A case study on influence of construction of detached breakwater and harbor breakwater to river mouth bar

The changes in river mouth bar topography triggered by the construction of detached breakawaters and habor breakwaters in the ajacent area of the river mouth were analyzed through the case study. Three rivers, the Torikai, Toshi and Iwato rivers, on Awaji Island in Hyogo Prefecture were selected as the study area. It is concluded that retreat of river mouth bar may be caused by the disrupion of continuous longshore sand transport due to structures and creation of wave calm zone in the area next to a river mouth by construction of breakwaters, which facilitates longshore sand movement. Key words: river mouth bar, beach changes, detached breakwater, aerial photo