Abstract
The archipelago in Japan situates in unstable subduction zone, where earthquakes and volcanic activities frequently occur. Mountains have been continuously subjected to upheaval under the tectonically active stress since the quaternary era. Scoring and erosion frequently occur in river banks and slopes due to heavy rains and river flows, which form “knick lines” in terms of geomorphology. Slope rock mass also become fragile due to weathering in the long term. These specific geological and geomorphological conditions in Japan, in couple with wet climate conditions, induce erosion in river basins and mass movement such as landslide and failure.
This paper describes several phenomena of erosion process including river capture in neighboring basins, and gravitational deformation of rock slopes which may indicate signs of landslides.
