There are a lot of river with long gorge sections in Japan. Because considering the balance of upstream and downstream reaches is the base of the flood control management, river improvement in gorge sections is a fundamental issue. So, it is important to understand the flood propagation mechanism in gorge sections. But because of the lack of the observed data in gorge sections, enough studies have not been conducted.

In this study, we show the mechanism of flood propagation and the effect of the channel form on flood propagation in the gorge section of the Go River and Kitakami River from observed data and using the unsteady 2-D flow analysis.