[H-DS11] 湿潤変動帯の地質災害とその前兆

[HDS11-P07] 表層崩壊の場所，崩土量，発生時刻の予測: 2017年北九州豪雨災害に対する事後解析による確度と精度の検証

*松四 雄騎¹ (1.京都大学防災研究所 地盤災害研究部門 山地災害環境分野)

キーワード：表層崩壊、土層、せん断強度、降水浸透、斜面安定

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.