suds modelling for surface water management - SUDSnet

SUDS MODELLING FOR SURFACE
WATER MANAGEMENT
J Bryan Ellis 1 , Christophe Viavattene 2 and Jennifer Laight 3
1
Urban Pollution Research Centre, 2 Flood Hazard Research
Centre, Middlesex University, London. UK
3
Ove Arup & Partners, Solihull, UK
SUDSNET International Conference 2012. Multiple
Benefits from Surface Water Management.
Coventry . 4 –6 September 2012

33% of urban flooding
during extreme storm
events due to pluvial
overland surface flows
Local Authorities now
responsible for surface water
management and SWMPs
Future climate
change and new
developments will
exacerbate the
pluvial flooding
problem

TOOLS TO IDENTIFY
CRITICAL DRAINAGE AREAS
AND MANAGE THE FLOOD
RISK
• where flooding will occur;
distribution and flow paths,
depths. velocities etc
• opportunities for mitigating
SuDS measures
• improved public/stakeholder
engagement
• assist forward emergency
planning

Identifying Critical Drainage Areas:
• identify “hotspot “ flooding during extreme
storm events
• quantify depth and spatial distribution of
flooding
• identify flood flow paths
• Identify appropriate temporary storage,
attenuation and treatment facilities

1D/2D COUPLED MODELLING FOR
SURFACE PLUVIAL FLOODING
Flow Path
2D Surface
Flow
Manhole
Manhole
1D
Sewer
Flow
SEWER
Identifies and quantifies flood depths
and flow paths during extreme storm
events

Exceedance
Overland flow
Surface
surcharge
Surface water sewer
EXIT
OVERFLOW
S
Surface
depression
“pond”
Exit point from
0.5m raster cell
cascade
Surface flooding depths and
flowpath delineation
algorithm follows the lowest
exit point from each DTM
cell i.e rolling ball technique

Shelton
HEN LANE
CATCHMENT
COVENTRY
90ha; 30%
Impervious
Bridge
Hen

PREDICTED FLOW DISTRIBUTION AND EXCEEDANCE
OVERFLOWS FOR AN EXTREME EVENT
Based on 1D Hydraulic
Modelling e.g STORM,
InfoWorks CS etc

2D DATA INPUT TO CREATE DIGITAL
TERRAIN/ELEVATION MODEL (DTM/DEM)
Need topographic background for developing the 2D
surface area with high vertical and spatial resolution
e.g ± 2/3cm vertical and 0.5m raster cell
• detailed large‐scale micro‐topographic map (with
reinforcing “groundtruth” survey)
• aerial/satellite images (including Google Earth and
Street Views)
• LiDAR survey (aerial or ground mobile)
Need for the selected topographic survey to be georeferenced

Micro-topographic DEM
HEN LANE CATCHMENT.
COVENTRY Raster Cell 0.5m

ARUP mobile terrestrial LiDAR
EA unfiltered aerial LiDAR
EA filtered aerial LiDAR

COventryResults

MU2
WHAT SUDS DRAINAGE
CONTROLS AND WHERE TO
LOCATE THEM????
SUDSLOC model

Slide 17
MU2
To be changed with new results
Middlesex University, 12/05/2011

GIS INTERFACE
SUDSLOC
USER‐FRIENDLY INTERFACE
•Is a Geographic Information Decision System Support tool
•Provides support for the identification and location of appropriate SUDS
at urban scale
•Supports the integration of data (quantitative and qualitative) from a
variety of sources to enable the investigation of the potential benefits of
SUDS
•Is designed to communicate with storm runoff modelling approach

GIS sewer network GIS Landuse SUDS MCA Matrix
SUDS
‐ Storm event rainfall profiles
‐ Landuse type and runoff coefficients
Decision
‐ Surface and soil type/character
Support
‐ Groundwater profiles
‐ 2D DEM micro‐topography SUDSLOC
• 2D Surface flood maps
• Flood damage costs
• SUDS types and location
• SUDS volume reduction
• SUDS pollutant performance
GIS DECISION
SUPPORT
FRAMEWORK
MANAGER
‐ SUDS characteristics
‐ Site criteria
‐ MCA Indicators and
Benchmarking
‐ Pollutant removal
potentials (UoP)
SUDS
Catalogue ,
Costings and
Photographs
External Inputs e.g
STORM
InfoWorksCS
FloodArea 2D
EcoSWM
Depth‐damage
curves

SUDS Assessment Components
• Site Criteria
Land use, soil type, slope, depth to groundwater, drainage area, presence
of ‘flat roofs’
Scale unit : road, car park, building, pavement etc
• SUDS pollutant removal potential (Ranking)
Pollutant (TSS, BOD, COD, Nitrates, Phosphates, Cd , Cu,...)
Unit Operating Processes (UoP); Removal Process considered (adsorption,
settling, microbial degradation, filtration, plant uptake, volatilisation and
photolysis)
• Multi‐Criteria Comparator (Ranking)
Technical, environmental, economic, operation and maintenance, social
and legal criteria
• Catalogue of information
SUDS types/photographs, design specifications, operational
requirements, costings, case examples and reference listings

Interactive Map functionalities
Potential Areas
Site‐by‐site assessment
Add a SUDS and export
Flow destination

SUDSLOC: INSERTION OF
INFILTRATION BASINS
(Hen Lane, Coventry)

Roundabout Sewer Node
FLOW
OVERFLOW

COMPARISON BETWEEN PREDICTED FLOW
DISTRIBUTIONS WITH AND WITHOUT SUDS INSTALLED
A total decrease from 1726 m 3 to 1226 m 3 (30%)

CONCLUSIONS
• GIS‐based 1D‐2D coupled modelling provides appropriate
methodological approach for identifying surface water flood risk
• requires appropriate LiDAR micro‐topographic input at detailed
spatial and vertical resolution; 0.5m grid cell and ±2 ‐ 3cm vertical
resolution needed for satisfactory definition of flood flow paths,
depths and velocities
• coupled SUDSLOC model selects and locates appropriate mitigating
SUDS control devices and quantifies flow benefits
• coupled modelling methodology offers flexible tool for mapping
urban pluvial flooding, choosing mitigating control options together
with flexible public communication capability and capability for
emergency planning