ANALYSIS OF TOPOGRAPHIC CHANGES IN 2014-2016 PERIOD ON SEISHO COAST

Abstract

 Narrow Multi-Beam survey data collected in the area offshore of the Seisho coast in 2014 and 2016 were analyzed. The analysis was carried out, focusing the typical accumulation and erosion pattern which is caused when longshore sand transport was blocked by the offshore reef or groins, and the characteristics that the change in seabed topography decreases seaward and ceases near the depth of closure, instead of simple comparison of the obtained NMB data. Six areas, such as the Sakawa River mouth, Odawara Parking area, the Ninomiya coast where beach nourishment using coarse sediment, and others, were selected, and longshore sand transport and the depth of closure at several locations were evaluated. As a result, it was found that westward longshore sand transport dominated during the observation period, and longshore sand transport was evaluated to be 2.5×10⁴ m³/yr at the Kuzu River mouth.