The Effect of Surface Layer Thickness in a Wide-Area Simulation in Different Models: Susceptibility Mapping of Rainfall-Induced Landslide
Akino Watanabe*1,, Akihiko Wakai*1, Takatsugu Ozaki*1, Thang Van Nguyen*1, Takashi Kimura*2, Go Sato*3, Kazunori Hayashi*4, and Nanaha Kitamura*1
1-5-1 Tenjincho, Kiryu, Gunma 376-8515, Japan
*2Ehime University, Ehime, Japan
*3Teikyo Heisei University, Tokyo, Japan
*4Okuyama Boring Co., Ltd., Miyagi, Japan
In recent years, sediment disaster has frequently been caused by heavy rainfall and has cost many human lives and great property losses. To estimate such risks, Wakai et al.  proposed a simplified prediction method to calculate the variation of groundwater levels in natural slopes both at the time of rainfall in wide areas and in real time. To calculate the variation of groundwater levels using this method, the slope conditions (such as material constant and initial conditions) must be determined in advance. This study takes the 2017 heavy rainfall in Northern Kyushu as an example to analyze surface layer thickness, one of the slope conditions that most significantly influences slope stability, over wide areas. The findings reveal that the prediction of slope failure distribution differs depending on how the surface layer thickness and sliding surface are determined.
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