昭和28年有田川水害で発生した深層崩壊の地質地形学的素因について

Abstract

To reveal the geological and geomorphological causes of deep-seated catastrophic landslides (DCLs) by heavy rainfall in the 1953 Aridagawa disaster, detailed geological mapping and geomorphological analysis using 1-m DEMs were undertaken in the upper reaches of the Arida River in the Kii Mountains. This area is underlain by the Cretaceous accretionary complex, consisting of sandstone dominated alternating beds of sandstone and shale and their broken formation. As a result, southward dipping low-angle faults, shear planes of broken formation with laumontite veins and the Yanase fault formed the failure surfaces and most of the DCLs were distributed along the convex slope breaks, undercut slopes and ridge lines with deep weathered rocks.