Disaster report of 2018 July heavy rain for geo-structures and slopes in Okayama

Abstract

In July 2018, heavy rain and a large amount of damage to geo-structures and natural slopes were reported in Okayama, Japan. In particular, in the area surrounding the Oda River System, 52 people drowned due to the breach of river banks. Besides the flooding of rivers, the earth-fill dams of many water reservoirs were damaged. The stability of the large number of earth-fill dams in the Setouchi area is very important. Heavy rain is often associated with the collapse of slopes. In Okayama, many shallow slope failures or debris flows occurred over a wide area, particularly in the western part of the prefecture. Through detailed investigations, the mechanism of this geo-disaster was clarified.