Numerical simulation for runout process of debris flow using depth-averaged material point method

Debris flows, i.e., combined flows of watery mud, chunks of boulders, trees, etc., can be extremely destructive to life and property and can exhibit complicated mechanical features. These complicated features of heterogeneous debris-flow surges can be rationally modeled by considering the rheological behaviors of solid, liquid, and interaction-force phases. Herein, we present the simulation results obtained using a numerical method for a runout process of debris flows based on the depth-averaged equation of motion implemented with the material point method. This method enabled us to describe the debris-flow behaviors in a more adequate manner than previous methods, by simulating debris flows using a depth-averaged model. The simulation results were verified by comparing them with the results of flume tests on dry and wet sand flows. The test results were calibrated to identify the key parameters for simulating the runout process of soil flows. In addition, a real debris-flow event was simulated, and important features of the simulated debris flow, i.e., the geographical dimensions of the depositional zones, conformed well to the observed dimensions of the real debris flow.