UNDERGROUND WATER TABLE AND BEACH FACE EROSION

Abstract

Numerical results show that the beach face of a tidal beach could be considered erosive due to the action of the surface flow formed by the escape of groundwater unless the action of moderate accretive waves, and that the effect will be intensified when the mean level of water table is higher than the mean sea level. Experimental results show that waves act to conceal the effect on the whole. These results suggest that the action of accretive waves are indispensable to maintain a tidal beach in a equiliblium condition. They also suggest that the cause of erosions of Surigahama beach and Jso beach was accumulative workings of the surface flow and insufficient wave action for the restoration during high tides.