LONG-TERM BEACH CHANGES ON SHICHIRI-GA-HAMA BEACH AND SHORELINE ADVANCE DUE TO BEACH NOURISHMENT

Abstract

 The causes of beach erosion on Shichiri-ga-hama Beach were investigated by the comparison of aerial photographs and the analysis of shoreline change. Narrow Multi-Beam survey was carried out to investigate offshore seabed topography in detail. As a result, the main factor of beach erosion was assumed to be due to the imbalance between eastward longshore sand transport turning around Point Inamuragasaki and the sand supply from the Yukiai River. The beach material excavated from the backshore was temporally placed near the shoreline during the construction period of Route 134 on this beach, and this substantially effected as beach nourishment, implying the effectiveness of beach nourishment.