Wave Attenuation by Wetland Vegetations

Wave attenuation by wetland vegetation is a concept that uses plants and vegetation
instead of hard structures such as breakwaters, revetments or seawalls to dissipate the
wave energy. The usage of hard structures has been proven to be obstructive and
hazardous to the local enviromnent either during the construction or even after the
completion of the structures. Another alternative which is more eco friendly and less
obstructive is by using vegetation as wave attenuators. The objective of this study is to
determine the level of effectiveness of the vegetations in attenuating waves. Another
objective of the study is to find a suitable species that will survive in the climate
conditions in Malaysia and will have the similar effect on wave attenuation as other
species that have been tested before. For the first semester, the concept was studied by
using previous researches on the effects of other plants located in countries which have
different weather conditions and climate compared to Malaysia. The study was continued
the following semester where experiments have been carried out using a wave flume and
the determination of the attenuation effect by the mangrove model is based on the
Transmission coefficient, C, The values that were evaluated were the Incident Wave
Height, Hi, actual wave height, H and wave period, T. The variable parameters used in
the experiment to determine the transmission coefficient, C1, were wave period, water
depth and the number of mangrove beds. The experiment was done by using mangrove
beds, comprising of 100 bamboo sticks with a diameter of 2mm placed in a 300 mm x
200 mm concrete bed placed in the wave flume. The initial wave height and actual wave
height was compared .. The initial testing shows that the mangrove model is capable of
attenuating up to 40 % of the wave height in various depths thus showing that the concept
is practical in wave attenuation. Shallow water depth, low wave period and higher
number of the mangrove model beds show a higher reduction in transmission coefficient.
Throughout the experiments done and after analyzing the results, it can be concluded that
wetland vegetation has the capability of attenuating wave energy even though it is not as
effective as hard structures