斜面(4)

[III-32] Threshold of soil water index regarding landslide occurrence in Ryoke granite areas in Ehime Prefecture during the July 2018 Heavy Rain Event

〇Shinichiro Mori¹, Kohei Ono¹ (1.Ehime University)

Keywords:landslide, soil water index (SWI), threshold, geology, Ryoke granite, July 2018 Heavy Rain Event in Japan

During the July 2018 Heavy Rain Event, approximately 1,000 landslide disasters occurred in Ehime Prefecture. In particular, about one-third of them occur in the granite areas of the Ryoke belt. So far, it has been considered that the judgment of landslide disasters based on the soil water index (SWI) does not depend on the geology. However, this paper shows that the threshold value differs depending on the geology based on the rainfall characteristics and the time of occurrence of landslides on the snake curves in the hourly rainfall-SWI plane.