reef it is possible

to decide if the building of a reef with the defined dimension is making sense.

For the German Baltic coast this calculation has been done on the basis of a dataset of wind

measurements over 20 years. Based on these measurements an averaged percentage sea

state distribution of the wave heights depending on the direction was calculated. This sea state

distribution was filtered with a minimum wave height (Hs = 1,0 m) and the significant direction of

wave approach according to the specific region (figure 2).

Figure 2: visualization of significant wave heights and their incident wave angle near Rostock

(left), sea state distribution filtered for the specific location (right)

The calculations show that at the German Baltic coast a surfing reef designed for a minimum

significant wave height of Hs = 1,0 m the degree of efficiency is below 10 %. With building costs

of round about two million Euros, such a project with the single purpose of improving the surfing

conditions is hard to finance. If there would be the possibility to identify other benefits of the

artificial reef, for example coastal protection, maybe the financing could be realized. The

positive effects for the maritime tourism and the local sport and youth culture could also

influence the decision makers to build an artificial surfing reef at the German Baltic coast.

5 References

Fröhle, P.; Horlacher, H. (2006): Bemessungsseegang Außenküste Mecklenburg-Vorpommern

– Abschlussbericht (german),

Mead, S.; Black, K. (2001): Field Studies Leading to the Bathymetric Classification of World –

Class Surfing Breaks. In: Journal of Coastal Research Special Issue No. 29,p.5-20;

ISSN 07490208

Walker, J. (1974): Recreational Surf Parameters. LOOK Laboratory TR-30, University of Hawaii,

Honolulu


Book of Abstracts - Poster Presentation 105

Abrasion rates of marked pebbles on two coarse-clastic

beaches at Marina di Pisa, Italy

Duccio Bertoni 1 , Giovanni Sarti 2 , Giuliano Benelli 3 and Alessandro Pozzebon 4

1 Introduction

Tagging individual pebbles with devices that enable an easy detection is a methodology that

has been often used recently (Allan et al., 2006; Bertoni et al., 2010). A useful application of this

method concerns the measurement of sediment in situ abrasion, which makes up for a more

complete dataset rather than laboratory tests. First laboratory experiments about sediment

abrasion involved measurements under conditions that only simulate the physical processes

acting on a beach (Kuenen, 1964; Latham et al., 1998; Nordstrom et al., 2008). After preliminary

attempts by Zhdanov (1958), only recently the abrasion of individual pebbles was reckoned

(Dornbusch et al., 2002). The aim of the study is to measure the abrasion rate of individual

pebbles of different grain-size and shape, highlighting the differential weight loss on two artificial

coarse-clastic beaches (Cella 7 and Barbarossa) at Marina di Pisa (Tuscany, Italy). Although

similar in configuration, Cella 7 and Barbarossa present some differences that lead eventually to

different abrasion rates: the length (Cella 7 is 250 m long; Barbarossa is just 110 m long) and

the presence of a submerged breakwater 50 m off the coastline at Cella 7.

2 Methods

Coarse sediments were traced by means of the RFID (Radio Frequency Identification)

technology, which proved a reliable method to track particles on the subaerial portion of a beach

(Allan et al., 2006) and even underwater (Bertoni et al., 2010). The pebbles (20-to-90 mm in

mean diameter) were sampled on the beach and prepared for the experiment according to the

procedure described in Bertoni et al. (2010). This procedure should minimize undesired effects

on the textural properties of the tracers. The pebbles were accurately weighed by means of an

electronic scale (instrument error of 0.1 g), and photographed. About 200 tracers were then

released on the beaches along transects normal to the coastline. The small transponder

coupled to the pebbles made the tracers unequivocally identifiable. They were detected by a

mobile antenna, which allowed the recovery of the marked. The detection range of the antenna

reached 40 cm, and it was often difficult to dig up those pebbles that were transported toward

the step and then buried.

3 Results and discussion

The recovery campaign was performed two months after releasing the tracers. Eighty-one

pebbles were detected, 52 on Cella 7 and 29 at Barbarossa (Tab. 1). The recovery rate at the

two beaches was different due to the stronger reworking that sediments underwent at

Barbarossa.

Table 1: Number of released (RS pbs) and retrieved (RT pbs) pebbles with the average weight

loss (AVL) reckoned after the experiment on Cella 7 and Barbarossa beaches.

Beach RS pbs RT pbs AWL (%)

Cella 7 96 52 2.4%

Barbarossa 102 29 10.2%

1 Department of Earth Sciences, University of Pisa, Via S. Maria 53, 56126 Pisa, Italy, bertoni@dst.unipi.it

2 Department of Earth Sciences, University of Pisa, Via S. Maria 53, 56126 Pisa, Italy, sarti@dst.unipi.it

3 Department of Information Engineering, University of Siena, Via Roma 56, 53100 Siena, Italy, benelli@unisi.it

4

Department of Information Engineering, University of Siena, Via Roma 56, 53100 Siena, Italy,

alessandro.pozzebon@unisi.it


106 5th International Short Conference on Applied Coastal Research - SCACR 2011

The submerged breakwater fronting Cella 7 is effective in decreasing the energy of the

incoming waves, and sediment mobilization is not as intense as at Barbarossa, where there are

no offshore structures (Bertoni et al., 2010). At Cella 7, the results showed a slight weight

decrease for every tracer, on average 2.4%. The abrasion rate attained at Barbarossa was quite

different, reaching an average of 10.2%. Pebbles that were placed on the fair-weather berm

showed a higher abrasion rate than any other starting positions. Considering the brief time

frame of the study and the occurrence of only three storms, the average abrasion rate that was

reckoned on the recovered pebbles has been noteworthy (Fig. 1). The difference in weight loss

between the two study sites is determined by the higher energy of the waves at Barbarossa,

due to the absence of the submerged breakwater, which causes higher mobilization of the

sediments. The higher abrasion rate of the tracers that were injected on the fair-weather berm is

related to the intense mobilization of that portion of the beach even during fair-weather periods.

Figure 1: Pictures of a marked pebble before (left) and after (right) the experiment.

4 Conclusions

This research highlighted once again the efficiency of the RFID technology as a mean to trace

and detect coarse-grained sediments, which is paramount to assess and evaluate the

modification of sediment textural properties such as the abrasion directly on site and not only in

laboratory. The measured abrasion of about 10% on pebbles sampled on the beach is

significant considering the short span of time of the experiment and the limited energy of the

storms. Measuring in situ abrasion rates of pebbles might be useful to improve and optimize

future coarse-clastic beach fills, which are more consistently used as a form of protection from

coastal erosion.

5 References

Allan, J. C.; Hart, R.; Tranquilli, V. (2006): The use of Passive Integrated Transponder (PIT)

tags to trace cobble transport in a miced sand-and-gravel beach on the high-energy

Oregon coast, USA. In: Marine Geology, Vol. 232, pp. 63-86.

Bertoni, D.; Sarti, G.; Benelli, G.; Pozzebon, A.; Raguseo, G. (2010): Radio Frequency

Identification (RFID) technology applied to the definition of underwater and subaerial

coarse sediment movement. In: Sedimentary Geology, Vol. 228, pp. 140-150.

Dornbusch, U.; Williams, R. B. G.; Moses, C.; Robinson, D. A. (2002): Life expectancy of

shingle beaches: measuring in situ abrasion. In: Journal of Coastal Research, Vol. SI

36, pp. 249-255.

Kuenen, P. H. (1964): Experimental abrasion: 6 surf action. In: Sedimentology, Vol. 3, pp. 29-

43.

Latham, J. P.; Hoad, J. P.; Newton, M. (1998): Abrasion of a series of tracer materials on a

gravel beach, Slapton Sands, Devon, UK. In: Latham, J. P. (ed.) Advances in

Aggregates and Armourstone Evaluation. Geological Society, London, Engineering

Geology Special Publications, Vol. 13, pp. 121-135.

Nordstrom, K. F.; Pranzini, E.; Jackson, N. L.; Coli, M. (2008): The marble beaches of Tuscany.

In: The Geographical Review, Vol. 98, pp. 280-300.

Zhdanov, A. M. (1958): Attrition of pebbles under the wave action. In: Bulletin of the

Oceanographic committee of the USSR Academy of Sciences, Vol. 1, pp. 81-88.


Book of Abstracts - Poster Presentation 107

Risk assessment for North Sea coastal lowlands in Germany

Holger Blum 1 , Frank Thorenz 2 and Hans-Jörg Lambrecht 3

1 Introduction

On its northern side the German Federal State Lower Saxony borders the North Sea. The

coastal lowlands of Lower Saxony represent an important economical, agricultural, cultural and

ecological area. Due to height levels ranging from below to a few meters above mean sea level,

about 6600 km², 1/7th of the total state area, is flood proned by storm surges. A coastal defence

system, consisting for the mainland coast of levees, storm surge barriers, forelands and

secondary levee lines provides flood protection for 1.2 million inhabitants. By these elements a

flood protection line with a total length of 610 km is formed.

The present coastal defence strategy for the flood prone areas and a legal safety level are

defined in the “Generalplan Küstenschutz Niedersachsen / Bremen” (Master Plan Coastal

Defence, NLWKN 2007) and the Lower Saxony Flood Defence Law (NDG, 2010) as a legal

basis. According to the EU Flood Risk Management Directive, for areas with potential significant

flood risks, flood hazard maps and flood risk maps as well as flood risk management plans have

to be prepared. Aspects of flooding due to failure of coastal defences and the consequences

are investigated by the Lower Saxony Water Management, Coastal Defence and Nature

Conservation Agency (NLWKN) within two research projects SAFECOAST (Safecoast, 2008)

and HoRisK (Hochwasserrisikomanagement für den Küstenraum) in order to facilitate the

directives implementation.

2 Hazard classification, flooding simulation and damage calculations

Within the European project SAFECOAST five North Sea states jointly investigated

perspectives for an improved coastal risk management in the North Sea Region. The

subprojects focussed on methods of risk based evaluation of flooding consequences and the

risk awareness of potentially affected people. Within the sub-project executed by NLWKN,

typical locations of the coast were used for case studies to investigate the vulnerability of the

hinterland against failure of levees. By means of numerical models the effects of scenario based

breaches and the flood wave propagation as well as extension were calculated (Fig. 1).

The economic damage caused by flooding scenarios was evaluated based on meso-scale

damage potential mapping, using a GIS-System. The results show significant differences in

vulnerability of certain stretches of the coast and provide important hints for disaster

management and risk mitigation.

Within the KFKI-Research project HoRisK carried out by the Universities of Aachen, Rostock

and the NLWKN, aspects mentioned above are to be further investigated in the subproject

HoRisK-C – consequences of flooding in the North Sea coastal area and damage minimization -

lead by NLKWN.

As first phase of the project a desktop study covering the entire coastal defence system of the

Lower Saxony mainland was conducted. The study provides distributions of terrain levels for

certain low lying and flood-protected coastal areas derived from GIS-based analysis. Mapping

and analyzing the spatial allocation of specific coastal defence systems, e.g. main levees with a

second levee line situated landwards or forelands, is supplemented by integration of remote

sensing elevation information in combination with ATKIS data (Authoritative Topographic-

1 Lower Saxony Water Management, Coastal Defence and Nature Conservation Agency (NLWKN), Jahnstrasse 1,

26506 Norden, Germany, holger.blum@nlwkn-nor.niedersachsen.de

2 Lower Saxony Water Management, Coastal Defence and Nature Conservation Agency (NLWKN), Jahnstrasse 1,

26506 Norden, Germany, frank.thorenz@nlwkn-nor.niedersachsen.de

3 Lower Saxony Water Management, Coastal Defence and Nature Conservation Agency (NLWKN), Jahnstrasse 1,

26506 Norden, Germany, hans-joerg.lambrecht@nlwkn-nor.niedersachsen.de


108 5th International Short Conference on Applied Coastal Research - SCACR 2011

Cartographic Information System). A terrain level distribution for protected area was obtained.

Figure 2 shows exemplary the situation for the area in responsibility of the water board

Krummhörn located in the north-west of Lower Saxony. Significant parts of the analyzed area

show a terrain level below mean high tide. In case of a failure of the coastal defences even

regular tides affect the hinterland if a breach cannot be closed rapidly. Numerical hydrodynamic

flooding simulations for specific coastal defence systems and selected scenarios are executed

for typical focus areas. Objectives and first results of this subproject are presented.

percentage of area [%]

12

10

8

6

4

2

0

relative terrain level distribution - water board Krummhörn

-7,25

-6,75

-6,25

-5,75

-5,25

-4,75

-4,25

-3,75

-3,25

-2,75

-2,25

-1,75

-1,25

-0,75

-0,25

0,25

0,75

1,25

1,75

2,25

2,75

3,25

3,75

4,25

4,75

5,25

5,75

6,25

6,75

7,25

7,75

8,25

8,75

height [m above mean high tide]

Figures 1 and 2: Extension of flooding for one failure scenario and terrain level distribution

related to mean high tide

3 Acknowledgements

The work presented is part of the project HoRisK – C which is founded by the Federal Ministry

of Research (BMBF) under project number 03KIS080.

4 References

Burg, S.; Thorenz, F.; Blum, H. (2008): Coastal Flood Inundation Modelling for North Sea

Lowlands. Proc. Floodsite conference, Oxford.

Blum, H.; Thorenz, F. (2006): Risk Assessment for the Island of Langeoog. Die Küste Heft 70.

Boyens Verlag, Heide in Holstein, Germany.

NDG (2010): Niedersächsisches Deichgesetz i.d.F. vom 23. Februar 2004 (Nds. GVBl. S. 83)

zuletzt geändert durch Artikel 2 des Gesetzes vom 19. Februar 2010.

NLWKN (2007): Niedersächsischer Landesbetrieb für Wasserwirtschaft, Küsten- und

Naturschutz. Generalplan Küstenschutz Niedersachsen/Bremen – Festland. Norden,

Germany.

Safecoast (2008): Coastal Flood Risk and Trends for the Future in the North Sea Region.

Synthesis report. Safecoast project team, pp. 136. The Hague, The Netherlands.

Thorenz, F.; Burg, S. (2008): Risk Assessment for Coastal Lowlands in Lower Saxony. Proc.

Fourth Chinese-German Joint Symposium on Coastal and Ocean Engineering.

Darmstadt, Germany.

100

80

60

40

20

0

sum [%]


Book of Abstracts - Poster Presentation 109

Innovative shore protection for communities

Stanley J. Boc Jr.

1 Abstract

1.1 Background

The National Erosion Control Development and Demonstration Program (Section 227) was

authorized by the Water Resource and Development Act of 1996 (Public Law 104-303, 110 stat.

3658, dated October 12, 1996). The goal of the program is to foster development of innovative

and non-traditional methods of shoreline erosion control through a series of demonstration

projects. Sacred Falls State Park on the island of Oahu, Hawaii, was selected as one of the

demonstration sites to combat erosion along a section of shoreline that is threatening to

encroach upon the state highway.

1.2 Project

The innovation in shore protection at the Sacred Falls site was chosen to be an offshore reef

structure that could be constructed at a remote site with manpower utilizing off the shelf

materials and without the use of heavy equipment. Various artificial reef shapes and materials

such as, vertical lengths of high-density polyethylene (HDPE) 24 inch pipe, traffic barriers, and

large storage units were considered and tested in an undistorted linear scale of 1:16

(model:prototype) physical model. As a result of this 3-D physical model and due to the off the

shelf nature, the YODOCK traffic barrier in a three pack was found to be stable. A series of

scale model tests were conducted at an undistorted 1/16 th scale at ERDC in Vicksburg,

Mississippi during July and August of 2010 to determine wave dissipation over one to four rows

of the YODOCK three packs in 4 and 6 foot water depths with various deep water wave inputs.

All of the tests were done in a 150 ft by 3 ft flume. Deepwater waves were generated at one

end of the flume. They first encountered a 1:10 slope, which was immediately followed by a

shallower, horizontal, reef structure.

1.3 Results

As expected wave height reductions were achieved in the lee of the structure. For the 4-foot

water depth, the wave heights were reduced by 40% to 77%. For the 6-foot water depth, the

wave heights were reduced by 16.5% to 37%. The majority of the variance in the percent of

wave height reductions is attributed to the wave period and the water depth over the structure

crest. For the longer the wave periods, it was observed that the amount of wave height

reduction was reduced. The number of rows of three packs had a minimal impact on the

reduction of the wave heights.

1.4 Conclusion

Because the YODOCK traffic barrier is a popular traffic control technology many highway

departments already have these in their inventories, it can be made available for emergency

shore protection needs very quickly. This low cost and effective erosion reduction technology

has applicability in emergency and short term situations in shallow water island environments to

protect infrastructure.

2 Acknowledgements

This study was completed in the Coastal and Hydraulics Laboratory (CHL), US Army Engineer

Research and Development Center in Vicksburg, Mississippi. The author wishes to thank the

YODOCK Wall Company and Sea Engineering Inc for their valuable contributions to this project.


110 5th International Short Conference on Applied Coastal Research - SCACR 2011

3 References

Boc, S.J.; Burg, E. C. (2010): Innovative Shore Protection for Island Communities, in:

Proceedings of the 1st International Conference on Island Sustainability, pp. 209-220.

ISSN 1743-3541. Island of Brac, Croatia.


Book of Abstracts - Poster Presentation 111

The use of integrated wave-current-sediment numerical tools to

model coastal dynamics: applications in the North Adriatic Sea

Sandro Carniel 1 , Mauro Sclavo 1 and Renata Archetti 2

1 Introduction

Complex, integrated wave-current-sediment numerical models that simulate near-shore

processes need to account for wave-current interactions, turbulent mixing, wetting and drying

processes, bottom-boundary layer interactions and sediment re-suspension and transport.

These integrated numerical tools can increasingly support decision makers in the field of coastal

erosion and vulnerability (e.g. beach protection, “search and rescue” activities, support to

maritime engineering operations, etc.).

2 The Bevano case study

As an example, we present here a very high resolution application focused on the western

Adriatic coast, the Bevano river region (close by Ravenna) adopting a state-of-the-art,

integrated wave-currents-sediment numerical model. In very recent years (see Figure 1), the

original northern Bevano river mouth has been closed, and a new one has been dredged to its

south. We shortly discuss the implementation of a numerical model capable of describing the

morphological evolution of the new river mouth region as a consequence of ordinary (tidal) or

extreme (river flood, wave storms) events. The numerical model adopted is ROMS,

(www.myroms.org) in its fully 3-D, two-way coupled version with the wave model SWAN

(www.wldelft.nl/soft/swan) and a dedicated sediment transport module; the model has a

wetting/drying algorithm, accounts for wave-current interactions and adopts a sophisticated

treatment of the vertical mixing. The horizontal resolution in the order of 5 meters. To correctly

model the water flow regime inside the river, a reservoir accounting for the surface area of the

river outside of the model domain has been added to the west of the river domain. Several seatruth

campaigns carried out in the region provided the initial conditions for sediments (three

different classes have been employed) and the forcings data (sea level, river flows, wave data)

that have been then used to model the hydrodynamic and morphological conditions of the river

mouth region. Hydrodynamical and morphological conditions of the river mouth under synthetic

but realistic forcings, i.e. tidal cycle, river flooding and severe wind storms, have been

investigated.

3 Results

For brevity, we will limit our discussion here to an idealized “River flood case” (a 24-hour

triangular river flow curve, discharging 130 m 3 /s after 12 hours at its peak, was added to the

purely tidal case) and to the “Bora storm” case (using data from a severe wind and wave storm

occurred during 2009 March 9-10, and characterized by almost 24 hours of significant wave

heights around 3.5 m, period of 9 s, direction 65 degree N). Results are shown for a portion of

the domain near the inlet mouth. Figure 2a shows the sediment transport (kg/m/s) at the peak of

the river flood, with superimposed integrated velocities (max value 1.5 m/s). Note how the flow,

besides flowing through the new mouth at north, also breaks through a shallow, wettable region

in the southern area. Figure 2b shows the bottom modification (as ero/depo areas,

dimensionless) w.r.t. the initial status. Erosion or deepening of the inlet channel and deposition

of the sediment outside the inlet during the large flood event are also evident. Results for the

Bora storm simulation present max velocities � 1 m/s, a larger amount of sediments (Figure 2c)

and an increased erosion on the southern side of the inlet mouth compared to the northern side

(Figure 2d).

1 CNR-ISMAR, Castello 2737, I-30122 Venice, Italy, sandro.carniel@cnr.it

2 DICAM, University of Bologna, Italy


112 5th International Short Conference on Applied Coastal Research - SCACR 2011

4 Final considerations

Model results qualitatively agree with evidences and are now in the phase of validation against

acquired data. The application shows how it is becoming possible to provide useful support for

planning effective management of coastal areas and structures.

Figure 1: Satellite view of the Bevano river region before (left panel) and after (right panel) the

dredging of the new river mouth. The inset shows the location of the area with respect

to the Italian western coast of the Adriatic Sea.

Figure 2: (a) total transport and integrated velocities and (b) bottom modification at the peak of

the river flood event. (c) and (d): the same, but now at the peak of the Bora storm case.

5 Acknowledgements

SC acknowledges the PRIN 2008YNPNT9_005 and the FIRB RBFR08D825 Projects; MS

gratefully acknowledges the funding from the EC FP7/2007-2013 under grant agreement n°

242284 (Project FIELD_AC).

6 References

original river mouth

(a) (b)

new river mouth

August 2005 August 2008

(c) (d)

Carniel, S.; Sclavo, M.; Warner, J.C.; Tondello, M. (2007). Predicting sediment transport at

coastal structures: an integrated model approach. Proceedings of the 5 th Coastal

Structures Intern. Conf., CSt 2007, 2-4 July, Venice, Vol. II, pp. 1047-1057 (Franco,

Tomasicchio and Lamberti Eds.). DOI 10.1142/9789814282024_0092


Book of Abstracts - Poster Presentation 113

Estimate of cross-shore coastal erosion induced by extreme

waves and effects of sea level rise through ETS model

Carla Faraci 1 , Enrico Foti 2 and Rosaria E. Musumeci 3

1 Introduction

Severe storms impacting on sandy beaches may cause strong shoreline recessions, thus

increasing the vulnerability of buildings and infrastructures located in the proximity of coastal

areas.

During an actual sea storm the significant wave height changes in a very irregular manner. Due

to such a randomness, it is quite difficult to deal with natural storms and in turn to determine

their actual effects on the beach, especially when future predictions are concerned. In the

present work, the Equivalent Triangular Storm (ETS) model, introduced by Boccotti (2000), has

been adopted in order to develop an easy-to-use tool for the evaluation of the shoreline

recession, also in the light of estimating return period of cross-shore beach erosion associated

to severe storms. The effects of climate change, which may induce substantial modifications in

the nearshore wave climate and in turn in the effects of wave attacks on the coast (Olabarrieta

et al. 2007), have been also taken into account by considering the sea level rise in the next

twenty years.

2 Shoreline recession and effects of sea level rise

In order to derive the design significant wave height, Boccotti (2000) proposed the Equivalent

Triangular Storm (ETS) model, in which the actual storm is described by means of a triangle, i.e.

by means of two parameters: (i) the storm intensity a, which is equal to the maximum wave

height of the actual storm and (ii) the storm duration b, which is determined in such a way that

the maximum expected wave height is the same both for the actual and the triangular storm

(see Fig. 1a). Later on, Arena (2004) demonstrated that, dealing with ETS, the significant

parameter is the storm intensity, while the storm duration can be assumed to be equal always to

60 h without significant errors in the estimate of the return period. This assumption however

could not imply that the storm duration does not influence coastal erosion and shoreline retreat.

In order to verify such a consideration, in the present work the effects on the coasts of a single

storm event have been considered, by varying its duration within the ETS model.

Moreover it is known that coastal land loss is also related to the climate change. Indeed the

effects of climate change mainly affect coastal erosion by means of sea level change. In the

framework of the IPCC, a projection for the next hundred years estimates in about 4 mm/y the

rate of sea level rise with regional variations (Bindoff et al., 2007).

In the light of such assumptions the attack of ETS on the coast have been evaluated by means

of a simple morphological model in order to determine the beach erosion due to storms, also

due to sea level rise. In particular in the present work the model originally developed by Larson

and Kraus (1989) known as SBEACH has been applied.

In Figure 1b a reference case is shown. It reports the evolution of a cross-shore beach profile

subject to the action of an ETS characterized by a significant wave height of 4 m, a mean period

of 6.6 s, and a duration of 60 h. Two different still water levels have been considered: the first

1

Department of Civil Engineering, University of Messina, C.da di Dio 98166 S. Agata (ME) Italy,

faraci@ingegneria.unime.it

2

Department of Civil and Environmental Engineering, University of Catania, v.le A. Doria 5, 95125, Catania, Italy,

efoti@dica.unict.it

3

Department of Civil and Environmental Engineering, University of Catania, v.le A. Doria 5, 95125, Catania, Italy,

rmusume@dica.unict.it


114 5th International Short Conference on Applied Coastal Research - SCACR 2011

one, at 0 m, reproduces the present situation, the second one, 0.08 m higher, represents the

sea level rise that will occur in the next twenty years.

The picture shows that under the action of the simulated ETS the shoreline recedes of about

16.9 m when the s.w.l is at 0, while a total recession of 17.6 m, obtained as sum of coastal

retreatment and sea level rise, occurs when the s.w.l. is rised at 0.08 m, with a percentage loss

of 4%.

This procedure will also be applied to the littorals of Ragusa (Sicily), where field measurements

of cross-shore profiles have been acquired. In this framework the shoreline recession of the

case study also in the presence of coastal protection systems (e.g. beach nourishments), will be

estimated, thus allowing the return period of shoreline recession due to beach erosion during

extreme events to be determined in different scenarios, taking into account the expected sea

level rise.

Hs [m]

6

5

4

3

2

1

0

Storm i

Measured Hs-t Hs

Soglia Threshold Soglia Threshold

Inizio Storm mareggiata begins

Fine Storm mareggiata ends

ETS Mareggiata triangolare

Storm i+1

3700 3800 3900 4000 4100 4200 4300 4400

Time tempo[h] [h]

(a) (b)

Figure 1: (a) ETS identification on the basis of actual wave series; (b) Evolution of a cross-shore

beach profile with different still water levels (+0 m and +0.08m). Input ETS storm: Hs=4

m, Tm=6.6s, duration =60 h.

3 Acknowledgements

This work has been partly funded by the Italian Minister of University and Research (PRIN

2008- “strumenti operative per la stima della vulnerabilità dei litorali sabbiosi anche in presenza

di strutture costiere”).

4 References

Arena, F. (2004). On the prediction of extreme sea waves, Environmental Sciences and

Environmental Computing’, Vol II, Ch. 10 (EnviroComp Inst., Fremont, CA, USA) pp. 1-

50.

Bindoff, N.L., J. Willebrand, V. Artale, A, Cazenave, J. Gregory, S. Gulev, K. Hanawa, C. Le

Quéré, S. Levitus, Y. Nojiri, C.K. Shum, L.D. Talley and A. Unnikrishnan, (2007):

Observations: Oceanic Climate Change and Sea Level. In: Climate Change 2007: The

Physical Science Basis. Contribution of Working Group I to the IV Assessment Report of

the IPCC. Cambridge University Press.

Boccotti, P., (2000). Waves mechanics for ocean engineering. Elsevier Science.

Larson, M., Kraus, N., (1989). SBEACH: Numerical model fo simulating storm-induced beach

changes. Tech. Rep. CERC-89-9, USACE

Olabarrieta M., Medina, R., Losada, I. J., Méndez, F.J. (2007). Potential effects of climate

change on coastal structures: application to the Spanish littoral, Proc. of Coastal

Structure 2007, Venice (Italy), July 2-4.


Book of Abstracts - Poster Presentation 115

Risk management in coastal engineering – A case study in

Northern Germany

Christian Grimm 1 , Daniel Bachmann 2 and Holger Schüttrumpf 3

1 Introduction

In October 2007 the European Parliament and the Council of the European Union have adopted

the Directive 2007/60/EC on the assessment and management of flood risks. The aim of the

Directive is to reduce and manage the risk that floods pose to human health, the environment,

cultural heritage and economic activity. Within the directive the Member States of the European

Union have to carry out a preliminary risk assessment by December 2011 to identify river basins

and coastal areas which are threatened by floods. For the appointed areas flood risk maps have

to be drawn up by December 2013 and flood risk management plans focused on prevention,

protection and preparedness have to be established until December 2015. The Directive applies

to river basins as well as to coastal areas.

Within the joint KFKI (German Coastal Engineering Research Council) research project “HoRisK

– Flood Risk Management of Coastal Areas” a framework for an application-oriented risk

analysis method will be developed.

2 The Flood Risk Analysis for Coastal Areas

The aim of flood risk analysis for coastal areas is to pose a sequence of events starting with a

storm surge event, failure or non-failure events of the coastline to a flood event (FE). The

expected consequences c(FE) and the probability p(FE) of a flood event are the last link in the

chain and finally define the risk of a flood event r(FE):

r( FE)

� p(

FE)

� c(

FE).

Figure 1 shows two representative coastal areas at the German North Sea, for which the

developed approach is applicable. Figure 1 a) illustrates an area with different types of coastal

defense structures such as a dike and a second dike line with a storm surge gate. Other typical

coastal defense structures are natural grown dunes or flood protection walls. The failure

probability of the aforementioned coastal defense structures are calculated as a part of the risk

analysis.

The agricultural land use is wide spread in the coastal regions of northern Germany, shown in

Figure 1 b). Thus, agricultural damages due to a flood event of salty water are further

investigated and damage functions are derived for the analysis of consequences.

The flood risk analysis combines the determined results of probability and consequences (see

formula (1)). Three approaches to flood risk calculation can be distinguished (BACHMANN, 2011):

� The scenario-based approach applied by SAFECOAST (2008), BURZEL ET AL. (2010) or

RIJKSWATERSTAAT (2006): It focuses on pre-selected parts of the coastal defence line and

the adjacent hinterland.

� The area-based risk approach without failure applied by GIRON ET AL. (2008): The area of

investigation is a coastal area. A failure event of the defense line is excluded.

1 Institute of Hydraulic Engineering and Water Resources Management, RWTH Aachen, Mies-van-der-Rohe-Strasse 1,

52056 Aachen, Germany, grimm@iww.rwth-aachen.de

2 Institute of Hydraulic Engineering and Water Resources Management, RWTH Aachen, Mies-van-der-Rohe-Strasse 1,

52056 Aachen, Germany, bachmann@iww.rwth-aachen.de

3 Institute of Hydraulic Engineering and Water Resources Management, RWTH Aachen, Mies-van-der-Rohe-Strasse 1,

52056 Aachen, Germany, schuettrumpf@iww.rwth-aachen.de

(1)


116 5th International Short Conference on Applied Coastal Research - SCACR 2011

� The area-based risk approach applied by HALL ET AL. (2004) or SCHÜTTRUMPF ET AL.

(2009): The area of investigation is also a coastal area; failure events of the defense line

are taken into account. This approach is an enhancement of the area-based risk

approach without failure.

In the following paper the three approaches of the flood risk analysis – adopted within the

HoRisK-project – will be discussed and coast-specific characteristics are further worked out.

First preliminary results for the North Sea Island Pellworm we will be presented.

Figure 1: Representative coastal areas at the German North Sea before a storm surge

3 Acknowledgements

The joint research project “HoRisK – Flood Risk Management for Coastal Areas” is funded by

the German Coastal Engineering Research Council (KFKI) and the Federal Ministry of

Education and Research (BMBF).

4 References

Bachmann (2011): Beitrag zur Entwicklung eines Entscheidungsunterstützungssystems zur

Bewertung und Planung von Hochwasserschutzmaßnahmen. Dissertation. Aachen:

Institut für Wasserbau und Wasserwirtschaft, RWTH Aachen; (in process).

Burzel, A.; Dassanayake, D.; Naulin, M.; Kortenhaus, A.; Oumeraci, H.; Wahl, T.; Mudersbach,

C.; Jensen, J.; Gönnert, G.; Sossidi, K.; Ujeyl, G.; Pasche, E. (2010): Integrated flood

risk analysis for extreme storm surges (XtremRisK), Proc. 32nd International

Conference Coastal Engineering (ICCE), Shanghai, China.

Hall, J.; Dawson, R.; Sayers, P.; Rosu, C.; Chatterton, J. u.; Deakin, R. (2004): A methodology

for national-scale flood risk assessment. In: Water & Maritime Engineering, Vol. 156,

No. WM3, pp. 235-247. - ISSN 1472-4561.

Giron, E., Conix, I., Dewals, B., El Kahloun, M., De Smet, L. et al. (2008): ADAPT - Towards an

integrated decision tool for adaptation measures - Final report phase I

Rijkswaterstaat (2006): Flood risks and safety in the Netherlands – Full report. Rijkswaterstaat

report DWW 2006-014. ISBN 90-369-5604-9.

Safecoast (2008): COASTAL FLOOD RISK AND TRENDS FOR THE FUTURE IN THE NORTH

SEA REGION, synthesis report. Safecoast project team. The Hague, pp. 136.

Schüttrumpf, H.; Huber, N.P.; Bachmann, D.; Petry, U.; Bless, J.; Altepost, A.; Arránz Becker,

O.; Kufeld, M.; Romich, M.; Lennartz, G.; Pahlow, M.; Schumann, A.H.; Hill, P.B. (2009):

Entwicklung eines risikobasierten Entscheidungshilfesystems zur Identifikation von

Schutzmaßnahmen bei extremen Hochwasserereignissen ─ REISE ─: Abschlussbericht

zum Verbundvorhaben innerhalb der BMBF-Förderaktivität RIMAX. Aachen: Institut für

Wasserbau und Wasserwirtschaft, RWTH Aachen.


Book of Abstracts - Poster Presentation 117

On the failure mechanism and failure probability of flood

protection dunes at the German Baltic Sea coast

Angelika Gruhn 1 , Peter Fröhle 1 , Christian Schlamkow 1 , Dörte Salecker 1

1 Introduction

In 2008 the European Union approved the “Directive of the European Parliament and the

Council on the assessment and management of flood risk” (2007/60/EC). For the purpose of

reducing adverse consequences for human health, environment, commercial activity and

cultural heritage the directive aims to establish a framework for the assessment and

management of flood risk.

The Coastal Engineering Group of the University of Rostock is carrying out the research project

“HorisK-B: Loads on Coastal Protection Structures and Consequences of Failure in the area of

the Baltic Sea Coast” which is a subproject of the joint KFKI (German Coastal Engineering

Research Council) project “HoRisK – Flood risk management for coastal areas”. The project is

funded by the Federal Ministry for Education and Research and supported by KFKI (No.

03KIS079).

Objective of this project is to develop application-oriented methods and approaches for the

implementation of risk and damage analysis as a basis for the compilation of flood hazard

maps, flood risk maps and flood risk management plans. The project partners working together

on several work packages which describe the different steps in risk and damage analysis. All

steps will be applied to selected areas at the German North Sea respectively Baltic Sea. The

methodology for risk and damage analysis provides a basis for the implementation of the flood

directive for coastal areas of the German Baltic Sea Coast and the German North Sea Coast.

2 Failure mechanisms and corresponding failure probability

For the development of application-oriented damage respectively risk analysis approaches and

the determination of flood risk there is the necessity of knowing the relevant failure mechanisms

of different flood protection structures and their corresponding failure probability, i.e. probability

of occurrence of the relevant failure mechanisms.

Within the investigations the focus is on the failure mechanisms and failure probabilities of flood

protection dunes, which are typical protection structures at the German Baltic Sea Coast.

Such flood protection dunes are designed for extreme storm events. Nevertheless, these dunes

may be eroded by particular heave storm surges or be pre-damaged by such events. Basically

there are three failure mechanisms for dunes: (i) wave impact, (ii) wave overtopping and (iii)

overflow. Different factors have an influencing effect on the erosion process. The most

important factors are the water level, wave height and wave period of the impacting waves.

Furthermore, wave incident angle, grain diameter and profile gradient have an influencing effect

on the dune erosion process. Also storm characteristics (e.g. wind speed, duration of storm)

play a role. [Van Rijn]

Once the relevant failure mechanisms are determined, the corresponding failure probabilities

can be calculated by means of reliability analysis. These calculations are based on a so-called

limit state equation which compares the strength and the loading by means of process models

for a certain failure mechanism:

Z = R - S (1)

1 University of Rostock, Institute of Environmental Engineering, Coastal Engineering Group, Justus-von-Liebig Weg 6,

LAG II, 18059 Rostock, Germany, angelika.gruhn@..., peter.froehle @..., christian.schlamkow@...,

doerte.salecker@uni-rostock.de


118 5th International Short Conference on Applied Coastal Research - SCACR 2011

With: Z = Limit state equation [-]

R = Strength of the flood protection structure [-]

S = Loads on the flood protection structure [-]

The structure fails if the loading exceeds the strength of the structure, i.e. S>R. The limit state

equation becomes negative. So the failure probability corresponds to the probability of a

negative limit state equation:

{Pf} = {P (Z


Book of Abstracts - Poster Presentation 119

Wavve

and ccurrent

in nteractioon

– Com mparison of physiical

mod del

testts

with numerica

al simulattions

Stefaanie

Lorke

Jents

1 , SSarah

Horste

sje W. van deer

Meer 3

en 1 , Antje Boornschein

2 , Reinhard R Poh hl 2 , Holger Scchüttrumpf

1 ,

1

Differrent

types of

structures like smooth sloped dike es are built worldwide w too

protect adj jacent

areass

from river fflooding

or coastal c floodiing

during hi igh water lev vels. The creest

height of these

structtures

is mosttly

determine ed by a desiggn

water leve el, wave run-up

and/or waave

overtopp ping.

The iincoming

waave

paramete ers at the dike

toe relev

and llevees

are ggenerated

in n wide riverss

from a loc

curreent

mostly paarallel

to the structure s at hhigh

water le

effectt

of tidal andd

storm induc ced currentss

can be sign

curreent

on wave run-up and wave overto topping are t

FlowDDike-D,

whicch

is funded by the BMBBF

too hhigh

and exppensive

struc ctures or in t

the risk

of floodingg.

Within

this reseaarch

project experimenta

wavee

basin of DHHI

(Denmark k) for a simp

river, estuarine and

coastal dikes. d Figure

slopeed

dike. Thee

wave gene erator gener

againnst

the current,

which flows

from left

(20100).

5 vant for crest t level design

of coastal

cal wind field d and influeenced

by a s

evels. In estu uaries and along

the coas

nificant. Ther refore, the eeffects

of win

the main mo otivation for the KFKI

. The lack k of knowledg ge in this fie

too low flood d protection structures a

al investigatio ons were pe erformed in t

ple 1:3 slope ed dike and a 1:6 slope

e 1 shows the

top view of o the model

rates waves also with oblique o wave

to right. A more m detailed d description

4 dikes

strong

st, the

nd and

-p project

eld results eit ther in

and an increa ase of

the shallow water

ed dike, typic cal for

set-up for th he 1:3

e attack with

and

n is given in Lorke

2

The mmodel

tests wwere

perform med with andd

without a current c parall lel to the dikke.

Since the wave

propaagation

is diffferent

in flow wing water aand

in still wa ater, it is required

to inteerpret

the following

1 Institu

ute of Hydraulicc

Engineering an nd Water Resouurces

Managem ment, RWTH Aachen,

Kreuzherrrenstraße

7, 52 2056

Aachhen,

Germany, lorke@iww.rwth-aachen.de,

hoorsten@iww.rwth

h-aachen.de, sc chuettrumpf@iwww.rwth-aachen.de

2 Institu

ute of Hydraulicc

Engineering an nd Applied Hydrromechanics,

TU T Dresden, ant tje.bornschein@@tu-dresden.de,

Reinhard.Pohl@tu-ddresden.de

3

Van dder

Meer Consuulting

B.V;. P.O. . Box 423, 84400

AK Heerenvee en, The Netherla ands; jm@vanddermeerconsulting.nl

4 KFKI

5 BMB

Introducction

Figure 1:

Model setup – 1:3 sloped ddike

(modificat tion Lorke, 201 10)

Wave and

current

interactiion

-GCERC - Germman

Coastal En ngineering Reseearch

Council, Wedeler W Landstr raße 157, 225599

Hamburg, Ge ermany

F - Federal Ministry

of Educatio on and Researcch,

Heinemanns str. 2, 53175 Bonn,

Germany


120 5th International Short Conference on Applied Coastal Research - SCACR 2011

resultts

with respeect

to the int teraction of wwaves

and current c (Trelo oar, 1986). TTwo

main as spects

have to be considdered

while in nterpreting thhe

results:

� current

induced shoaling

conssidered

by ab bsolute and relative r wavee

parameters s

� current

induced wave w refractioon

considere ed by energy propagationn

The wwave

propaggation

path can c be divideed

into two parts. p The firs st part reachhes

from the wave

generator

to the ddike

toe. The e second part rt extends fro om the dike to oe to the dikee

crest.

If a wwave

propagates

on a cu urrent, a disttinction

has to t be made between b relaative

and absolute

wavee

parameterss.

The relativ ve wave celeerity

is the celerity c relativ ve to an obsserver

who moves m

with tthe

current, while the ab bsolute celerrity

is defined d as the cele erity comparred

to a stationary

obserrver

and the

ground, respectively.

r . According to Hedges (1987), Tre reloar (1986)

and

Holthhuijsen

(20077)

waves act only with theeir

relative pa arameters.

To clarify

the influuence

of cur rrent on wavve

parameter rs the numer rical model SSWAN

(Simu ulating

Wavees

Nearshoree)

will be use ed and can bbe

calibrated d using the results

of thee

project. SW WAN is

a thirrd-generationn

wave model

for obtainning

realistic estimates of o wave paraameters

in coastal

areass,

lakes andd

estuaries from given wind, bottom m and curre ent conditionns.

A comparison

betweeen

the resuults

of the physical p moddel

tests and d the results s of the nummerical

mode el and

thereefore

an amplification

of th he data basee

will be pres sented in the paper.

3

The iinfluence

of the current on o the anglee

of wave en nergy is given

in figure 22.

On the abs scissa

the cuurrent

paralleel

to the dike e line vx againnst

the wave e celerity c fo or shallow waater

is plotted d. The

ordinate

shows the angles of wave atttack

(dashed

line) and the angless

of wave energy e

(continuous

line), , which result

from the ssuperposition

n of current and wave ggroup

velocity y plus

the angle

of obliqque

wave approach.

The graphs show w different angles a of wavve

attack wit th and

againnst

the currrent.

For all angles of wave attac ck the angle e of wave energy incr reases

signifficantly

durinng

the dimens sionless currrents

up to 1.

For dimens sionless curre rents higher than t 2

the changes

in thhe

angle of wave w energy are lower an nd converge against 90° which corres spond

to thee

direction oof

the current

parallel too

the dike line. l For neg gative anglees

of wave attack

(against

the curreent)

the chan nging of the angle of wa ave energy is s more signiificant

than for f the

positiive

angles oof

wave atta ack (with thhe

current). In the Flow wDike-D-projeect

dimensio onless

curreents

up to vx/cc

= 0.2 were investigatedd.

4

Resultss

Figure 2:

Referennces

Angle of wave e attack β andd

angle of wav ve energy βe against a the dimmensionless

current c

for different angles

of wavee

attack, Tabs = 1.5 s

Hedgges,

T. S. (11987):

Comb binations of waves and currents: an n introductionn.

Proceedin ngs of

Institutionn

of Civil Engineers

82, ppp.

567-585.

Holthhuijsen,

L. H. (2007): Wav ves in oceannic

and coast tal waters. Ca ambridge Unniv.

Press. U.

K.

Lorkee,

S., Brüningg,

A.; Bornsc chein, A.; Gillli,

S.; Pohl, R.; Spano, M.; M van der MMeer,

J.; Werk,

S.;

Schüttrummpf,

H. (2010 0); On the eeffect

of wind

and current

on wave run-up and wave

overtoppinng;

32nd Inte ernational Coonference

on n Coastal Engineering.

SShanghai

Trelooar,

P.D. 19886:

Spectral wave refracttion

under th he influence of depth andd

current. Coastal

Engineering

9. pp. 439 9-452. Amsteerdam,

The Netherlands.


Book of Abstracts - Poster Presentation 121

Opportunities and threats along Iranian coastlines

Bahare Majdi 1 , Freydoon Vafai 2 , S. Mohammad Hossein Jazayeri Shoushtari 3 and Alireza

Kebriaee 4

1 Introduction

In this report, the strengths, weaknesses, opportunities, and threats (SWOT) framework was

used to categorize and evaluate significant marine physical parameters (or internal factors) and

human and development activities (or external factors) to achieve a shoreline management plan

for future coastal zone developments. In the SWOT framework, internal factors consist of

strengths and weaknesses and external factors consist of opportunities and threats. In this

approach an analysis of internal factors is first completed through consideration of

environmental quality (strengths) and vulnerability (weaknesses) among marine physical

indicators. Then, an external analysis is made considering the relation between human

activities and natural environment to determine threats and opportunities which may vary

depending on the activity under consideration.

2 Opportunities and Threats

Internal factors considered in this study are beach/bottom material, storm surge levels, extreme

wave height, hazard zone (flooding + erosion) extent, tsunamis, rip currents, water level

fluctuations, ground water level, river flood, erosion, accretion, seismic fault, landform and

vegetation or plant coverage.

Five types of human activity (development) were considered: 1) recreational and tourism, 2)

commercial and industrial, 3) fishery and aquaculture, 4) agricultural, and 5) residential. The

factors were weighted from 1 to 4 depending on their level of risk or advantageousness to each

activity. For each activity, weight is multiplied by score and summed up over relevant internal

factors and then averaged to arrive at the total score:

N Ai

Bi

Total Score � � (1)

i�1

N

Where Ai is the intensity of internal factor i, Bi is the weight of that factor and N is the number of

internal factors relevant to that human activity. Based on the above calculations, opportunities

and threats maps were prepared for each type of development and individual maps were

provided for each littoral cell.

1 Energy Industries Engineering & Design (EIED), No.4, Second Koohestan St., Passdaran Ave, Tehran, Iran, majdi-

b@eied.com

2 Civil Engineering Department K.N.Toosi University of Technology, No. 1346, Vali-Asr St., P.C. 19697, Tehran, Iran

fvafai@kntu.ac.ir

3 Formerly, Graduate Student K. N. Toosi Univ. of Tech., No. 1346, Vali-Asr St., P.C. 19697, Tehran, Iran,

mh_jazayeri@sina.kntu.ac.ir

4 General Directorate of Coast and Port Engineering, Ports and Maritime Organization, Tehran, Iran, kebriaee@pmo.ir


122 5th International Short Conference on Applied Coastal Research - SCACR 2011

Human

Activity

Marine

Physical

Factors

Beach / Bottom Material

Sand

Cobbles

Bedrock

Fine

Table 1: Marine physical parameters and their relation to opportunities and threats

Actual Values

Intensity Score

Yes 1

No 0

Yes 1

No 0

Yes 1

No 0

Yes 1

No 0

Recreational/

Tourism

Commercial/

Industrial

Cost

Increas

e

Cost

Increas

e

Threats Opportunities

Fishery/

Aquaculture

Cost

Increas

e

Cost

Increas

e

Agriculture

Residential

Recreational/

Tourism

Commercial/

Industrial

Fishery/

Aquaculture

Natural Pro Natural Pro Natural Pro

Water

Quality

Improveme

Weight Coefficients for Threats

1 2 3 4

Weight Coefficients for Opportunities

1 2 3 4

Water

Quality

Water

Quality

Agriculture

Natural

Protectio

n

Residential

Natural

Protectio

n

Improveme Improveme

nt nt nt

Water Water

Quality Quality

Improveme Improveme

nt nt

Natural Natural

Protectio Protectio

n n

Natural Natural Natural

Protection Protection Protection

Natural Natural

Water Water Water Protectio Protectio

Quality Quality Quality n n

Improveme Improveme Improveme

nt nt nt

Natural

Protection

Natural

Protection

Natural Natural

Natural

Protectio Protectio

Protection

n n

3 Conclusion

Regarding residential development threats maps it is recommended that any residential

development should be limited to beyond (landward side) of the Hazard Line. In this case, some

of the threats such as storm surge will no longer be applicable.

4 References

Report of Second Part of Integrated Coastal Zone Management Studies, ICZM, 2008, Shoreline

Management Plan (SMP) Studies. Criteria for Shoreline Management Plan Report.

Jahad Water and Energy Research Co.(JWERC)


Book of Abstracts - Poster Presentation 123

Modelling of surf zone turbulence and undertow with the SPH

numerical method

Christos Makris 1 , Constantine Memos 2 and Yannis Krestenitis 3

1 Introduction

Near-shore wave propagation, shoaling and depth related breaking are three of the most

significant processes concerning coastal engineers and scientists. Especially wave breaking

and the resulting turbulence in the surf zone have been studied considerably both physically

and numerically, throughout the last decades. However the hydrodynamics involved in the

description of relevant flow regimes is far from completely understood, due to their extremely

violent nature. Therefore, new, more elaborate, detail-providing computational approaches have

become necessary nowadays in assessing important surf/swash zone characteristics.

2 Aim of Study

The prime goal of the present study is the exact simulation of the highly nonlinear process of

plunging wave breaking on plane and relatively mild impermeable slopes. In the long run, we

aim at precisely quantifying the undertow, Stokes drift, set-up and run-up on sloping beaches.

Moreover, a detailed description of the turbulent features inside the surf and swash zones is

pursued. All of the above are attempted by means of one of the most ingenuous modern

numerical methods for the simulation of hydrodynamic free-surface flows, called Smoothed

Particle Hydrodynamics (SPH), as described by Monaghan (2005). Conclusively, the verification

of the capability, of the various implementations of the SPH method, to predict the details of the

entire wave breaking process ensues as a major goal of our research.

3 Methodology

SPH is a mesh-free particle method, implementing Lagrange type approximation for the Navier-

Stokes equations, through integral interpolation smoothing functions. Its Lagrangian nature

allows the unhindered simulation of free-surface flows with strong deformations, such as wave

breaking in coastal areas, as thoroughly described by Dalrymple & Rogers (2006). In this

framework the academic ‘open source’ numerical code SPHysics is used, which has been

developed by several researchers around the world with its origin at JHU (Baltimore, USA).

4 Results and Discussion

Following Makris et al. (2009), SPHysics numerical results are being compared against those of

one of the most recent comprehensive laboratory experimental studies on near-shore breaking

waves and consequent turbulence transport under them (Stansby & Feng, 2005). Calibration of

the various parameters of the SPHysics code is being attempted and its key features are

evinced through inter-comparisons of wave heights, as well as other parameters by several

numerical implementations (Fig.1, upper). Spatial discretization discerns as the most crucial

factor in forming plausible results and an effort including extremely time-consuming simulations,

with a new ‘parallel’ version of the code, towards 2 million particles is currently undertaken. In

Fig.1 (lower) somewhat plausible results concerning the time-averaged vertical distribution of

1 Aristotle University of Thessaloniki, Lab. of Maritime Engineering & Maritime Works, Div. of Hydraulics &

Environmental Engineering, Dept. of Civil Engineering, Faculty of Engineering, A.U.Th., GR-54124, Thessaloniki,

Greece, cmakris@civil.auth.gr

2 National Technical University of Athens, School of Civil Engineering, Laboratory of Harbour Works, N.T.U.A., Heroon

Polytechniou 5, GR-15780, Zografos, Athens, Greece, memos@hydro.ntua.gr

3 Aristotle University of Thessaloniki, Lab. of Maritime Engineering & Maritime Works, Div. of Hydraulics &

Environmental Engineering, Dept. of Civil Engineering, Faculty of Engineering, A.U.Th., GR-54124, Thessaloniki,

Greece, ynkrest@civil.auth.gr


124 5th International Short Conference on Applied Coastal Research - SCACR 2011

velocity vectors at various gauges covering the whole surf zone is presented, clearly

discriminating the undertow and Stokes drift regions, albeit the free-surface elevation envelopes

appear downgraded. Some light is also shed upon the inherent limitations of the non-dynamic

Smagorinsky-type model used, through the turbulent velocities spectra (Fig.2), which either

confirm or dispute the turbulence log-log scaling laws, for low or high frequencies, respectively.

Wave Height H (m)

0.18

0.16

0.14

0.12

0.10

0.08

0.06

Hexp H_x

0.04

0 1 2 3 4 5 6 7 8

Horizontal Distance, x (m)

Hexp H_a H_b6 H_b7

0 1 2 3 4 5 6 7 8

Horizontal Distance x (m)

Figure 1: (Upper) Wave height distributions between experiments (exp) and characteristic

simulation test cases (left graph: finer spatial discretization). (Lower) Time-averaged

vertical distribution of velocity vectors at various gauges covering the whole surf zone.

Velocity Power Spectrum, P(f) (m 2 /sec 3 )

1.E+05

1.E+00

1.E-05

1.E-10

1.E-02 1.E-01 1.E+00 1.E+01 1.E+02 1.E+03

Frequency, f (Hz)

Velocity Power Spectrum, P(f) (m 2 /sec 3 )

1.E+05

1.E+00

1.E-05

1.E-10

1.E-02 1.E-01 1.E+00 1.E+01 1.E+02 1.E+03

Frequency, f (Hz)

Figure 2: Horizontal (left) and vertical (right) velocity spectra for initial breaking, at still surface

level compared with isotropic inertial sub-range turbulence (full line) and 2D frozen

turbulence (dashed line), –5/3 & –3 log-log gradients respectively.

5 References

Dalrymple R. A.; Rogers B. D. (2006): Numerical modeling of water waves with the SPH

method. In: Coastal Engineering, Vol. 53, pp. 141–147.

Makris C. V.; Memos C. D.; Krestenitis Y. N. (2009): Numerical simulation of near–shore wave

breaking using SPH method, in: Proceedings of the 4th SCACR, – International Short

Conference on Applied Coastal Research. ISBN 978-3-00-030141-4. Barcelona, Spain.

Monaghan, J. J. (2005): Smoothed particle hydrodynamics. In: Rep. Prog. Phys., Vol. 68, pp.

1703–1759.

Stansby P. K.; Feng T. (2005): Kinematics and depth–integrated terms in surf zone waves from

laboratory measurement. In: J. Fluid Mech., Vol. 529, pp. 279-310.


Book of Abstracts - Poster Presentation 125

Impact of the dredging process on the granulometry of a shelly

sand. Case study of TAPARURA project, Sfax, Tunisia

Samir Medhioub 1 , Abir Baklouti 2 and Chokri Yaich 3

1 Context of the study

The material used for the land reclamation of Taparura project (420 ha) located at the northern

coastline of Sfax city-Tunisia (Fig.1) is a shelly sand material (carbon content higher than 99%)

dredged from an offshore borrow site located at Kerkennah channel. This sand was tested by

the engineering firms SCET-Tunisie and NEDECO in 1994 in the laboratories of Delft Hydraulics

in The Netherlands in order to determine the change of the grain size characteristics after

passing through a pumping system. In fact, it was necessary to know to which extent the shelly

sand grains break up after undergoing the whole dredging process. This would allow the

prediction of the actual grain size (D50) of the final fill material which in turn is used to compute

the long-shore sediment transport of the northern coastline.

At that time, the conducted tests confirmed the influence of the pumping operations and a clear

wear of the particles was noticed. The global particles reduction was then estimated at around

35%. This value was considered by SCET-Tunisie and NEDECO to be overestimated and the

final adopted value for the grain size reduction was assumed to be 10% only. Our present study

takes the opportunity of the ongoing project and the possibility to collect some realistic data at

the different stages of the dredging process in order to check the consistency of this

assumption.

Figure 1: Location of Taparura project

2 Sediment sampling campaigns

We carried out three sediment sampling campaigns on the 6th, 11th and 13th March 2008.

Table 1. Samples were generally taken according to the systematic grid using a simple perch

every meter and over a depth of 3 m, which corresponds to approximately the half of the

1 High institute of technological studies, Sfax, BP46, Sfax, 3041, Tunisia, samir.medhioub@gmail.com

2 National Engineering School of Sfax, Route de la Soukra km 4, 3038 Sfax, Tunisia , abboura.baklouti@gmail.com

3 National Engineering School of Sfax, Route de la Soukra km 4, 3038 Sfax, Tunisia , chokri.yaich@enis.rnu.tn


126 5th International Short Conference on Applied Coastal Research - SCACR 2011

hopper. In the fill area, sediments samples were also taken according to a regular grid at the

surface and at a depth of 50 cm.

At the marine borrow site of Canal Kerkennah, an investigation was carried out by the

consortium of contractors JES in charge of the execution of the Taparura project (2006-2009).

Among the whole set of the available sieve analysis, only 41 were considered in our study.

These were chosen in such a way that the location of the corresponding samples coincides with

the dredger tracks of the three campaigns.

Table 1: Details of the sediment sampling campaigns

Campaign Date Location

Number

of

samples

Depth of

sampling

(m)

Represented

area (m 2 )

Campaign

1 06/03/2008 Dredger 20 0 ; 1 ; 2 ; 3 -

On site 10 0 2600

Campaign

2 11/03/2008 Dredger 10 0 ; 1 ; 2 ; 3 -

On site 20 0 ; 0.50 1200

Campaign

3 13/03/2008 Dredger 20 0 ; 1 ; 2 ; 3 -

On site 20 0 ; 0.50 1300

3 Results: behavior of the shelly sand

The superposition of the curves of the mean sand size distribution from the granular spindle

method for the three campaign’s shows an overall increase of the sand grain size during its

journey from the borrow site to reclamation site through the dredger. At the same time, it shows

a reduction of the finer particles percentage against an increase of the coarser particles

percentage. In particular, the mean sand size D50 at the site reclamation went up to around

86% against 262% for the D90 compared to their initial values at the borrow site.

These figures can be explained by the loss of fine particles which returned to sea through the

dredger overflow and during pumping the water-sand mixture at the reclamation site. The

reduction of around 40% of the finer sand size D10 can be explained by the effect of turbulent

journey of the sand particles through the powerful pumps and other equipments of the dredger.

4 Acknowledgements

This work is undertaken as part of a research project funded by the SEACNVS (Société des

Etudes et de l'Aménagement des Côtes Nord de la Ville de Sfax). Helpful contributions have

been supplied by the TAPARURA project works contractor JES.Their help is gratefully

acknowledged.

5 References

CUR (Centre of civil Engineering Research , codes and specifications) (1987). Report 130:

Manual on Artificial Beach Nourishment., Rijkswaterstaat & Delft Hydraulics, The

Netherlands.

JES (Consortium Jan De Nul & Envisan & Somatra)(2006). Report « Recherches

géotechniques additionnelles dans la zone d’emprunt du Canal Kerkennah »,

SCET-Tunisie & NEDECO (1994),. ’Etudes d’avant-projet détaillé et élaboration du DAO pour

l’exécution des travaux de dragage et de remblaiement nécessaires au projet Taparura

à Sfax. Volume III : étude morphologique’


Book of Abstracts - Poster Presentation 127

Effect of wave overtopping on dune overwash and dune

breaching

Lydia Nagler 1 , Giuseppe Roberto Tomasicchio 2 , Iván Cáceres 3 , Felice D’Alessandro 2 ,

C. Juana E. M. Fortes 4 , Michael James 5 , Suzana Ilic 5 , Agustín Sanchez-Arcilla 3 , Francisco

Sancho and Holger Schüttrumpf 6

1 Introduction

Severe storm surges like in the Netherlands in 1953 or in Germany in 1962 caused a lot of

damage and fatalities. One reason for these dramatic consequences is the failure of coastal

protection measures due to wave loads and high storm surge water levels. Amongst others,

dunes are an important coastal protection measure which can be found on the west-, east- and

north Frisian islands.

To analyze the relevant failure mechanisms of dune breaching due to wave overtopping, large

scale physical model tests were performed in the EU-Hydralab-Project ‘Beach overwash and

Breaching’ (BOB) at UPC Barcelona in the LIM-Flume.

2 Physical Model Setup and Test Program

A sand-dune was built in the large scale LIM-Flume by using a cross-shore profile based on a

selected dune beach named ‘Canto do Marco’ which is located north of Frigueira da Foz in

Portugal. In order to expose the dune to different storm conditions, the water depth, the wave

height and the wave period were varied during the model tests. To analyze the failure

mechanisms of dune breaching due to wave overtopping, the variation of the dune profile, the

average overtopping rate, the flow depth and the flow velocity of the incoming wave and wave

overtopping were recorded by a number of measuring devices. Figure 1 shows the dune retreat

after one typical test was performed.

Figure 1: Dune retreat after storm impact

1 NLWKN Norden, Germany, Lydia.Nagler@nlwkn-nor.niedersachsen.de

2 Università del Salento, Italy, roberto.tomasicchio@unisalento.it - felice.dalessandro@unisalento.it

3 Universitat Politècnica de Catalunya, Spain, i.caceres@upc.edu - jose.alsina@ubc.edu - agustin.arcilla@upc.edu

4 Laboratorio Nacional de Engenharia Civil, Portugal, jfortes@lnec.pt - fsancho@lnec.pt - l.pinheiro@lnec.pt

5 Lancaster University, UK, s.ilic@lancaster.ac.uk - m.james@lancaster.ac.uk - b.shaw1@lancaster.ac.uk

6 RWTH Aachen University, Germany, schuettrumpf@iww.rwth-aachen.de


128 5th International Short Conference on Applied Coastal Research - SCACR 2011

3 Analysis of the measured data

The average wave overtopping rate was recorded and analyzed to determine the variation of

the average overtopping rate due to changes of the due profile. Therefore, the following

overtopping formula from the European Overtopping Manual has been applied, adapted and

used for comparison purposes:

g

q


a



RC

� b ��

m�1,

0 � exp � b

tan�


� � m 1,

0 � H m0

��

b ��

f ��

3

� H m0



� � �

With: q/(gH³m0) 1/2 dimensionless overtopping discharge [-]

q average overtopping discharge per meter structure width [(m³/s)/m]

g acceleration due to gravity (= 9.81) [m/s²]

Hm0 significant wave height from spectral analysis [m]

Rc/Hm0 relative crest freeboard [-]

Rc crest freeboard of structure [m]

tan(α) dike/dune slope [-]

ξm-1,0 breaker parameter [-]

γb influence factor for a berm [-]

γf influence factor for roughness elements on a slope [-]

γβ influence factor for oblique wave attack [-]

γν correction factor for a vertical wall on the slope [-]

4 Results

The analysis of the measured data reveal a correlation between the dimensionless overtopping

discharge q/(gH³m0) 1/2

and the dimensionless freeboard of the dune Rc/Hm0. Furthermore the

adapted overtopping formula for dikes according to the EurOtopManual (2007) shows a good

correlation to the results of the new model tests. In addition two main differences between

dunes and dikes can be observed. First, dunes have a smaller overtopping discharge for the

same freeboard height and second, the inundation of dunes occurs only at small freeboard

heights. For high freeboards, waves are eroding the seaward profile and no wave overtopping

occurs.

5 Reference

Eurotop-Manual (2007): Wave Overtopping of Sea Defences and Related Structures:

Assessment Manual, ‘Die Küste Heft 73 Jahr 2007’, Hamburg.





(1)


Book of Abstracts - Poster Presentation 129

Physical modelling of wave propagation and wave breaking in a

wave channel

Neves, D.R.C.B. 1 , Endres, L. 2 , Fortes, C.J.E.M. 3 and Okamoto T. 4

1 Introduction

Wave breaking is the most important event in the nearshore region because the energy exerted

from the breaking wave is the cause of several nearshore issues, such as set-up/down,

longshore current, nearshore circulation and so on. Authors conducted wave tank experiments

on a bottom profile constituted with different bottom slopes for the investigation of the wave

characteristics on wave breaking and especially its termination. The experimented wave

conditions represent a combination of wave periods: 1.1, 1.5, 2.0 and 2.5 s with wave heights of

12, 14, 16 and 18 cm. Free surface elevations and particle velocities were measured along the

whole channel. Also measurements of the velocity profiles were carried out in defined locations

of the studied channel.

This paper presents the experimental conditions, with the channel description, the incident wave

conditions and the experimental procedures. Furthermore, results are presented for the freesurface

elevation, wave heights, and particle velocities at the horizontal and vertical axes under

the free surface. Time, spectral and statistical of data was performed. Moreover, a more deeply

data analysis was made resulting in the calculation of several parameters, such as: (i) relative

wave height (H/d) along the channel; (ii) wave celerity; (iii) two-dimensional distributions of the

velocity components in the xy, xz and yz planes; (iv) location of the surf zone; (v) the Relative

Trough Froude Number (RTFN) (Okamoto and Basco, 2006).

2 Experimental Settings

Wave tank experiments were conducted at the LNEC. The wave flume has 32m long from the

wave maker till the end of the flume, and simplified bar-trough profile beaches was constructed

as shown in Figure 1. Slope angle of the front face of the bar and the beach section was

fixed with 1:20 and the slope of the lee side of the bar was of 1:80.

Figure 1: Wave Channel – Bottom profile

The total set of experiments was divided in three phases: (i) Firstly, surface displacements were

measured along the channel with an 8 gauge mobile structure. (ii) secondly, particle velocity

measurements with an Acoustic Doppler Velocimeter (ADV) located at the middle of the water

column were performed along the whole channel (iii) finally, velocity profiles with the ADV at

some locations were made.

1

National Laboratory of Civil Engineering, Av. do Brasil 101, Lisbon, 1700-066, Portugal, dneves@lnec.pt

2

Universidade Federal do Rio Grande do Sul, Av. Bento Gonçalves 9500, Porto Alegre, 91501-970, Brasil,

endres@ufrgs.br

3

National Laboratory of Civil Engineering, Av. do Brasil 101, Lisbon, 1700-066, Portugal, jfortes@lnec.pt

4

Hiroshima University, 1-5-1 Kagamiyama, Higashi-Hiroshima, Hiroshima, 739-8529, Japan, tokamoto@hiroshimau.ac.jp


130 5th International Short Conference on Applied Coastal Research - SCACR 2011

3 Results

For each incident wave condition, time, spectral and statistical analysis of the time series of the

free surface elevation and the velocities were obtained (Neves et al. 2010). Thus, allowed the

the calculation of the maximum, significant and average wave heights, significant and average

wave as well as the maximum, minimum and average of the velocities for each record, Figure

2a. Corresponding spectral analysis was carried out to analyze the nonlinear phenomena of

harmonic generation. For certain wave parameters, a statistical analysis was performed to

calculate standard deviation, skewness and kurtosis.

Other analysis were also performed: a) the relative wave height evolution along the channel, for

all the 15 incident wave conditions, Figure 2b, or the wave celerity; b) the two-dimensional

distributions of the velocity components in the xy, xz and yz planes, along the channel, Figure

2c; c) the RTFN index, Okamoto and Basco (2006), using wave celerity and the velocity at the

wave trough. Results are compared to find the index behavior during the wave breaking, for

different wave conditions.

b)

Hr (Hs/depth)

a)

Depth (cm)

Particle velocity (cm/s)

‐60 ‐40 ‐20 0 20 40 60 80

0

Relative wave height evolution along the bottom

1.2

1

0.8

0.6

0.4

0.2

0

Velocity vs Depth (x=‐150)

‐1 ‐0.8 ‐0.6 ‐0.4 ‐0.2 0 0.2 0.4 0.6 0.8 1

X(normalized)

5

10

15

20

Figure 2: a) Velocity vertical profiles for incident waves of H = 12, 14, 16 e 18 cm and T = 2.0 s;

b) Relative wave height evolution along the bottom for all the incident wave conditions;

c)Typical two-dimensional distributions of the velocity components (the recorded data

cloud).

4 Acknowledgements

This study is funded by the FCT under the contracts of SFRH/BPD/20508/2004,

PTDC/ECM/73145/2006 and PTDC/ECM/67411/2006 and FCT/CAPES (Brazil) – “Building a

Base for Research and Knowledge in Coastal Engineering”.

5 References

Neves, D.; Endres, L.A.M.; Fortes, C.J.E.M.; Okamoto, T. (2010): Wave breaking analysis.

Compilation and processing of data obtained from tests on physical model. BRISA

Report 05/2010. December (in Portuguese).

Okamoto, T., Basco, D.R. (2006): The Relative Trough Froude Number for Initiation of Wave

Breaking: Theory, Experiments and Numerical Model Confirmation. Coastal

Engineering, 53, 675-690.

c)

H18T20min

H18T20med

H18T20max

H16T20min

H16T20med

H16T20max

H14T20min

H14T20med

H14T20max

H12T20min

H12T20med

H12T20max


Book of Abstracts - Poster Presentation 131

Methodology for overtopping risk evaluation in port areas.

Application to the Port of Praia da Vitória (Azores, Portugal)

Paulo Raposeiro 1 , Maria Teresa Reis 2 , Conceição Juana Fortes 2 , João Alfredo Santos 2 ,

Adriana Vieira 2 , Diogo Neves 2 , Eduardo Brito de Azevedo 3 , Anabela Simões 3 , José Carlos

Ferreira 1

1 Introduction

The length of the Portuguese coast, the severity of the sea conditions and the concentration of

population and economic activities on its coastal zone, do justify the importance of studying

wave-induced risks, and in particular overtoppping due to wave action. Indeed, emergency

situations caused by adverse sea conditions are frequent and put in danger the safety of people

and goods, with negative impacts for society, economy and natural heritage. So, a methodology

to evaluate the risk associated with the overtopping of coastal or port areas is essential for the

proper planning and management of these areas. A detailed characterization of tide levels,

currents and sea waves at a local level is essential to improve the methodologies for risk

assessment, increasing the reliability of results and enabling timely issue of alerts and the

preparation of mitigation plans.

In this paper, a methodology to evaluate the risk associated with wave overtopping in port areas

is presented. The determination of overtopping is performed by using empirical tools. Then, for

assessing the risk of overtopping on those areas, the combination of the probability of

occurrence of wave overtopping, and the consequences of that occurrence are considered.

This paper illustrates the use of this methodology on the port of Praia da Vitória in the Terceira

Island of the Azores Archipelago, considering the time period between 2009 and 2010.

2 Study area

The port of Praia da Vitória, Figure 1 – is located in the Terceira Island, the second largest of

the Azores archipelago. The port basin, which is approximately 1 km x 2 km, is protected by two

breakwaters. In the port area, there are now several measuring devices that can characterize

the sea waves in the port thus making this port a very interesting place to assess the

performance of wave propagation models. Within the scope of the CLIMAAT project, a

directional wave-buoy was installed some 4 km northeast from the port, in a region 100 m deep,

which was used to validate the methodology for wave propagation applied in this study.

Figure 1: Azores, Terceira Island and port of Praia da Vitória.

1 Universidade Nova de Lisboa – FCT/DCEA, Campus de Caparica, 2829-516, Caparica; praposeiro, jcrf@fct.unl.pt

2 LNEC, Av. do Brasil, 101, 1700-066 Lisboa, Portugal; treis, jfortes, jasantos, asvieira, dneves@lnec.pt

3 Universidade dos Açores, Campus da Terra Chã, 9701-851, Angra do Heroísmo, Portugal; Anabela, edubrito@uac.pt


132 5th International Short Conference on Applied Coastal Research - SCACR 2011

3 Methodology and Results

The methodology to evaluate the overtopping risk associated with the port of Praia da Vitória,

and especially of the study area protected by the south breakwater, is herein presented and it is

based on four main steps:

� Determination of wave overtopping over the breakwater considering the time period

between 2009 and 2010.

� Determination of the probability of overtopping exceeding pre-determined

thresholds;

� Establishment of qualitative factors related to the consequences of the occurrence

of overtopping that exceeds those thresholds;

� Combination of the above steps to assess overtopping risks.

For the determination of wave overtopping at the study area, the method described in

Raposeiro et al. (2010) will be followed for data obtained between 2009 and 2010 from a

hindcast model. These data are propagated to the port of Praia da Vitória by using numerical

models of wave propagation, included in the geographical information system (GIS), GUIOMAR

(Neves et al. 2009). Figure 2 presents the time series of significant wave heights for the points

inside the port from January 1 to December 31, 2009. Then, the determination of overtopping is

performed by using empirical tools.

Figure 2: Time series of significant wave height (HS) at several points inside the port, for the

period from January 1, 2009 to January 1, 2010. Bathymetry and location of points P1

to P4.

To determine the vulnerability and the overtopping risk at the study area, a methodology was

developed that uses a geographical information system, as well as the multi-criteria analysis, to

evaluate the vulnerability to different overtopping episodes of the various areas at risk. Three

tables were set: i) a table of probability of occurrence of an adverse event, as the wave induced

overtopping; ii) a table with the consequences of the occurrence of overtopping; and iii) based

on the two previous tables, a table of overtopping risk in the port .

4 Acknowledgements

The authors acknowledge the financial support from the Portuguese Foundation for Science

and Technology (FCT) through contracts PTDC/AMB/67450/2006, PTDC/ECM/67411/2006 and

PTDC/ECM/73145/2006.

5 References

Raposeiro, P.D.; Fortes, C.J.E.M.; Reis, M.T.; Ferreira, J.C. (2010). Development of a

methodology to evaluate the flood risk at the coastal zone. In Geographic Technologies

Applied to Marine Spatial Planning and Integrated Coastal Zone Management, Calado,

H. and Gil, A. (Eds.), August, pp. 129-137 (ISBN: 978-972-8612-64-1).

Neves, D.R.C.B; Zózimo, A.C.; Pinheiro, L.V.; Fortes, C.J.E.M. (2009) - GUIOMAR: Recent

developments and application to the port of Sines. Proc. 6ªs Portuguese Seminar of

Coastal and Port Engineering, PIANC, Funchal, October, 7-8 (in Portuguese).


Book of Abstracts - Poster Presentation 133

Rapid evolution of shoreline after a beach nourishment

downdrift of a groin and at an embayed beach: theory vs.

observation

Renata Archetti 1 , Sandro Carniel 2 , Claudia Romagnoli 3 and Mauro Sclavo 2

1 Introduction

Beach nourishments are regularly being carried out along the Italian coasts, and are very often

associated to other beach defence interventions, so that the combined use of breakwaters and

nourishment represents a new beach defence strategy. The lifetime of such nourishments can

be predicted in various ways, among which the use of empirical methods and one-line models,

developed from the Pelnard-Considére (1956) diffusion equation, which are based on simplified

hypothesis. One application of the model is the evolution of a shoreline segment updrift and

downdrift of a perpendicular barrier (Dean, 2002).

In this paper we will describe the evolving shoreline over a 3,5 years period after an important

nourishment, approx. 107 m 3 /m (Preti, 2009), made by submarine sand carried out in Lido di

Dante beach, Italy (Archetti, 2009). The focus will be made on the evolution of an embayed

beach of Lido di Dante and of the rapid evolution of the shoreline located down drift a groin.

The aim of the paper is twofold; first, to give a description of a shoreface behaviour after the

nourishment, and second, to compare the observations with the results of common one-line

evolution models, in order to give a magnitude of the uncertainties in their use, and to compare

the shoreline behaviour of the embayed beach with the adjacent beach.

2 Methods and expected results

A dataset of approximately bimonthly surveys of the shoreline was generated with the help of

the Intertidal Beach Mapper (IBM, Aarninkhof et al., 2003) analysing the ARGUS images taken

by the video monitoring station in Lido di Dante. The IBM model determines the threedimensional

beach surface between the low-tide and high-tide shoreline contours by mapping a

series of beach contours from Argus video time exposure imagery, sampled throughout a tidal

cycle. The shoreline at the 0 sea water level is then estimated by interpolation of the intertidal

beach bathymetry.

A selection of the available shorelines is plotted in Figure 1 where video surveyed shorelines

after the nourishment are presented. The sand was redistributed during the first months after

the nourishment, resulting in a more stable configuration since autumn 2007. This collection of

data represents a unique dataset of shoreline evolution in presence of structures.

Wave and sea water level data have been collected for the whole study period. Expected

results are:

1 DICAM, University of Bologna, Italy, Viale Risorgimento, 2. 40136 Bologna, Italy. renata.archetti@unibo.it

2 CNR-ISMAR, Castello 2737, I-30122 Venice, Italy sandro.carniel@cnr.it ,

3 Dipartimento di Scienze della Terra University of Bologna. claudia.romagnoli@unibo.it,


134 5th International Short Conference on Applied Coastal Research - SCACR 2011

[m]

0

100

200

300

-1200 -1000 -800 -600 -400

[m]

-200 0 200

Figure 1: Evolution shorelines after the nourishment in Lido di Dante.

070628

070925

071225

080304

080701

081209

090404

091119

100417

- The quantification of main shoreline changes, in terms of displacements of the shoreline

in the January 2007-April 2011 interval for the embayed beach and for the adjacent southern

beach;

- the analysis of storm-driven beach rotation events, in order to assess the dependence

of the beach response on the wave characteristics and provenance and the correlation of the

shoreface variability with the wave energy flux.

- the comparison of the beach evolution observations with the one line model results.

3 Acknowledgements

The research was supported by the project PRIN 2008 “Tools for the assessment of coastal

zone vulnerability related to the foreseen climate change” funded by the Italian Ministry of

University and Research (MIUR).

4 References

Dean, R. G. (2002): Beach Nourishments. Theory and Practice, Elsevier. The Netherlands.

ISBN 981-02-1547-9 p397.

Preti, (2009). Stato del litorale emiliano-romagnolo all’anno 2007 e piano decennale di gestione.

I quaderni di ARPA, Regione Emilia-Romagna, Bologna, 270 pp. In Italian.

Aarninkhof, S.G.J., I.L. Turner, T.D.T. Dronkers, M. Caljouw, and L. Nipius. (2003). A videotechnique

for mapping intertidal beach bathymetry. Coastal Engineering, 49, 275-289.

Archetti, R., (2009). Quantifying the evolution of a beach protected by low crested structures

using video monitoring. Journal of Coastal Research 25(4): 884-899.

Pelnard Considerè, R. (1956). Essai de Theorie de l’Evolution des Formes de Rivage en Plages

de Sable et de Galets. 4th Journees de l’Hydraulique. Les Energies de la Mer, Question

III. Rapport 1.


Book of Abstracts - Poster Presentation 135

Calibration and validation of an analytical model to predict

dune erosion due to wave impact and overwash

Andrea Ricca 1 , Felice D’Alessandro 2 and Giuseppe Roberto Tomasicchio 2

1 Introduction

Coastal dunes generally constitute the final protection line against high waves and water levels

during severe storms. However, storm-driven surge, wind and waves can cause significant dune

erosion with large-scale morphological changes, damages to infrastructures and loss of human

lives. Failure of dunes takes place when the rate of the erosion is so large that flooding of the

low-lying areas behind them occurs (Tomasicchio et al. 2011a; Tomasicchio et al. 2011b).

Coastal engineers are often faced with estimation of the impact on the beach-dune system of

severe storms in terms of recession distance, eroded volume and overwash rate. In the recent

years several numerical models have been developed for these purposes (e.g. C-SHORE,

Kobayashi et al. 2007; Figlus et al. 2011). As an alternative to a numerical approach, analytical

models typically require marked simplifications in the description of the governing processes,

forcing, and initial and boundary conditions, whereas numerical models can deal with these

aspects with less restrictions. However, analytical models still have their use since the simplicity

make them easy to apply, which is valuable in the preliminary stage of a project when

approximate estimates are required.

In the present paper, the analytical model by Larson et al. (2004, 2005) is calibrated and

validated against a data set derived from recent large-scale physical model experiments. The

study provides coastal engineers with a more verified tool for the preliminary estimates of dune

recession distance and eroded volume.

2 Laboratory data set

Large-scale laboratory data on dune erosion and overwash under storm conditions have been

considered in the present study to calibrate and validate the analytical model by Larson et al.

(2004, 2005). The physical model tests have been carried out at the CIEM wave flume of the

LIM/UPC in Barcelona within the EU-Hydralab III Integrated Infrastructure Initiative. A total of 9

model tests have been performed with various combinations of random wave attacks and water

depths acting on a sandy beach-dune system. The wave conditions have been selected in order

to investigate the influence of different “load parameters” (significant wave height, Hs,o, peak

wave period, Tp, wave steepness, sp, and still water level, ho) on dune recession rates and

induced dune erosion regimes (Sallanger et al. 2003). The duration of a single test has been

divided into different time-intervals, kept constant Hs,o, Tp and ho. After each interval, the test

has been interrupted to perform profile measurements along the longitudinal flume axis by

means of a mechanical profiler. Figure 1 shows an example of time evolution of the measured

beach-dune profile for the case of Test E (Hs,o = 0.33 m, Tp = 3 s).

3 Model calibration and validation

The laboratory data set has been adopted to verify the capability of the model to reproduce the

retreat of the dune face and calculate the eroded volume, ΔVE, at specific time intervals. Initially,

the analysis of the data set allowed to determine the two main parameters in the model, namely

the empirical transport coefficient, Cs, and the run-up height, R, through a least-square fit

procedure. In addition, the values of ΔVE determined by means of the C-SHORE model

1

Department for Soil Conservation, University of Calabria, Ponte P. Bucci Cubo 42 B, 87036 Arcavacata di Rende, Italy

andrearicca@hotmail.it

2

Engineering Dept., University of Salento, via Monteroni, Ecotekne, 73100 Lecce, Italy felice.dalessandro@unisalento.it;

roberto.tomasicchio@unisalento.it


136 5th International Short Conference on Applied Coastal Research - SCACR 2011

(Kobayashi et al. 2007; Figlus et al. 2011) have been considered. The agreement between the

analytical solution (Larson et al. 2004, 2005) with both the physical data and the numerical

results was satisfactory, concluding that the analytical model gives reliable quantitative

estimates of dune recession and erosion during storms, provided that the forcing conditions are

known and that the geometry of the beach-dune configuration is similar to the one assumed in

the governing equations, with a plane-sloping foreshore backed by a steep/quasi-vertical dune.

h (m)

1,00

0,50

0,00

-0,50

-1,00

-1,50

-2,00

-2,50

0 10 20 30 40 50 60

x (m)

t = 0

t = 600 s

t = 1200 s

t = 1800 s

t = 3000 s

t = 5400 s

Figure 1: An example of time evolution of the measured beach-dune profile. Test E

4 References

Figlus, J., Kobayashi, N., Gralher, C., Iranzo, V. (2011): Wave overtopping and overwash of

dunes. In: Journal of Waterway, Port, Coastal and Ocean Engineering, ASCE, 137(1),

26-33.

Kobayashi, N., Agarwal, A., and Johnson, B.D. (2007): Longshore current and sediment

transport on beaches. In: Journal of Waterway, Port, Coastal and Ocean Engineering,

ASCE, 133(4), 296-306.

Larson, M., Erikson, L., Hanson, H. (2004): An analytical model to predict dune erosion due to

wave impact. In: Coastal Engineering, Elsevier, (51) 675-696.

Larson, M., Donnelly, C., Hanson, H. (2005): Analytical modelling of dune response due to

wave impact and overwash. In: Proceedings of 5 th International Conference Coastal

Dynamics 2005, Barcelona, paper n. 90, ASCE.

Sallenger, A.H., Howd, P., Stockdon, H., Guy, K., Morgan, K.L.M. (2003): On predicting storm

induced coastal change. In: Proc. Coastal Sediments, Clearwater Beach, Florida, USA,

World Scientific.

Tomasicchio, G.R., Sanchez Arcilla, A., D’Alessandro, F., Ilic, S., James, M., Fortes, C.J.E.M.,

Sancho, F., Schüttrumpf, H. (2011a): Large-scale flume experiments on dune erosion

processes. In: Journal of Hydraulic Research, SI-Hydralab (CMH)-IAHR.

Tomasicchio, G.R., D’Alessandro, F., Fortes, C.J.E.M., Ilic, S., James, M.R., Sanchez-Arcilla,

A., Sancho, F., Schüttrumpf, H. (2011b): Dune erosion and overwash in large-scale

flume experiments. In: Proceedings of Coastal Sediments ’11, Miami, in press.

5 Acknowledgements

The present research has been supported by the European Community's Sixth Framework

Programme through the grant to the budget of the Integrated Infrastructure Initiative

HYDRALAB III within the Transnational Access Activities, Contract no. 022441.


Book of Abstracts - Poster Presentation 137

Analysis of uncertainties in coastal structure design based on

expert judgement

Holger Schüttrumpf 1

1 Introduction

Input parameters and models (in the form of limit state equations) in coastal engineering are

influenced by uncertainties. The imperfect knowledge of these parameters may result in an

underdesign and a failure of a coastal structure but may also result in an expensive overdesign.

Therefore, the uncertainties of the stochastic parameters and models should be considered for

probabilistic coastal structure design.

A working group was established by the German Committee for Coastal Structures (EAK) to

give recommendations for the consideration of uncertainties in the design of coastal structures

(e.g. seadikes, breakwaters, revetments). Objective of this working group is to (i) identify

uncertainties in coastal structure design, (ii) to quantify these uncertainties and (iii) to give

recommendations how to consider these uncertainties in the design of coastal structures. The

present paper is focusing on the quantification of uncertainties related to the input parameters of

coastal structure design. Uncertainties of the models and limit state equations can be taken

from literature. Uncertainties of the input parameters are more difficult to assess. The

specification of uncertainties related to measured parameters is possible, but in most cases

design parameters were never measured before.

The present paper summarizes the second phase of this investigation. The first phase was

based on an expert judgement using a general questionnaire without giving details on the

structure itself or the wave conditions. Results of the first questionnaire were published by

Schüttrumpf et al. (2006). The second questionnaire was set-up for three typical coastal

structures:

� Coastal seadike

� Rubble mound breakwater

� Caisson breakwater

Selected experts in coastal engineering were asked to estimate uncertainties related to

geometrical and hydraulic parameters for a given structure and given wave conditions. In

addition, a distinction in the judgement of uncertainties related to the incoming wave conditions

was made to consider the method of wave determination (field measurements, prediction from

numerical models, visual observations, etc.). The data from the questionnaires were analysed

statistically. Objective is to recommend uncertainties in the absence of more detailed

information from long term wave measurements or water level measurements.

2 Uncertainties in Coastal Structure Design

Mathematically, uncertainty is mostly defined as a relative error. By assuming a normal

distribution of a quantity x with a mean value x and a standard deviation of �x, the uncertainty is

defined by the coefficient of variation �’x:

� x � ' x �

(1)

x

Assuming a normal distribution is not always correct but by lack of sufficient data, a normal

distribution is often applied in coastal engineering.

Unfortunately, an easy determination of the standard deviation is often not possible for design

parameters in coastal engineering due to different sources of uncertainty. The coefficient of

1 Institute of Hydraulic Engineering and Water Resources Management, RWTH Aachen, Kreuzherrenstraße 7, 52056

Aachen, Germany, schuettrumpf@iww.rwth-aachen.de


138 5th International Short Conference on Applied Coastal Research - SCACR 2011

variation �Y’ of a design variable Y consists of M (statistically independent) individual

coefficients of variation �x,i’ standing for different sources of uncertainty:

M


i�1

� '� �

(2)

Y

X , i '

The main sources of uncertainty can be classified in three groups (Kortenhaus, 2003):

Model uncertainties: Model uncertainties are related to input parameters and limit state

equations which can be described by statistical functions and statistical parameters.

Uncertainties related to input parameters result from the measurement itself, from the use of

(often) inhomogeneous data, the applied statistical distribution to describe and to extrapolate

the data base. Uncertainties related to limit state equations result from the quality of the limit

state equation to describe and to consider all physical processes with regard to measured data

and the extrapolation of the limit state equations for design conditions. Model uncertainties can

be reduced by more or better data.

Inherent uncertainties: Inherent uncertainties result from the randomness of the input

parameters in space and time. Inherent uncertainties are related to the natural variation of

hydraulic and structural parameters. Thus, the effects of ageing of the structure or climate

changes are inherent uncertainties which can neither be reduced nor removed. An example is

the probability distribution describing extreme water level records which varies in time and is not

suitable to describe the maximum water level of next year.

Human Factor: Uncertainties result also from errors during the planning process, the

construction process, the monitoring or the maintenance of the structure. These “human factors”

are difficult to assess during the design process but can be of significant influence on the

structural safety.

Types of Uncertainties

Model Uncertainties Inherent Uncertainties

- Input parameter

-Limit state equations

- statistical distribution

- models

can be reduced by:

- more data

-betterdata

- Natural variability

- climate change

- Ageing of structure

- Material properties

can neither be reduced

or removed

Human Factor

- Planning

- Construction

- Monitoring

- Maintenance

can be reduced by:

- improved knowledge

- improved organisation

Figure 1: Types of Uncertainties (Kortenhaus, 2003)

These types of uncertainties must be considered during the design process of a coastal

structure. To reduce or to quantify uncertainties in coastal structure design, different methods

are used (Van Gelder, 2000):

� Data collection

� Research

� Expert judgement.

The present paper presents a new expert judgement approach. Delegates of the conference will

be ask to contribute and the new data will be used to verify the existing database.

3 References

Kortenhaus, A. (2003) Probabilistische Methoden für Nordseedeiche. Dissertation. Technical

University of Braunschweig.

Schüttrumpf, H.; Kortenhaus, A.; Peters, K. and Fröhle, P. (2006) Expert Judgement of

Uncertainties in Coastal Structure Design. Proceedings 30th Int. Conf. on Coastal

Engineering. San Diego. US

Van Gelder, P.H.A.J.M (2000) Statistical Methods for the risk-based design of civil structures.

PhD-thesis Delft University of Technology


Book of Abstracts - Poster Presentation 139

Solitary wave impact on a seawall

Ryszard Staroszczyk 1 , Maciej Paprota 1 and Wojciech Sulisz 1

The problem of a solitary wave impact on a seawall is considered. The problem is solved by

employing two methods. In the first method the problem is solved in the Lagrangean

coordinates by applying the smoothed particle hydrodynamics method (SPH), while in the

second approach the Eulerian description is applied and the problem is solved by employing the

method of eigenfunction expansions. In the SPH method (Monaghan,1992), water is treated as

an inviscid and weakly compressible liquid, for which the pressure is related to density by a

constitutive equation. The latter assumption (as opposed to the common water incompressibility

approximation) enables using an efficient explicit time-stepping scheme (of the predictorcorrector

type) for integration of the continuity and momentum equations describing the motion

of the fluid. A corrected version of the SPH method is employed, in which standard interpolation

functions (kernel smoothing functions in the SPH terminology) are modified in such a way that

so-called linear reproducing conditions (Belytschko et al., 1998) for both kernel approximations

and their gradients are satisfied. This modification is analogous to the moving least-square

(MLS) approach known from other meshless discrete methods. In the second approach used in

this work, water is treated as an incompressible fluid, and the governing equations are solved

semi-analytically by applying an eigenfunction expansion method developed by Sulisz and

Paprota (2004). The solution is based on the kinematic and dynamic free-surface boundary

conditions expanded in a Taylor series (Dean and Darlymple, 1984). The solution obtained in

the form of the eigenfunction expansions satisfies the continuity equation and the bottom

boundary condition. In order to satisfy the non-linear boundary conditions on the free surface of

water, a time-stepping procedure is applied to calculate unknown free-surface elevation and

velocity field components. The initial conditions for the displacement, velocity and pressure

fields in the fluid have been adopted in the form of the second-order analytical approximation to

the solution of the Korteweg—de Vries equation describing waves in shallow water (Wehausen

and Laitone, 1960).

The two above methods have been used to simulate numerically a solitary wave

propagation in water of uniform depth, followed by the wave impact on a vertical seawall. The

simulations focus on the determination of the maximum run-up of the wave on the wall, the

calculation of time-histories of the pressures exerted by water on the structure, and the

evaluation of the water velocities in the vicinity of the seawall. In particular, the effect of the

wave height on the behaviour of solitary waves is investigated. Two cases have been

considered. In the first case, of a smaller ratio of the incident wave height to the still water

depth, the non-linear effects are moderate, whereas in the other case, of a larger height of the

solitary wave, these effects are significant. The predictions of the two approaches, one based

on the Lagrangean, and the other on the Eulerian description, are compared to identify wave

regimes for which both methods give satisfactory results. As an illustration, the plots in Figure 1

show the evolution of the water free surface during an impact event, in the case of the solitary

wave amplitude equal to 0.3 of the water depth, h.

1 Institute of Hydro-Engineering, Polish Academy of Sciences, Koscierska 7, 80-328 Gdansk, Poland,

rstar@ibwpan.gda.pl, mapap@ibwpan.gda.pl, sulisz@ibwpan.gda.pl


140 5th International Short Conference on Applied Coastal Research - SCACR 2011

Elevation z / h

1.6

1.4

1.2

1.0

1.6

1.4

1.2

1.0

1.6

1.4

1.2

1.0

1.6

1.4

1.2

1.0

1.6

1.4

1.2

1.0

1.6

1.4

1.2

t = 0 s

t = 3 s

t = 6 s

t = 9 s

t = 12 s

t = 15 s

1.0

-15 -10 -5 0 5 10

Position x / h

References

Figure 1: Evolution of the free surface profile of a solitary wave impacting on a wall at x/h=10.

Belytschko, T.; Krongauz, Y.; Dolbow, J. and Gerlach, C. (1998): On the completeness of

meshfree particle methods. In: International Journal for Numerical Methods in

Engineering, Vol. 43, No. 5, pp. 785-819.

Dean, R.G. and Dalrymple, R.A. (1984): Water Wave Mechanics for Engineers and Scientists.

Prentice-Hall, Inc., pp. 55-61, Englewood Cliffs, USA. ISBN 0-13-946038-1.

Monaghan, J.J. (1992): Smoothed particle hydrodynamics. In: Annual Review of Astronomy and

Astrophysics, Vol. 30, pp. 543-574.

Sulisz, W. and Paprota, M. (2004): Modeling of the propagation of transient waves of moderate

steepness. In: Applied Ocean Research, Vol. 26, No. 3-4, pp. 137-146.

Wehausen, J.V. and Laitone, E.V. (1960): Surface Waves. In: Encyclopedia of Physics (Ed.

S. Flügge), Vol. IX, pp. 446-778, Springer-Verlag, Berlin.


Book of Abstracts - Poster Presentation 141

Seasonal changing sand waves and the effect of surface waves

F. Sterlini 1 , S. IJzer 2 and S.J.M.H. Hulscher 3

1 Introduction

The seabed of shallow shelf seas is rarely flat. When sediment is in good supply and tidal flows

are sufficiently strong, wavelike subaqueous sediment structures, called sand waves, can occur.

With a migration rate up to several tens of meters per year, a wave length of several hundreds

of metres and a height up to 1/3 of the local water depth, sand waves can severely affect

human offshore activities, such as navigation. This makes it important to understand the

physical processes that shape and change sand waves, in order to improve management

strategies of expensive operations such as e.g. the dredging of shipping lanes.

In field data, temporal variation in the migration and the shape of sand waves are found.

Besides other factors, surface wave action might cause this variation (Van Dijk & Kleinhans,

2005).

In this study, a morphodynamic model and field data were used to investigate the importance of

the surface waves. The used model is based on an idealized model by Németh et al. (2006) and

further developed by Van den Berg and Van Damme (2006). It is a two dimensional vertical

model, which is developed specifically to describe sand wave evolution from its generation, to

its fully grown state. For equations we refer to Van den Berg & Van Damme (2006) and Sterlini

et al. (2009).

2 Varne

Figure 1: One of the studied transects in the Varne sand wave area.

The Varne bank is located in the Dover strait near the UK. In a pre and post storm study in the

Varne area we find a lowering of the sand wave crest by a metre. When compared to the model

output, it was found that these kind of changes in crests can occur due to wave action alone.

However, the calculated timescale for these modifications (20 to 50 weeks) is too long when

compared to the length of storms in general. The morphological timescale in which the sand

1 University of Twente, Faculty of Engineering Technology, Water Engineering and Management, PO box 217, 7500 AE

Enschede, the Netherlands, F.M.Sterlini@utwente.nl.

2 Department of Waterways and Public Works, Ministry of Infrastructure and the Environment, the Netherlands.

3

University of Twente, Faculty of Engineering Technology, Water Engineering and Management, PO box 217, 7500 AE

Enschede, the Netherlands.


142 5th International Short Conference on Applied Coastal Research - SCACR 2011

waves form in the modelling results is however realistic. It was also found that the effect sorted

by wave stirring alone is limited (30 cm) with respect to the changes observed in the field (1

metre). The lowering effect in the stormy period, might be caused by more than just higher

surface waves, e.g. a combination with variations in the tidal currents. This is further supported

by the strong relation found in wave (and wind) direction and the direction of the residual tidal

flow.

3 Eco Morf 3

The Eco Morf 3 area is situated about 50 km of the Dutch coast. Bathymetry analysis show

sand waves move back and forth in the seasons. The migration is a result of a combined

wind/wave driven current and a long term mean residual flow. Model results show that the wave

direction on its own can not explain the migration direction of the sand waves. Most probably a

variable residual flow is needed. Higher surface waves increase the dynamics of the system as

higher waves lower the growth time and increase the transport rate. Sand wave volume

increases and crests are flattened and lengthened under the increased stirring action of higher

waves. The angle of the waves with respect to the current lowers the horizontal asymmetry.

4 Conclusion

In this study, a morphodynamic model and field data were used to investigate the importance of

the surface waves on sand wave migration and shape. The field observations show that periods

with high surface waves can significantly affect the sand waves. Model results indicate that the

surface waves explain this partly, and in combination with a variation in the tidal current even in

a larger extent.

Waves in the direction of the residual tide add to migration and sand transport in that direction.

Waves opposing the residual current reduce the transport and migration. The waves and

current combined have a significant effect on the dynamics of the system as higher surface

wave decrease the time in which e.g. sand wave grow and increase transport rates. Besides it

was found that an increasing angle of waves with respect to the residual current increasingly

limits sand wave migration and increases the horizontal asymmetry. The effect increases for

increasing height of surface waves.

5 Acknowledgements

This work originates from S. IJzers’ masters thesis Civil Engineering & Management, University

of Twente.The authors would like to acknowledge Ad Stolk (Rijkswaterstaat), Thaienne van Dijk

(Deltares) and Andrew Winterbottom (UK Hydrographic Office) for supplying the data.

6 References

Harris, P.T., “Sandwave movement under tidal and wind-driven currents in a shallow marine

environment: Adophus Channel, northeastern Australia”, Continental Shelf Research,

9(11):981-1002 1989

Németh, A. A., Hulscher, S. J. M. H., and Van Damme, R. M. J. (2006). Simulating offshore

sand waves. Coastal Engineering, 53, pp. 265–275.

Sterlini, F., Hulscher, S. J. H. M., and Hanes, D. M. (2009). Simulating and understanding sand

wave variation: A case study of the Golden Gate sand waves. Journal of Geophysical

Research, 114 (F02007,doi:10.1029/2008JF000999).

Van den Berg, J. and Van Damme, D. (2006). Sand wave simulations on large domains. In:

River, Coastal and Estuarine Morphodynamics:RCEM2005,Urbana, Illinois, USA, 4-7

October 2005, Parker, G. and Garcia, M. H.(eds.), pp. 991–997. Taylor & Francis.

Van Dijk, A. G. P. and Kleinhans, M. G. (2005). Processes controlling the dynamics of

compound sand waves in the North Sea, Netherlands. Journal of Geophysical Research

- Earth Surface, 110 (F04S10,doi:10.1029/2004JF000173).


Book of Abstracts - Poster Presentation 143

Analysis of tide measurements in a Sicilian harbour

Pietro Danilo Tomaselli 1 , Carlo Lo Re 2 and Giovanni Battista Ferreri 3

1 Introduction

Sea level oscillations, usually indicated as tides, are produced by superposition of many

contributions, the main ones being astronomic and meteorological. The former are persistent,

although not exactly periodic, and can be predicted with adequate precision; the latter are

contingent, depending on factors like atmospheric pressure, storms, etc., so that a statistical

approach proves to be necessary for their forecasting. In this paper, early results of examination

of tide oscillations observed during the period 1999-2009 in a harbour located on the South

coast of Sicily are reported.

2 Data set and meteorological contribution

The harbour selected for the analysis is about 100 km from a wave buoy and both are located

along the same almost rectilinear coast. The presence of the wave buoy makes it possible to

investigate the connection between the observed tide measurements, outside the usual

astronomic oscillation range, and the wave data recorded by the buoy. This study will be carried

out in further papers. Both the tide gauge and the wave buoy record data every one-hour.

For each year, the tide measurements were used to draw the astronomic tide by means of

harmonic analysis (Pawlowicz et al., 2002). By varying the number of tide components we

obtained four different one-year tide simulations. Comparative examination of the simulated

one-year tides with the ones observed in the whole period 1999-2009 led us to choose, for each

year, the simulations obtained using the 44 components that Pawlowicz et al. (2002) refer to as

astronomic. Each of these simulations was assumed as the astronomic tide of the related year.

Fig. 1 shows, as an example, the astronomic tide and the observed tide relating to the year

2005.

For each year, the difference between the observed tide and the astronomic one was imputed

to meteorological factors and indicated as “noise.” The noise proved to be both positive and

negative: it is likely that positive noise is imputable to sea storms moving onshore while

negative noise to storms moving offshore. The same figure reports the time intervals during

which the buoy recorded sea storms with a 1.5 m threshold.

3 Statistical analysis of the meteorological contribution

Since the noise was imputed to meteorological factors, it was treated by a statistical approach.

First, reporting the points on the probability plot, it was established that the noise values do not

follow the normal distribution. This is likely because the noise, if really due to meteorological

factors, should rather follow an extreme value distribution.

Therefore, the Gumbel, GEV and Weibull distributions were considered (Kotz and Nadarajah,

2001). To this aim, the positive noise (onshore storms) was divided from the negative noise

(offshore storms) and the latter considered in its absolute value, because, actually, what is

connected with the contingent meteorological situation is the noise intensity. The two

1

Dipartimento di Ingegneria Civile, Ambientale e Aerospaziale, Università degli Studi di Palermo (Dept. of Civil,

Environmental and Aerospace Engineering, University of Palermo), Italy; Viale delle Scienze, Ed. 8, I-90128 Palermo,

Italy; kobelak@libero.it.

2

Dipartimento di Ingegneria Civile, Ambientale e Aerospaziale, Università degli Studi di Palermo (Dept. of Civil,

Environmental and Aerospace Engineering, University of Palermo), Italy; Viale delle Scienze, Ed. 8, I-90128 Palermo,

Italy; lore@idra.unipa.it.

3

Dipartimento di Ingegneria Civile, Ambientale e Aerospaziale, Università degli Studi di Palermo (Dept. of Civil,

Environmental and Aerospace Engineering, University of Palermo), Italy; Viale delle Scienze, Ed. 8, I-90128 Palermo,

Italy; giofer@idra.unipa.it.


144 5th International Short Conference on Applied Coastal Research - SCACR 2011

populations of values were then treated separately.

For each population of each year, the empiric frequency curve was compared with the curves of

the three laws considered. The comparison showed that, on the whole, both the positive and

negative noises follow the Weibull distribution more closely than the other two. The Weibull

distribution was therefore assumed as the noise distribution.

Finally, a good fit of the Weibull distribution was also found with the noises of all the years

together, as the probability plot with 95% confidence bounds shows (Fig. 2). The result that the

Weibull distribution fits both the points of each year and the points of all the years together, on

the one hand, gives robustness to the assumption that the noise is produced by “extreme”

meteorological factors, and, on the other hand, makes this law reliable for performing tide level

forecast in both the short and the medium term.

Figure 1: Comparison between the observed tide

(black line) and the simulated tide (grey line)

relating to the year 2005; the simulated tide is

shifted to allow one clear observation; the window

shows a comparison between the two tides in a

time-interval of 300 hours.

4 References

Figure 2: Weibull Probability plot, with 95% confidence

bounds, relating to the positive noise of the

whole period 1999-2009.

Faggioni, O.; Arena, G.; Bencivenga, M.; Bianco, G.; Bozzano, R.; Canepa, G.; Lusiani, P.;

Nardone, G.; Piangiamore, G. L.; Soldani, M.; Surace, L. & Venzano, G. (2006). The

Newtonian approach in meteorological tide waves forecasting: preliminary observations

in the East Ligurian harbours, Annals Of Geophysics, Vol. 49, No 6, pp. 1177-1187

ISSN 1593-5213.

Kim SY, Terrill EJ, Cornuelle BD, Jones B, Washburn L, Moline MA , Paduan JD, Garfield N,7,

Largier JL, Crawford G , Kosro PM (2011). Mapping the U.S. West Coast surface

circulation: A multiyear analysis of high-frequency radar observations. Journal Of

Geophysical Research-Oceans Vol. 116 ISSN: 0148-0227.

Kotz, S. and S. Nadarajah (2001) Extreme Value Distributions: Theory and Applications, World

Scientific Publishing Company; ISBN 1860942245.

Manzano-Agugliaro, F., Corchete, V. & Lastra, X. B. (2011). Spectral analysis of tide waves in

the Strait of Gibraltar, Scientific Research And Essays, Vol. 6, No 2 pp. 453-462 ISSN

1992-2248.

Pawlowicz, R., Beardsley, B., Lentz, S. (2002). Classical tidal harmonic analysis including error

estimates in MATLAB using T_TIDE. Computer & Geosciences, Vol. 28, No 8, pp. 929-

937; ISSN 0098-3004.


Book of Abstracts - Poster Presentation 145

Estimation of wave energy potential of the Northern

Mediterranean Sea

Valentina Vannucchi 1 and Lorenzo Cappietti 2

1 Introduction

At present a large number of Wave Energy Converters (WECs) have been proposed. Extensive

review are available in the scientific literature such as the most recent Falnes 2007 and Falcao,

2010. WECs are usually categorized by: i) their distance from the shore; ii) type of interaction

with wave fronts; iii) type of take off system. The positioning of device can be: shoreline,

nearshore and offshore. The last two categories are characterised by a larger amount of

available wave-energy but at the same time the device construction, maintenance and energy

transport is more difficult. The WECs typologies are three: terminator is a device that physically

intercepts waves and has the principal axis parallel to the wave front; attenuator is a floating

device which works parallel to the wave direction and it has a lower area parallel to the waves in

comparison to a terminator; point absorber is a floating structure with small dimensions relative

to the incident wavelength and absorbs energy in all directions through its movements at/near

the water surface (Falnes, 2007). WECs convert wave energy in different way and some

significant examples are: submerged pressure differential, oscillating wave surge converter,

oscillating water column, overtopping device, wave roller (Falcao, 2010).

In order to assess the feasibility of the use of a WEC in a given site, a proper characterization of

the local wave climate and the available wave energy potentials have to be done. In this

perspective, the Mediterranean sea has received less attention since it is much less energetic

than the oceans. However the utilization of the available wave energy of the Mediterranean sea

could be of certain interest at least under some circumstance like WEC embodied into harbour

breakwaters. In this case of multifunctional structures, the cost of the infrastructures are shared

thus enhancing the value of use of the WEC.

2 Objectives

In this work an estimation of wave energy potential of the Mediterranean Sea has been carried

out.

3 Methodology

The analysis is based on wave data arising from: i) numerical models for wave generation

coupled with atmospheric models and ii) wave buoys facing the cost of Italy and France.

Numerical model wave data have been obtained by IFREMER that has developed a preoperational

system, called PREVIMER, aiming to provide short-term forecasts about the coastal

environment along the French coastlines bordering the English Channel, the Atlantic Ocean,

and the Mediterranean Sea.

The wave buoy data have been obtained by IFREMER, ISPRA, Carrara Port Autority and

Regione Toscana – Settore Servizio Idrologico Regionale.

The domain of the PREVIMER numerical models and the position of all wave buoys are

depicted in figure 1.

1

Università di Firenze-Dipartimento di Ingegneria Civile e Ambientale, Via S.Marta 3, 50139 Firenze, Italy,

valentina.vannucchi@dicea.unifi.it

2

Università di Firenze-Dipartimento di Ingegneria Civile e Ambientale, Via S.Marta 3, 50139 Firenze, Italy,

cappietti@dicea.unifi.it


146 5th International Short Conference on Applied Coastal Research - SCACR 2011

Figure 1: Location map of wave buoy

These wave data have been used in order to estimate the monthly mean and yearly mean wave

power per unit length of wave front, according to the formula (1) and the results will be

presented in the final paper in term of: i) contour maps (figure 2); ii) rose of wave power and iii)

scatter diagrams (Hm0,T).

2

1 g 2

P � �HmoT

(1)

m�1,0

64 �

with g acceleration of gravity [m/s 2 ]

π pi-greek constant [-]

ρ water density [kg/m 3 ]

Hmo wave height [m]

Tm-1,0 wave period [s]

Figure 2: Mean wave power in the period 2.07.09-31.03.11

4 References

Falnes J. (2007): Review - A review of wave-energy extraction. In: Marine Structures, Vol. 20,

pp. 185–201.

Falcao A. (2010): Wave energy utilization: a review of the technologies. In: Renewable and

Sustainable Energy Reviews, Vol. 14, pp. 899-918.


Book of Abstracts - Poster Presentation 147

Comparative analysis of wind generated waves on the Ilha

Solteira lake, by using numerical models OndisaCad and Swan

Adriana S. Vieira 1 , Conceição Juana Fortes 1 and Geraldo de Freitas Maciel 2

1 Introduction

The undergoing project ONDISA (Ondas no lago de Ilha Solteira), UNESP (1997, 2008), aims

to improve the understanding of hydrodynamics and morphodynamics inside a dam reservoir.

This will be achieved through the implementation of an interdisciplinary study that integrates

three distinct methodologies: field-data acquisition, laboratory investigation and numerical

modelling. One important aspect of this study is the evaluation of the effects of wind generated

waves on the lake margins and/or on the navigability security. The system under study is the

Ilha Solteira dam reservoir which is located at the São Paulo state, Brasil. The work presented

in this paper addresses the first and third aspects, i.e., the field-data acquisition and processing

and the numerical modelling of wind-generated waves. To characterize the system

hydrodynamics and its impact on the margins of the Ilha Solteira dam reservoir, it is necessary

to evaluate the local wave climate. This can be done using either in-situ measurements or

hindcast wind-wave models. So, several instruments were deployed in different locations to

characterize the waves and winds. These measurements, in spite of being very useful to

describe local wave characteristics, are of too short duration to characterize the long-term wave

climate. Besides, they also suffer from a restricted spatial representation of the wave conditions.

The use of numerical wind-wave models can overcame this aspect. Two examples of those

models are the nonlinear spectral numerical model SWAN, Booij et al. (1996), and the model

OndisaCad (Marques, M, (2007)).

This paper describes the in-situ measurements, the data analyses made, and the application of

the above numerical models to the study area. A comparison between in-situ measured data

and numerical results is made. These comparisons allow one to evaluate the performance of

the numerical models and its adequacy to characterise the wind generated waves at that region.

2 Study area

Figure 1 shows an overview of the Ilha Solteira lake, São Paulo – Brasil, with an extension of

100 km, at the northwest of São Paulo State.

Figure 1: Ilha Solteira: Overview and bathymetry.

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1 LNEC, Av. Do Brasil, 101,Lisboa – Portugal, (asvieria, jfortes) @lnec.pt

2 UNESP, Av. Brasil, 54, Ilha Solteira- S.P – Brasil, maciel@dec.feis.unesp.br

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148 5th International Short Conference on Applied Coastal Research - SCACR 2011

3 Methodology and Results

Several equipments for wind and waves measurements was used such as, for instance, an

directional wave buoy (ANSYS) and an anemometer (CAMPBELL) placed at different locations.

The available equipment consists of a remote station (model CR1000 datalogger), radio

modem, antenna unidirectional, solar panel and battery, housed in box a weatherproof.

For some wind and wave conditions selected from the data, SWAN and OndisaCad are used to

simulate the waves generated at inside the dam reservoir. Spectral model SWAN (Booij et al.,

1999), which takes into account the wave generation, propagation, attenuation and non linear

interactions between waves and currents phenomena, is a model that is usually employed in

open coastal regions although not so often in enclosed regions, such as estuaries or lakes. The

OndisaCad developed at the São Paulo State University (UNESP), calculates the wave heights

based upon the Sverdrup, Munk e Bretschneider, of Shore Protection Manual.

An example of the results obtained is presented in figure 2. This figure enables the identification

of the areas where the highest waves occur as well as the critical points for the navigation and

for the stability of the reservoir margins. Moreover, comparisons between numerical models and

in-situ data will be presented and discussed in the paper. This will permit to evaluate the

performance of each model and the adequacy of those models to preview wind generated

waves at this region. The main differences between numerical results are also discussed.

OndisaCad SWAN

Figure 2: Wave height field (generated by NE wind direction) – Ilha Solteira - S.P. - Brasil.

4 Acknowledgements

The authors acknowledge the support made possible by the projects financed by CAPES –

Conselho Nacional de Desenvolvimento Científico e Tecnológico contracts of refs. 0022101 and

PPGEE/FEIS-UNESP – Programa de Pós Graduação em Engenharia Elétrica- Faculdade de

Engenharia de Ilha Solteira-Brazil.

5 References

BOOIJ, N.R.; Holthuijsen, L.H.; Ris, R.C. (1996) – The SWAN wave model for shallow water,

ICCE´96, Orlando, pp. 668-676.

UNESP (1997, 2008) - Ondisa Project. Project support by FAPESP and FINEP brazilian

agencies.

Marques, M (2007) - Estimativa das máximas pistas de vento no reservatório da barragem de

Ilha Solteira, Estado de São Paulo - DOI: 10.4025/actascitechnol.v29i1.112; Acta

Scientiarum. Technology, Vol. 29, No 1 (2007).