The July 2020 Rainfall-Induced Sediment Disasters in Kumamoto Prefecture, Japan

Abstract

On July 4, 2020, heavy rainfall was observed in the southern part of Kumamoto Prefecture and the northern part of Kagoshima Prefecture. Due to heavy rainfall, floods and sediment disasters such as collapses and debris flows occurred predominantly in the Kuma River basin of Kumamoto Prefecture. We conducted field investigations at four sites in Ashikita Town and Tsunagi Town, Kumamoto Prefecture, where collapses and debris flows caused deaths. We also conducted field investigations in the Kawauchi River branch of the Kuma River, where vast amounts of sediment discharge caused damage to houses. The objectives of these investigations were to clarify the situation and mechanism of the disasters and to propose procedures to recover from the disasters. This report briefly summarizes the results of these investigations.