Influence of Groundwater Table on Beach Profile Dynamics

Civil Engineer, Department of Civil Engineering AM (IESL), BSc Eng. (Hons) (Peradeniya), M.Eng. (NUS) Senior Lecturer in Engineering, Department of Civil Engineering M. (IES), M.(IEEE), M. (AGU), BEng. (Hons) (NUS), M.Eng (NUS), ScD. (MIT) A systematic study of the influence of coastal groundwater table on beach profile changes have been conducted experimentally. The purposes of this study were to investigate experimentally the influence of elevated groundwater table on beach profile changes and to investigate the function, performance and optimum method to install a coastal drainage system. The beach responses to different elevated groundwater tables and porous layers were examined and compared with a normal beach. It was found, from the study, that the elevation of the groundwater table has a major influence on the beach profile changes. Beach erosion, by erosive waves, was enhanced and beach accretion by accretion waves was reduced or erosion types convert to accretion types. The mechanism and quantitative variation of sediment transport was directly related to the elevation of groundwater table relative to mean sea level. The beach erosion by erosive wave can be reduced or erosive wave can convert to accretion wave by installing drainage layers inside the beach. It also can increase the effect of a recovery wave on the beach. The effectiveness of the system depends on the speed of the infiltration of water through sand to the porous layer (location of porous layer relative to beach face), depth of scouring and gradient of percolation towards onshore