2004年台風10号に伴う豪雨により徳島県那賀川流域で発生した斜面崩壊の地質・地形的特徴

Many slope failures and debris flows triggered by heavy rainfall associated with Typhoon 0410 (Namtheun) occurred in Naka-gawa area, Tokushima, Japan on July 31st to August 1st, 2004. Many slope failures occurred at steep mountain slopes, which consist of greenstones, phyllites and schistose sandstones of accretionary complex. The greenstones are weathered to blocky fragments. This factor seems to be the major cause of slope failures of weathered greenstones. Deformations of foliated sedimentary rocks by gravitational mass rock creep are observed in source area of slope failures. Mass rock creep makes various kinds of non-tectonic structures, and degrades mountain slopes to make favorable conditions for slope failures caused by heavy rainfall.