[H-DS11] Geohazards in humid, tectonically active countries and their precursors

[HDS11-P07] Predicting location, magnitude, and timing of rain-induced shallow landslides: a test of accuracy and precision for the case of northern Kyushu disaster in 2017

*Yuki Matsushi¹ (1.Disaster Prevention Research Institute, Kyoto University)

Keywords:shallow landslide, soil, shear strength, rainwater infiltration, hillslope stability

This study examined a methodology for predicting location, magnitude, and timing of rain-induced shallow landslides for the case of disaster caused by a rainstorm in northern Kyushu on 5th July 2017. In our approach, simulation of soil production and transport on a digital terrain model provides the thickness of sliding material on hillslopes, which is validated by a ground-based survey in the actual terrain in a selected watershed. The shear strength of the bulk soil was evaluated by direct shear tests using undisturbed specimens, and quantification of soil reinforcement by tree roots through an in-situ survey at soil pits. Hydrological monitoring was carried out at a representative hillslope for modeling the fluctuation in subsurface pore-water pressure by rainwater infiltration. By coupling all of those data and modeling, we analyzed the hillslope stability on geographic information systems, and then compared the output with a landslide inventory map to confirm the accuracy and precision of the prediction.