BATHYMETRY CHANGES AROUND LARGE-SCALE SUBMERGED BREAKWATER ON THE NIIGATA COAST

Bathymetry data obtained for 16 years around a large-scale submerged breakwater on the Niigata coast were analyzed. A local scour has developed shoreward of the submerged breakwater and expanded according to the extension of the breakwater. The maximum scour depth reached about 4 m. However, in the area protected by the submerged breakwater and groins, the influence of the scour is confined just shoreward of the breakwater, and the scour does not have a strong influence on the beach stability near the shoreline. Furthermore, in contrast to detached breakwaters, the submerged breakwater did not show erosion but a small level of accretion seaward of the structure.