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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。
In this paper, the clogged debris flow in the back ditch of Shimian County in Sichuan Province was investigated on July 4, 2013. Based on the comparative study of pre-and post-runoff debris flow, rainfall analysis and theoretical calculation at the pre- and present day, the debris flow in the posterior gully was naturally induced by heavy rainfall. Source of supply of complex debris flow. After the gully debris flow start-up process is mainly manifested as: strong rainfall → start point → channel erosion, pull the tank along the flow increases → slag material source → → sudden increase in scale sedimentation and cut staggered → plug Nan Nanhe. After the post-disaster field investigation, the Hougou debris flow blocked Nan Nanhe dam, forming two accumulation fans and three hedge silt accumulation points in the accumulation area, preserving the morphological characteristics of the dam body formed on the opposite bank of the debris flow, with typical debris flow Plugging the river features. According to the empirical formula, the degree of plugging the river after the ditch is between the possibility of blocking the river and the serious blockage, and has good adaptability with the historical frequency, field investigation and remote sensing analysis.