Collapsed material movement of deep-seated landslides caused by Typhoon Talas 2011 on the Kii Peninsula, Japan

抄録

Extensive research on landslide susceptibility and landslide-affected areas has been conducted, but many technologies still lack sufficient accuracy and information to predict the movement of collapsed material. Adequate disaster mitigation requires prediction of the movement type and travel distance of collapsed material from deep-seated landslides. This research aims to classify the movement type of collapsed material from deep-seated landslides and to clarify the topographic conditions that influence it. The research area is the Kii Peninsula, south-western Japan, which was severely damaged by sediment-related disasters triggered by Typhoon Talas in 2011. A digital elevation model and aerial photographs were used in ArcGIS analysis, and topographic characteristics were examined to find significant factors that influenced the movement of collapsed material. Collapsed material of deep-seated landslides formed two main outcomes, debris flows and landslide dams. Debris flows were likely in catchments of streams with gradient > 10°and inflow angle <60°. Landslide dams were likely in catchments of streams with gradient < 10°and inflow angle > 60°. Landslide dams with an upstream watershed exceeding 100 km² tended to remain for much shorter periods than those with smaller watershed. The equivalent coefficient of friction, representing the travel distance and degree of fluidization of collapsed material, could be used for predicting the deposition zone of collapsed material.