2016年北海道豪雨災害における空知川幾寅地区の破堤・氾濫要因の検討

抄録

There was a record-breaking rainfall in eastern Hokkaido during the end of August 2016. This rain and associated flood caused the levee breaches at two places and inundation disaster in Sorachi River in Ikutora region, Minami Furano town, Hokkaido. The field surveys and the aerial photographs taken after the flood showed that the inundation disaster was caused by the levee breach at the upstream reach of Ikutora, and this flood flow returned to the Sorachi river main channel from the floodplain, resulting in another levee breach at the downstream reach. Subsequently, we performed numerical simulations of the flood event and associated river bed evolution and levee breaches to investigate detail processes of this flood disaster. The results indicated that the upstream levee breach was caused by both bank erosion and overtopping flow and the downstream levee breach was caused by the overtopping flow.