DEPOSITION IN MAIN CHANNELS AND SCOURING ON FLOODPLAINS CAUSED BY SAND BARS DURING FLOODS

Abstract

Large-scale scouring was generated by the 1998 flood of the Shokotsu River resulting in revetment damage. The main channel was filled up by deposition during the 1981 flood of the Toyohira River. The cause of this scouring of the floodplain and deposition in main channel was considered for the purpose of understanding the impact of flood to channels. It seemed that the scouring and deposition was caused by the formation of double-row bars. In general, the nondimensional shear stress at the floodplain is smaller than at the main channel. Therefore, it seems that the floodplain is hard to be scoured. However, when the elevations of floodplain surface and main channel bed are not so different, a lot of deposition and scouring in channel is caused by multi-row bars during large scale flood. This phenomenon is shown in this paper using actual river data.