Two-dimensional numerical model for debris flows in the Jiangjia Gully, Yunnan Province

Debris flows are recurrent natural hazards in many mountainous regions. This paper presents a numerical study on the propagation of debris flows in natural erodible open channels, in which the bed erosion and sedimentation processes are important. Based on the Bingham fluid theory, a mathematical model of the two-dimensional non-constant debris flow is developed. The governing equations include the continuity and momentum conservation equations of debris flow, the sediment convection-diffusion equation, the bed erosion-deposition equation and the bed-sediment size gradation adjustment equation. The yield stress and shear stress components are included to describe the dynamic rheological properties. The upwind control-volume Finite Volume Method (FVM) is applied to discretize the convection terms. The improved SIMPLE algorithm with velocity-free-surface coupled correction is developed to solve the equations on non-orthogonal, quadrilateral grids. The model is applied to simulate a debris flow event in Jiangjia Gully, Yunnan Province and to predict the flow pattern and bed erosion-deposition processes. The results show the effectiveness of the proposed numercial model in debris flow simulation and potential hazard analysis.