基于遥感影像的四川石棉“7·4”后沟泥石流形成机理与堵河过程分析

Mechanism of formation and blocking river of debris flow disaster on 04 July,2013 in Hougou of Shimian,Sichuan using remote sensing images

本文以2013年7月4日四川石棉县后沟堵河型泥石流为研究对象,通过泥石流堵河前后对比研究、前期与当日降雨分析、理论计算,认为后沟泥石流为强降雨自然诱发、矿渣物源补给的复合型泥石流。后沟泥石流的启动过程主要表现为:强降雨→启动点产生→沟道侵蚀、拉槽→沿程流量加大→矿渣物源参与→规模突增→淤积与下切交错→堵塞楠桠河。通过灾后的实地调查,后沟泥石流堵断楠桠河溃坝后,在堆积区形成2个堆积扇和3个对冲淤积点,保存着泥石流顶冲对岸形成堰塞体的形态特征,具有典型泥石流堵河特征。通过经验公式计算,后沟堵河程度在堵河可能性小和严重堵塞之间,与历史频率、实地调查、遥感分析具有较好的适应性。

Heavy rainfall occurred in the county on 04 July,2013 in Shimian,which caused the outbreak of the debris flow,The mass of debris flow disaster caused serious human and property losses. Select the debris flow in Hougou as the research object,by comparative analyzed The theoretical calculation of the critical value of the start of the debris flow in the Hougou meteorological rainfall data; remote sensing image in the region before and after the debris flow,the debris flow is a typical slag type induced by heavy rainfall. The starting process of debris flow expressed as strong rainfall→ Hydrodynamic enhancement,soil saturation and anti-slip capability weakened→ start point generating→ gully erosion→ flow increase→ slag provenance participation→scale sudden increased→ deposition and cutting→ blocked Nanya River. Through field survey we found,after the debris flow blocking off Nanya River,forming 2 stacked fan and 3 points in the accumulation area of erosion and deposition. 3 points of erosion and deposition kept rushing across the formation of morphological characteristics of debris flow damming body. Calculation by empirical formula,the possibility of blocking the river between small and serious blockage,agree with field survey and remote sensing analysis.