2005 Volume 18 Issue 1 Pages 35-43
Record-breaking rainstorms by Typhoon 10 attacked a wide area of Hidaka districts in Hokkaido from August 9 to 10 in 2003. All of river basins distributed in the districts suffered from disastrous economic damages including the eleven toll of dead and missing. The flood flow resulting from heavy rainfalls caused by Typhoon 10 surpassed the 100-year design flood magnitude in the Saru River, which is designated as Rank A river.
The water levels at some points along the Saru River were at the margin of the top of embankments. The peak inflow to Nibutani Dam, which is managed by the Regional Hokkaido Development Bureau, was more than the design flood discharge by 1,000m3⁄s.
The present paper examines in detail the dam operations for flood control at Nibutani Dam, based upon valuable data of forecasted inflows as well as released outflows. It follows from the results of analysis that the gate operations carried out in abnormal situations of the August-Flood played a significant role in reducing the water levels by about one meter at Biratori gauging station and minimizing the flood damages downstream of Nibutani Dam.
