Flood Capacity of Shirakawa River at Tatsudajinnnai Area in Kumamoto Prefecture

In the Shirakawa River, remarkable deformation due to sediment deposition was observed after the river channel improvement work. The sediment deposition was observed at the bend of the river channel. In this research, a model experiment, a quasi-three-dimensional numerical simulation and planer two-dimensional bed variation analysis were conducted in order to evaluate the effect of river bend curvature variation caused by improvement works on channel response and flow capacity. In the model experiment, large sandbars were formed, and the channel become narrower. In the numerical simulation, flood flew over sandbars and gravel deposited on sandbars, which caused decreasing of flow capacity. The gravel deposition was most active when the flow charge was in its peak. There was less inundation at the areas where sediment deposition was occurred.