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2011-06-06贵州省望谟县北部普降百年一遇暴雨,引发大规模群发性泥石流灾害,给当地居民生活及交通造成严重损害。其中以打蒿沟泥石流灾害尤为突出,该流域内支沟发育,沟床比降相对较缓,但陡峻的岸坡和较大的汇水面积为泥石流的发生提供了良好的水动力条件。打蒿沟地处碎屑岩发育地区,松散堆积体较厚,并受岸坡坡度影响浅层滑坡发育,现场调查共19处。另外流域内人为破坏严重,村民沿沟垒筑大量梯田也为泥石流活动提供了特殊的人工物源。通过对其4条支沟的研究发现,泥石流形成特征并不一致,其中坡度较缓的2#支沟浅层滑坡发育,为浅层滑坡型泥石流;而坡度较陡的其他3条支沟浅层滑坡发育较少,以沟床物源为主,为沟床启动型泥石流。通过对沟道两侧斜坡坡度的调查统计和分级得出流域内25°～40°的岸坡最易形成浅层滑坡,且当山坡呈上缓下陡时,更利于滑坡的形成。打蒿沟在强降雨条件下依然可暴发泥石流,规模会有所减小,但在类似2011-06-06这类稀遇暴雨作用下仍可造成较大危害。
2011-06-06 Heavy rainfall in the northern part of Wangmou County, Guizhou Province, caused a massive massif debris flow disaster, causing serious damage to the lives and traffic of local residents. Among them, the Dalihaogou debris flow disaster is particularly prominent. The development of branch ditches in the drainage basin is relatively slow, but the steep bank slope and larger catchment area provide a good hydrodynamic condition for the occurrence of debris flow. Beidiaogou is located in the clastic rock development area, loose accumulation of thick, and by the impact of bank slope shallow shallow landslides, a total of 19 field surveys. In addition, the man-made damage in the basin is serious, and the villagers build a large number of terraces along the ditch to provide special artificial sources for debris flow activities. Through the research on its four branch ditches, it is found that the formation characteristics of debris flow are inconsistent, in which the shallow landslide in No.2 # branch with a gentle slope is developed as a shallow landslide type debris flow; while the other three branch ditches shallow in steep slope Less landslide development, mainly to the source of the ditch bed, ditch bed start debris flow. Through the survey and grading of slope slopes on both sides of the channel, it is concluded that the shallow landslide is most likely to be formed in the bank of 25 ° ~ 40 ° in the basin and more conducive to the formation of landslides when the slope is slowly and steeply sloped. Miaoli ditch in the heavy rainfall conditions may still be debris flow, the size will be reduced, but in 2011-06-06 such a rare rainstorm can still cause greater harm.