Hydrodynamic and topography based cellular automaton model for simulating debris flow run-out extent and entrainment behavior

As for late, studies have indicated that cellular automaton (CA) models are among the most effective solutions for simulating the extent of debris-flow run-out. However, it is currently difficult to effectively simulate both the inundated area and the erosion pattern of the debris flow process. This difficulty is caused by the lack of detailing regarding debris flow hydrodynamics as the primary concern of most CA-based models is the topographic gradient of the gully. In this study, we propose a two-dimensional Monte Carlo simulation-based CA model with hydrodynamic methods describing debris-flow behavior to address these problems. Herein, a topography function concerning slope gradient and bed roughness, and a persistence function regarding flow inertia, are combined to improve the flow routing algorithm for better determining the run-out extent of debris flow. Hydraulic links and discharge exchange between neighboring cells using sink-filling approach, as well as the bed sediment entrainment function, are incorporated into the CA model to describe the mass migration process along the flow path. To verify the performance of our proposed model, we further select the 2010 Yohutagawa debris flow event in Japan as a case study. The results indicate that the proposed model better simulates the complex dynamic process of debris flow.