2006 年 50 巻 p. 325-330
Urban developments cause serious changes to watersheds conditions by decreasing storage area, introducing pavement and channeling. As a result, the peak discharge has been increasing and the arrival time of peak flow becomes early. The purpose of this study is to investigate the empty capacity of irrigation ponds in the Mikasa River watershed and to clarify flood control capacity of them. The result of this study, the catchments area of all irrigation ponds was about 18%, the capacity of flood control was about 450, 000m3 in the Mikasa river watershed. To estimate the flood control ability of irrigation ponds, we applied the distributed runoff model considering ponds effects about flood disaster in July 19, 2003. The result of calculation showed that the peak discharge at the Sanno Bridge decreased 36m3/s by the irrigation ponds.