Calculation method for flow depth and velocity of debris flow based on hydrological-hydrodynamic coupling

Because debris flows in catchments are highly sudden and conventional forecasting approaches have difficulty achieving continuous dynamic simulation, this study developed a distributed dynamics calculation model for debris-flow processes (Distributed Dynamics Calculation Model, DDCM) based on the equivalence relationship between hydrological and hydrodynamic processes. The model integrates the Modified Soil Conservation Service Curve Number method (MSCS-CN), the Muskingum flow routing method, and the kinematic wave equation. Taking the Qinjiawan debris-flow catchment in Liangshan Prefecture, Sichuan Province, China, as the study area, the model achieved rapid simulation of the rainfall-driven evolution of debris-flow movement. The results show that the maximum error in flow depth was 0.029 m and the maximum error in flow velocity was 0.21 m/s, demonstrating the model's accuracy and physical reliability in initiation, evolution, and transport processes of debris flows. The proposed model can provide scientific support for real-time forecasting, risk identification, and disaster mitigation and prevention in debris-flow in small watersheds in complex mountainous regions.