2021 Volume 77 Issue 2 Pages I_97-I_102
In recent years, large-scale floods such as heavy rains in July 2018 have occurred frequently. On the other hand, due to the delay in river improvement works, there are many dams where provisional operations are being carried out by devaluing the flood control start flow rate, and there are some cases leading to the emergency spillway operation during extreme floods. The purpose of this study is to propose a method to determine the dam flood control operation method that can reduce the damage not only in the frequent small and medium-sized floods but also in the large-scale floods. In this paper, the flood control operation method of Hiyoshi Dam, which is located in the upstream of Katsura River, was studied. Firstly, return periods of large ensemble rainfall events (d4PDF) were evaluated and then we conducted rainfall runoff inundation analysis to know how the dam discharge, flooded area, economic damage in the downstream area, etc. change depending on the flood control operation method. As a result, we proposed a method to quantitatively compare the effects of dam flood control operation methods, including those without dams, and to select the most effective dam flood control operation method under various scales of rainfall groups.
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