STUDY ON INFLUENCE OF ROADS ON DEBRIS FLOWS OCCURRED DUE TO 2018 JULY HEAVY RAIN

Abstract

 Due to 2018 July heavy rain, debris flows occurred in mountainous residential area and caused serious damage in western Japan. Mountainous streams where debris flows occur extending from valley exit are often concealed with culverts upstream of the residential area. In Kobe City and Hiroshima City, culverts existed upstream of the residential area were blocked with sediment and debris flows moved down along the roads connected to culverts. Furthermore, the roads slope were steep, and debris flow in Kobe showed high mobility due to containing fine sediment from granite sediment, sediment have extended widely in residential areas. In this study, we aimed to consider the disaster situation focusing on culverts and roads existing on residential area from field surveys. And we also conducted numerical simulation to describe the disaster scenario and to consider and to propose safe landuse in residential area.