Wave dissipation by vegetation for coastal defense in the Western Mekong Delta under climate change

Abstract

Abstract The combination of the Mekong Delta dyke-mangrove system effectively protects the hinterland against flooding and erosion in extreme conditions for decades since they could dissipate waves and currents efficiently. However, literature and satellite data indicate that severe erosion happens along the Western sea-dykes of the Ca Mau coast caused by increased intensity of storms due to climate change. State-of-the-art wave transformation models are used to predict the influences of wave propagation and wave overtopping discharge over sea dykes and/or associated with mangrove ecosystems under extreme typhoons, which cooperates with both high – frequencies (HF) and low – frequencies (LF) waves. Results confirm that the HF wave quickly dissipates in shallow water, whereas the LF wave is dominant and penetrates over a longer distance. At dyke toe, the wave height through vegetation is substantially diminished, approximately ten times less than that in the sea-dyke solely. However, the modelling wave overtopping discharge seems to be overestimated compared with the standard-based formula.