RESEARCH ON THE COMPREHENSIVE METHOD FOR ANALYZING THE DAMAGE MITIGATION EFFECTS OF FLOOD CONTROL FACILITIES FOR FLOODS EXCEEDING THE DESIGN LEVEL

This research aims to develop a method for analyzing the operation of flood control facilities towards minimizing damage from floods that exceed the design flood. Specifically, we propose a method in which the operations of complete sets of flood control facilities, such as flood control basins, pumping stations and sluiceways, are taken into account in comprehensive flood analysis for inland water and bank overflow. We studied the Chitose River, which is a tributary of the Ishikari River. The Chitose River is affected by backwater from the Ishikari River on a roughly 30km reach. Because most of the Chitose River basin is flat, low lying land, the flooding risk is high. Using our method, we performed flood analyses that incorporate the operations of flood control facilities being developed in the basin. The analyses reproduced the following: 1) record flooding of 1981 and 2) assumed flooding that exceeds the design water level. The study indicates that our proposed method is able to comprehensively analyze flood control facilities and is useful for examining countermeasures against floods exceeding the design water level, which are expected to increase due to ongoing climate change.