DEVELOPMENT OF A FRAMEWORK FOR COMPOUND FLOODING RISK ASSESSMENT DUE TO TSUNAMI AND HIGH RIVER FLOW

Composite flooding hazards were evaluated using a tsunami–flood coupled model for Mikawa Bay, Aichi Prefecture. Using eleven tsunami patterns provided by the Central Disaster Prevention Council, we performed calculations for 55 events considering five river-flow patterns (base runoff, 25, 50, 75, and 100percent) in a tsunami scenario based on the most recent flood case of June 2023. The water levels of six rivers calculated using the distance from the river mouth were at peak on the river mouth when flooding was small (base runoff, 25percent), and the maximum level occurred approximately 2.0 km upstream from the river mouth. Additionally, the characteristics of water level rise between the rivers in response to the composite hazard (difference between the most recent flood and base runoff) were at peak (+4.8 m) in the Otowa River and at minimum (+1.2 m) in the Umeda River. Based on the above measurements, we clarified the influence of river flow on tsunami and spatial characteristics.