【摘要】 汶川大地震的同震次生灾害以滑坡、崩塌居多,泥石流相对较少。但地震导致滑坡、崩塌为震后泥石流提供了极为丰富的物质来源,使得地震灾区在一年多的时间里已经多次暴发了大面积的泥石流。以北川地震重灾区的苏宝河和魏家沟流域为研究区域,通过野外实地考察、遥感图像分析、历史资料对比等方法,概括总结出受地震强烈影响区域的泥石流具有成因多样、时间同步、颗粒粗大、多灾种复合、空间近似对称和小沟大灾等特征。并提出了"面上监控为主、点上工程为主、分类防治和开展风险评估"的减灾对策。更多还原

【Abstract】 Coseismic geologic hazards of the Ms 8. 0 Wenchuan Earthquake included a great amount of landslides,rockfalls and avalanches,but few debris flows. However,numerous mass movements such as landslides and avalanches are becoming a plentiful mass source for the formation of debris flows,and many debris-flow events have occurred widely since the earthquake,especially in the meizoseismal area. In this paper,debris-flow ravines at Subaohe and Weijiagou rivers in Beichuan’s Meizoseismal area,southwestern China are studied by field investigation,remote sensing image interpretation and historical data analysis. It is summarized that the formation of these debris flows in the study area can be mainly divided into three classes,viz. direct mobilization from landslide,erosion of unstable slope,and outburst of blocked flood. Other disasters such as flood,landslide,and avalanche were accompanied with the debris flows. The distribution of grains in the debris deposits concentrates on sand,cobble and boulder. The events were closely synchronous because they were triggered by the rainstorms on September,23 ～ 24,and the locations of the ravines show some kind of space symmetry. Another notable feature is that the magnitude of debris flows is large even for those ravines with small catchment area. Finally,four countermeasures mitigating debris flows are proposed against the debris-flow hazards,which can be practically applied to debris-flow prevention.更多还原