The entrainment effect of a debris avalanche on the erodible substrate in the presence of water flow

Debris avalanches generally entrain the erodible deposits on their runout path, which can greatly influence their movement process, particularly in the presence of water flow. To study the entrainment effect of debris avalanches, physical modeling experiments were conducted that considered the impact of hopper elevation, the grain size of substrate materials and water flow. The experiment results indicate that the materials entrained by a debris avalanche increase with an increase in elevation of the hopper and particle size of the substrate materials in the rear region of the substrate. The presence of water flow can magnify the entrainment effect and enhance the mobility of the debris avalanche. However, the effect of water flow on the entrainment effect is significantly related to the grain size of the deposits. With a decrease in grain size, a water stream is easier to generate, which can cause intense scouring of the substrate materials and enhance the mobility of the mixed flow of debris and entrained deposits, ultimately leading to a greater affected area.