To solve the problems that an erosion control dam provided in a valley mountain river is filled soon, blocks a mountain stream, forms a level difference and obstructs passage of water creatures, to control a sediment discharge of a river, and to eliminate sediment and accumulated mud in a dam or a lake.

A water replenishing tower having a slit-like water suction port in the vertical direction is erected on a dam inner wall upper side of a drain hole passing through a dam bank bottom part of an erosion control dam, a lower end is brought close to the drain hole and opened, and blockage of a drain hole inflow port is prevented. On an upstream side erosion control dam inner bottom surface of the water replenishing tower, a covered water channel in the shape of turning down a groove-like body, for which a slit-like mud suction port is opened along a lower installation surface, is extended and disposed toward the upstream, and a sediment amount inside the erosion control dam is reduced. To the downstream end of the drain hole, a fish way to a lower riverbed is connected. Further, in the erosion control dam in the case of controlling the sediment discharge of the downstream river, a valve is provided on the drain hole and is opened and closed to control discharge and storage of the sediment inside the erosion control dam.