“5·12”汶川地震后北川苏保河流域泥石流危害及特征

Debris Flow and Its Characteristics of Subao River in Beichuan County after "5·12" Wenchuan Earthquake

汶川8级地震直接引发了大量的崩塌、滑坡等次生山地灾害,为泥石流提供了丰富的物质来源,灾后遇高强度降水,已引发大规模的次生泥石流灾害,严重威胁灾民安置点和灾后重建场址。以北川苏保河流域为例,分析了泥石流形成的地形地貌条件、松散固体物质条件和降水条件,总结了苏保河流域泥石流的危害和特征,在此基础上,通过形态调查法和雨洪法对泥石流流量的计算进行了对比分析。结果表明:地震后苏保河流域演变为泥石流多发区域,泥石流将会危害人民生命财产安全、灾后抢险救灾公路和人类生存环境;苏保河流域泥石流具有呈群发性,危害范围大、密度高,搬运能力强、激发泥石流的雨量相对偏小、多灾种复合性的特征;地震后,由于强震引发松散固体物质的剧增、地表植被破坏引起径汇流条件的变化、沟道性质的变化及沟道内形成的多级堵塞,使泥石流的规模增大。

＂Wenchuan Earthquake＂ caused a lot of secondary disasters,such as,collapse and landslide,which provide rich material sources for debris flow. The high-intensity rainfall after the disaster has already induced large-scaled debris flows,which threatens victims＇ resettlement spots and reconstruction spots greatly. This paper takes Subao River basin in Beichuan county as an example,analyzes topography and geomorphology conditions of forming debris flow,loose solid matter conditions and precipitation conditions,and summarizes the damage and characteristics of debris flow in the Subao River basin,on the basis of which,the calculation of the flow of debris flow is compared and analyzed by means of morphology investigation method and rain flood method. The result shows that Subao River basin in Beichuan is a region with frequent debris flows and debris flows will threaten people＇s life and property safety,emergency rescue and disaster relief road and human beings＇ living environment. Subao River debris flow has the characteristics of group-occurring,large-ranged damage,high density,strong transport capacity,comparative small rainfall that induces debris flow and many disaster types. After the earthquake,since huge increase of loose solid material,runoff and convergence change due to destroyed vegetation by earthquake,property change of channel and many blockages formed in the channel,the scale of debris flow will increase.