EVACUATION RISK ASSESSMENT ON FLOODING SLOPING ROAD DURING TYPHOON HAGIBIS AND PAST DISASTERS IN KAMAISHI

Abstract

With increasingly heavy precipitation due to climate change, it is crucial to quantitatively assess flood risk. During Typhoon Hagibis, which lasted from the 12^th to the 13^th of October 2019, flooding obstructed evacuation routes. Studies have been conducted to evaluate the evacuation risk of flooded roads. However, a comprehensive risk assessment of flooded sloping roads has not been reported. This study aims to establish a method to estimate the risk of evacuation on flooded, water-flowing slopes. The predicted hazard and inundated areas from past disasters are shown in the hazard map of Kamaishi City. This study presents a risk evaluation of pedestrian evacuation on slopes utilizing the fluid force calculated using the estimated velocity and water depth for the maximum rainfall due to Typhoon Hagibis. The velocity and water depth were estimated using rational runoff and velocity formulae. Consequently, more than 30% of the 86 sloping roads described in the hazard map were determined to be unsuitable as evacuation routes, and a positive correlation was observed between risk and upstream areas. A simple evacuation risk assessment of a sloping road with water flow can be performed by calculating the fluid force using the estimated velocity and water depth.