Field Surveys and Numerical Simulations of Beach Scarp in Niigata Coast, Japan

In this study, we investigated morphological changes including the formation of beach scarp behind the breakwaters based on field surveys and numerical simulations at Aoyama beach in Niigata coasts, Japan. The morphological changes on the land area were analyzed by using digital elevation models (DEMs) constructed by UAV photogrammetry. The changes beneath sea level were analyzed by echo sounders. As a result, the land area showed a trend of erosion with beach scarp, and the beneath the sea water a salient was formed toward the breakwaters, which was consistent with the result of numerical simulation by using XBeach. The numerical analysis implied that the formation mechanism of beach scarp was a result of avalanching on steep slope mainly because of erosion effect amplified by water level rise behind the breakwaters. It can be identified that the formation of beach scarp was caused by high wave event and initial steep slope.