Landform analysis of slope movements using DEM in Higashikubiki area, Japan

Abstract

Various numerical analyses using 25 m-grid DEMs were compared with rasterized slope movement distribution maps and geological maps of the Higashikubiki area in Niigata Prefecture, Japan. Slope movement distribution maps included five classes: “stable slope”, “landslide mass”, “landslide scarp”, “collapse scarp” and “crack”. Their statistical characteristics were clarified by numerical landform analyses for each lithology. Frequency distributions of slope angle were nearer to a normalized distribution for landslide masses than for stable slopes. From the difference of mean slope degrees of landslide masses and that of stable slopes, it was estimated that the smallest slope angle at which landslides occur is approximately 10° for sandy formations. Moreover, mean values of slope angle in the total study area and total landslide masses were both approximately 14°. For sedimentary rocks, graphs of mean slope for each elevation zone of landslide mass and stable slope were parallel, and slope angle did not increase above approximately 100–160 m. For landslide masses and collapse scarps, the relationship between slope and convexity or roughness showed a regular relation closely resembling linear or quadratic function.