Process analysis and hazard prediction are essential for the prevention and mitigation of debris-flow hazards in mountainous areas. Many villages and ongoing infrastructure projects in China are vulnerable to large debris flows during heavy rainfall or glacier lake outbursts. Without emergency management planning, such contingencies can lead to extensive loss of life and egregious property damage. In the eastern Qinghai-Tibet Plateau area, debris-flow disasters are a common phenomenon. Taking Ridi Gully in the Sichuan Province of China as a case study, we analyzed the process of debris-flow events by running a dynamic erosion model. Because of the dynamic nature of the process, we needed to take into account many variables. Some of these variables include strong erosion in the origin area, scouring and downward erosion in debris-flow path, and siltation in accumulation area. Subsequently, we analyzed the elements underlying the hazard formation conditions and proposed a systematic and quantitative method of debris-flow hazard prediction based on kinetic energy and flow depth. Finally, we predicted the hazard and damage potential induced by the debris flow triggered by a 100-year and 200-year return period precipitation in Ridi Gully. The simulation results indicate that debris flow will cause great damage to the Sichuan-Tibet railway (or highway) and the residential area on the alluvial fan. This strongly suggests that, given the high level of debris-flow hazard predicted, the proposed method may serve as pertinent and timely support in planning measures to prevent or reduce the debris-flow hazard, both in the eastern Qinghai-Tibet Plateau area and beyond.
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