Topographic Characteristic of the Rainfall-Inducing Landslide in Slate Stratum—Case of Ai-Liao Catchment, South Taiwan

This paper describes the topographic characteristics of the landslides induced by 2009 Typhoon Morakot in Ai-Liao catchment, a slate geologic region. The topographic analysis on DEM shows 52 % of landslides were larger than 10 ha, the average slope of landslides was 20°–40°, and 81 % of the landslides were located at the hillside or the toe of slope. This was related to washing away by the river. For a massive landslide, the analysis results also demonstrate that a certain degree of deflection usually occurs before a sliding initiation. This suggests the deformation of a massive landslide is progressive. Moreover, when the profiles curvature of a landslide are close or above the curvature 1 × 10−4 (l/m), the sliding possibility of a massive landslide will increase.