THE REPRODUCTION SIMULATION OF THE INUNDATION AND RUNOFF IN THE NAKAGAWA SYSTEM BY TYPHOON HAGIBIS

抄録

 Typhoon Hagibis caused the serious flood damage on the Naka River, which is one of the major class A rivers in the Kanto region since the flood damage in 1986. In this study, we recorded the disaster situation and conducted field survey in the damage concentrated segment of the bank breakage and overflow. In addition, we conducted the runoff analysis for the Naka River Basin and the flood analysis for some regions near the Nakagawa River. As a result, it is clarified that 1) the large-scale inundation (average inundation depth: 1.9m) occurred near the Fujii and Tano rivers that are tributaries of the Naka River and 2) the inundation continued for a while (four days) because the drainage capacity was not sufficient. In addition, based on the water level changes of the Naka and Fujii rivers and the traces of the flood flow, it was inferred that the Fujii River was affected by the backwater. Furthermore, the reproduction simulation, which combined the runoff analysis and the flood analysis, reproduced 1) the inundation depth obtained by the field survey and 2) the backwater in the Fuji River.