Abstract:

Taking the Yazhagou debris flow in Jiuzhaigou earthquake area of Sichuan as an example, the outbreak features, the critical rainfall and the origin are studied in detail through geological surveys and historical data analysis. Based on the analysis of the formation cause, the corresponding prevention and control schemes are proposed. The results show that the debris flow is featured by being concealed, sudden, and destructive, with strong sediment transport capacity. The critical rainfall of debris flow outbreak is only half of that before the 12^th May Wenchuan Earthquake, and no debris flow was reported in this area since 2014, indicating that the critical rainfall has a gradual recovery trend. Short bursts of heavy rainfall, deep-cut trough-type material supply, and elevated-steep topography are the root causes of the debris flow outbreak. The debris-flow genetic model includes the components of rainfall seepage, saturated rock and soil, mountain flood impact, deep-cut trough, headward erosion, scour erosion, bank erosion collapse, suspension and rolling. Controlling of Yazhagou debris flow in the earthquake area requires the protection standard and optimization of the control structure. Effective prevention and controlling method require mainly source control supplemented with debris obstruction. Our findings provide reference for the prevention and early warning of similar debris flows across the region.

Key words: deep-trough debris flow, genetic model, outbreak feature, critical rainfall, Jiuzhaigou area