抄録
There are many points the dams of whose which are a river transected structure thing are unknown about the influence which it has on the physical environment of a river downstream site, specifically river channel form, stream bed material, drifting sand, and a flow. Furthermore, about the stream bed change accompanying dam withdrawal, there is no empirical research in Japan. In this research, it investigated in the Arase Dam downstream site where withdrawal is started from September, 2012. As a result, the sandbar area in the Arase Dam direct lower stream of the correlation with the dam annual maximum outflow rate was weak, and the influence from the amount of removal of the earth and sand deposited on the dam lake became clear.
