The Beneficial Effects of Mangrove Forest to Sea Defence

Abstract

At many locations, especially in deltaic areas, dikes and other flood defence structures are needed to protect the hinterland against flooding by surges (typhoons, hurricanes) and/or tsunamis. Dikes are quite costly, and mangroves in front of the dike will lower the costs of the dike. Mangroves in general allow dikes to be lower and narrower. In this chapter the hydrodynamic effects of mangroves on dikes are elaborated as well as the financial impact on the costs of dikes. The main advantage of a mangrove forest in front of a dike is that the forest decreases the wave height just in front of the dike, and therefore the freeboard needed to cope with these waves can be considerably less. Because the waves in front of the dike are small due to the mangrove forest, often no costly revetment structure is needed any more. In this chapter computational methods are presented to determine the direct benefit for dike construction.