INVESTIGATION ON EFFECTIVENESS OF MANGROVE FOREST IN COASTAL PROTECTION

Mangroves itself is a unique ecosystem which requires special attention and management. Its location which is between the land and the sea pays an important role in fisheries, coastal protection and conservation of biodiversity of both flora and fauna. Mangroves known as an important ecological function in mitigating coastal erosion by reducing the energy of waves, tidal currents and storms that caused coastline erosion. Mangrove trees have the root systems that help to keep the soil together and protect the coastal zones against erosion and extreme weather. Studies concerning the characteristics of mangrove vegetations and wave that influence the ability of mangrove forests in dissipating surface wave is presented in this paper. The field assessments were conducted to measure the geometrical features of the mangroves, the wave attenuation, and wind induced surface wave energy in mangrove forest, specifically Rhizophora spp. This study aimed to quantify the wave height reduction of 5 years old mangroves forest with various mangrove densities, water depths and incident wave heights. The dimensions of the mangroves at site were measured to fabricate the mangrove model for subsequent laboratory investigation in the wave flume. The experimental showed that the wave height reduction in the area of 100 m mangroves of age 5 years old was 2 times larger than area without mangroves due to waves could not propagate freely through the gaps between mangrove plants.. Then, the difference of wave reduction between tandem and staggered arrangements was approximately 2% which is not significant. Result of wave reduction with respect to age group on different forest densities have showed that the mangroves of age 10 years old gave larger of wave reduction compare to 5 years old due to larger friction by the trunks and root system. Through laboratory testing, it is shown that the size of trees may affect the incoming wave heights. At the shallow water depths, the higher the wave heights, the more wave reductions occurred due to more wave energy was dissipated. Even though the root system of a five years old mangrove is not a completely developed aerial root systems, the laboratory experiment revealed that the root structure is still able to provide substantial wave dissipation