COASTAL MANGROVE SQUEEZE IN THE MEKONG DELTA

The root, stem and canopy structure of mangrove forests create an extremely efficient system in attenuating waves and currents. Mangroves are therefore known as a natural system for coastline protection against flooding and erosion. However, mangroves degradation and associated coastline erosion are frequently observed along the Mekong Delta coast, one of the largest mangroves area in the word. The southeastern and eastern Mekong Delta coast are now hosting many sea dikes constructed to extend agri- and aqua-cultivation areas. Although the intention has been to improve the conditions of the Mekong Delta population to improve their life, it causes mangrove squeeze along the coastline. The basic assumption behind our work is that there is a critical minimum width of a coastal mangrove forest strip to keep its ability to stay stable or, once surpassing the minimum width, to promote sedimentation. Our research based on both literature and satellite data shows that an average width of 140 meters of mangrove forest is necessary for a healthy mangrove forest state along the southeastern and the eastern Mekong Delta coast. We are using a state of the art wave propagation model that includes both short and long waves to analyze wave attenuation as a function of mangroves width. Our results show that short waves are attenuated very quickly even before they can reach the critical width of the mangrove forest. Infragravity waves however penetrate over much larger distance. We therefore hypothesize that long wave attenuation will be the major factor of influence to the health of a mangrove forest.