汶川地震区泥石流危害道路的定量分析——以汶川县肖家沟为例

为适应震后3年泥石流大规模频发的严峻形势,满足灾情预测评估的需要,以汶川县省道303沿线肖家沟为例,建立了震后泥石流危害道路的定量分析方法.通过现场勘察并结合RS、GIS技术,分析了震后肖家沟泥石流发育的环境地质背景、流域面积、沟床比降以及泥石流性质等基本特征；采用雨洪法和配方法计算肖家沟泥石流一次过程总量,作为泥石流堆积量预测值；通过回归分析,获得了泥石流堆积体危害范围的计算公式,以确定泥石流的平均堆积厚度、长度和宽度；最后,采用几何概化方法,就肖家沟泥石流对沿河道路的危害程度进行了量化分析.结果表明,在50年一遇的降水频率下,肖家沟泥石流一次过程总量为41万m3,道路完全掩埋,并堵断渔子溪,计算结果与实际情况一致.

Quantitative Hazard Assessment of Road Debris Flow in Wenchuan Earthquake Area: A Case Study of Xiaojia Ravine in Wenchuan County

A quantitative assessment method of debris flow hazard to roads in Wenchuan earthquake areas was established based on the case study of Xiaojia ravine to assess serious debris flow disasters happening frequently in 3 years after the Wenchuan earthquake.The environmental and geology background and the basic parameters such as the area and gradient of Xiaojia ravine were anglicized through a field investigation and using the RS and GIS technologies.The total amount of once debris flow process calculated by the rain-storm and flood method and the method of completing the square was taken as the pile quantities.Pile scope parameters,including average pile thickness,length and width,were estimated by a regression expression derived from field investigation data.Then the damage degree of debris flow to the roads beside Yuzi river was calculated quantitatively by the geometric generalization method.The research shows that the total amount of once debris flow process is 41×104 m3 under rainfall that occurs once every 50 years,the roads will be completely buried and the river blocked by the debris flow.The above results are basically coincident with the actual hazard situation.