Numerical simulation of debris flows occurred in Marumori in 2019 and countermeasures against debris flow using the numerical simulation result

On October 12-13, 2019, torrential rains caused by Typhoon Hagibis triggered multiple debris flows in Koyasu, Marumori, Miyagi Prefecture, Japan. The debris flows destroyed houses and four people died. In this study, the flow characteristics of the debris flows were clarified by field surveys and two-dimensional numerical simulations, and future countermeasures against debris flows were discussed. The calculation results show that a house 40 meters north along the road had its first floor damaged, but the second floor was undamaged. This house was the former home of the victims. If they had evacuated to the second floor of this house, they might have been able to survive. In other words, if the flow characteristics of the debris flows are clarified in advance by numerical simulation and the safe area is recognized, it is possible to increase the probability of survival by securing a temporary shelter in such a location and the human casualties can be greatly reduced.