2022 Volume 78 Issue 2 Pages I_205-I_210
Beach erosion of the Seisho coast was investigated on the basis of shoreline analysis using aerial photographs. The hotspots of erosion of the coast were located on the Kozu and Maekawa coasts east of the Morito River mouth, and the area between Ninomiya IC of the Seisho Bypass and the Kuzu River mouth. The cause of the erosion on the Kozu and Maekawa coasts was due to the offshore discharge of sand via a submarine canyon offshore of the Morito River. In the latter case, sand has been transported away by eastward longshore sand transport. The entire volume of eroded sand was estimated to be 2.86×106 m3 between 1973 and 2020. Assuming that the entire volume of sand was transported into the submarine canyon, the rate of discharge was estimated to be 6.1×104 m3/yr.
