PREDICTION OF BEACH CHANGES AROUND NUMAKAWA-DAINI FLOODWAY ASSOCIATED WITH IMPROVEMENT OF FLOODWAY

Abstract

 At Numakawa-daini floodway located on the Fuji coast, a plan converting the ordinary-type floodway into a setback-type floodway was made, by which the mouth of the floodway is moved from offshore of the shoreline to landward of the berm. To realize the plan, the influence of the conversion of the type of the floodway to the nearby coasts should be predicted beforehand. In this study, a numerical simulation using the contour-line-change model was carried out to predict beach changes when the floodway type is converted from ordinary-type to setback-type. As a result, it was predicted that the shoreline retreated in an area of approximately 1.5 km upcoast of the floodway, and the maximum shoreline recession was 15 m in 10 years.