ON INCREASING HEAVY PRECIPITATION DISASTER RISKS IN KYUSHU REGION AND THE MEASURES

Abstract

 Early July in 2020 corresponding to the end of rainy season, lots of warm air containing massive water vapor flowed into the seasonal rain front being stationary over Kyushu Island, located at western part of Japan through the so-called “atmospheric river” from Indian Ocean and East China Sea. Therefore, large scale “Senjo-Kousuitai” (quasi-stationary band-shaped precipitation system) generating over basins of Kuma River and Chikugo River which are class A rivers in Kyushu Region caused serious flood and sediment disasters. Global warming has enlarged Senjo-Kousuitai, and has become Typhoon gigantic and slow-moving. Geographical features in Kyushu Island increases large scale flood disaster risks in each river basin. As the countermeasure for future large scale flood disaster in Kuma River basin with a main branch, Kawabe River, a hybrid type large-sized dry dam is recommended in order to achieve both natural environment preservation and flood disaster prevention.