Comprehensive modelling of runoff-generated debris flow from formation to propagation in a catchment

This study aimed to develop an integrated model of the runoff-generated debris flow that considers the initial conditions, movement mechanisms, and entrainment effect. The study focused on the formation and propagation processes of debris flow within a catchment, and the process is divided into three stages: rainfall infiltration, runoff, and debris flow routing. Soil saturation, rainfall, and entrainment are the main factors that influence the debris flow formation and propagation processes. Existing models for each stage, including Richards’s equations, shallow water equations, and two-phase debris flow equations, were coupled. The tridiagonal matrix algorithm and finite volume method were applied to solve these equations. Finally, several experimental cases and the 2010 debris flow event in the Hongchun catchment in China were simulated by using the proposed model. The results showed that the proposed model could effectively describe the behaviours of each stage during the debris flow formation and propagation processes. Although several aspects of the model require further improvement, the physical-parameter-based prediction of runoff-generated debris flows from formation to propagation is effectively performed by the model.