Numerical simulation of detached breakwaters for mangrove restoration in Bengkalis Island, Indonesia

Abstract

This paper presents the application of detached breakwater to reduce wave energy for protecting mangrove planting site. Initial planting of mangroves still needs seawater for their growth, but they will be distracted by the big wave. How is the detached breakwater should be designed for this purpose is the objective of this research. This research simulated the wave propagation at the existing condition and under some alternative designs of detached breakwater to find out the optimum design of detached breakwater for mangrove planting site. The CADMAS-SURF is a numerical model that was used for the simulation. Bengkalis coast in Indonesia was picked up as study area of this research. The mangrove degradation and the severe coastal abrasion have occurred in this area for long period. The simulation result shows that in the high tide condition, the wave height and wave velocity at the mangrove plantation area are about 1.12 m and 3.86 m/s respectively in the case of the existing condition. In this case, the initial mangrove plantation cannot be applied because it will be destroyed by the wave. By applying breakwater both for rubble mound type and vertical wall type, the wave height and the wave velocity were reduced to 0.69 m, 2.39 m/s and 0.72 m, 2.31 m/s respectively. In this case, the initial mangrove plantation can be applied because it will not be destroyed by the wave.