Urgent Issues and New Suggestions for Geo-disaster Prevention in Japan

Following the devastating damage caused by the heavy rains in western Japan in 2018, the Japan Geotechnical Society compiled and published recommendations for future disasters. This report introduces an outline of the recommendation on slope disasters. In particular, the recommendation emphasises the need for measures to evacuate residents from dangerous places before a disaster occurs. For this purpose, it is noted that it is important to identify potentially dangerous places and their characteristics in the long term based on past disaster information and to inform the residents of the identified areas. As a pioneering effort to achieve this recommendation, this paper describes the results of research conducted in Yamaguchi, Hiroshima, Tokyo, and Kumamoto in Japan, to clarify the frequency of the occurrence of debris flows and its utilisation measures. The main result is that debris flows occur once every few hundred years in weathered granite areas, whereas volcanic ash areas experience even more frequent debris flows than granite areas.