Fig. 6

Entrainment process of the debris avalanche on the bed materials: a the debris avalanche encounters erodible substrate; b the bed material is sprayed by the high-speed debris because of the impact; c, d the bed materials are scoured by the motion of the debris and gradually cut in deep; e shallow erosion occurs and compression ridge forms because of collision and compaction; f a thin layer of substrate materials is activated to move forward under the shear effect of upper motion debris