In the Agano River estuary flowing into Japan Sea, bars at the mouth are developed from both river banks. The bar causes the river discharge capacity to decrease and the water level to rise. Therefore, it is important to understand mechanism of river mouth bar flushing during a flood event. One of the authors has shown that flow and bed variation during a flood event may be explained by means of a suitable numerical analysis method using temporal changes in observed water surface profiles effected by various events in the river. The objective of this paper is to clarify flushing at river mouth bar during a large flood by temporal observed water surface profiles and the numerical analysis.
