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1 INTRODUCTION
Malaysia Water Research Journal
The main function of mostly available coastal protection structure is
solely to protect shoreline from erosion. Some structures such as groin and
offshore breakwater are more effective as those systems encourage sediment
accumulation at leeside. However the installation of such systems are very costly
and interfering with natural beach hydrodynamic processes. Wave breaking
zone and the direction of longshore drift are directly affected hence creating
adverse effects such as erosion to the other side of installation. Interference
in this dynamic equilibrium leads to a change in sediment supply causing an
increase or decrease in local sediment budget, resulted to accretion or erosion,
respectively (Ghazali, 2006). In addition, the reflected wave energy back to
offshore may cause beach profile changes due to resonant effects (US Army
Engineers, 1984).
Seawall type of coastal protection can be considered as shoreline defense
applications. Seawall is defined as an armoured revetment and an embankment
with or without structural crest elements (Allsop, 1986). The protection wall is
usually built parallel to the shoreline in order to prevent soil from sliding while
offering protection from wave impact (Kamphuis, 2000). The construction
material includes of concrete, rocks, steel, timber, rubber tyres, and sandbags
(Pilkey, O. H.; Dixon, K. L., 1996). The shapes of coastal structures are determined
by the use of the structure and generally can be categorised as vertical or
nearly vertical, sloping, convex-curved, concave-curve, reentrant, or stepped.
Shoreline defense structures, such as seawall and coastal blocks are situated
beyond active hydrodynamic zone hence minimising adverse implication
towards natural processes.
The aim of this study is to develop an innovative coastal block protection
structure with minimum impact to existing coastal hydrodynamic processes.
NEXC Block is designed and placed within Mean Higher High Water (MHHW) and
Highest Astronomical Tide (HAT) water level to minimize the impact, and installed
with sufficient toe protection for stability and efficiency. It protects the beach
and acts as a wave breaker during monsoon season, while the system also
encourage natural sediment accumulation on calmer period. NEXC Block, or
NAHRIM Coastal Erosion Protection and Beach Expansion Block was developed
by National Hydraulic Research Institute of Malaysia in 2015 – 2016. This applied
research approach include conducting research and development using
numerical models, experimental testing and pilot projects at selected sites.
Main objectives of 2D wave flume study include:
a) To determine the ability of NEXC Block as a protection structure against
coastal erosion,
b) To assess the efficiency of NEXC Block as a coastal expansion mechanism
in laboratory scale,
c) To evaluate and verify the interaction between structures – water level –
wave – sediment processes with NEXC Block site installations.
Institut Penyelidikan Hidraulik Kebangsaan Malaysia (NAHRIM)
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National Hydraulic Institute of Malaysia (NAHRIM)