Model of the landslide triggered by a debris flow (Sassa et al.). The process can be divided into three stages. At stage I, the displaced sliding mass slid in the source area of the landslide. At stage II, the displaced sliding mass quickly moved onto a deposit layer (with a slope angle of θ ) in front of the landslide at an angle of α.F
is the impact force from the displaced sliding mass on the deposit layer.h
is the depth of the new sliding surface in the deposit layer,hw is the height of groundwater table over the new sliding surface. At stage III, the impact force disappeared, and the displaced sliding mass moved together with the deposit layer. The upper left corner is a close-up of a column in stage II.