FIELD SURVEY NEAR DETACHED BREAKWATERS AND NUMERICAL SIMULATION OF MORPHOLOGICAL CHANGES USING XBEACH MODEL

Abstract

 In the present study, the field survey and numerical simulations of morphological changes near the detached breakwaters were carried out at the Aoyama beach, Niigata, Japan. The field survey was conducted in September and November, 2020. In these surveys, UAV photogrammetry was applied to obtain Digital Elevation Model (DEM). Furthermore, bathymetry measurement using sonar was carried out in September. As a result, although a slight sedimentation was measured behind detached breakwaters, an overall erosion was observed over sea level in Aoyama beach. In addition, in the results of the numerical modellings, the topographic changes of non-hydrostatic mode are in better agreement with the field survey results than that of surf beat mode. In detail, an overall erosion tendency and a slight sedimentation tendency beneath sea level were calculated in non-hydrostatic mode, which is qualitatively and specially consistent with the observations. From these results, it can be indicated that beach profile changes at Aoyama beach were mainly caused by high waves occurred in this period.