2008 年 52 巻 p. 361-366
Urban development causes serious changes to watershed conditions by decreasing storage area, introducing pavement and channeling. As a result, the peak discharge has been increasing and the arrival time of peak becomes early. The purpose of this study is to investigate the state of retention facilities such as irrigation ponds and paddy area in Mikasa River watershed. The result of investigation shows the rate of the capacity of flood control of dam, ponds and paddy area are 37.1%, 14.6%, 48.3% and total capacity is 3, 063, 000m3.
For the estimate of the storage facility effects, we applied the distributed runoff model considering ponds and paddy area effects. The result of calculation showed that the peak discharge at Sanno Bridge decreased 36m3/s by dam, 31m3/s by ponds and 36m3/s by paddy area.