CLIMATE CHANGE IMPACT ON RIVER FLOODING AT UPSTREAM REGION OF THE ARA RIVER DUE TO TYPHOON HAGIBIS IN 2019

River flood disaster may increase due to climate change. To evaluate the impact of climate change on river floods, in this study, pseudo-warming ensemble experiments under +2 and + 4 degree scenarios were conducted using numerical simulation for not only rainfall and runoff, but also river flow and flooding, in which there have been few previous studies. Study target was the flood in the upstream reach of the Arakawa River due to typhoon Hagibis in 2019. Comparison of ensemble average of the +2 (+4) degree scenario and the current case showed that total rainfall, peak discharge and water level increased by 7.1 (33.8)%, 12.2 (35.8)%, and 130 (286)%, respectively. In the current case, no inundation occurred, but the inundation occurred in 6 or 18 of 20 members of the +2 and + 4 degree scenarios, respectively. These facts suggested that floods that exceeded H.W.L. but did not cause flooding would increase the possibility of flooding due to the progress of climate change.