甘孜县四通达沟泥石流的形成特性

川西高寒地区泥石流的形成机理、运动过程、动力特性,受高原地形地貌、地质构造、地层岩性、气候条件等影响具有独特性。以四川省甘孜县四通达沟泥石流为例,通过对泥石流清水汇流区、物源区、堆积区的详细调查、测绘和泥石流堆积物样品分析,研究了高寒高海拔地区泥石流的成因和特征,综合分析了泥石流的动力特性。研究表明:(1)流域地形高差大,沟道坡降比高,为泥石流形成提供了良好的地形条件;(2)流域汇水面积大,易形成短时暴雨的高原气候为泥石流的形成提供了水源条件;(3)该流域发育于川西高寒地区,处于寒温带、亚寒带、寒带等气候变化带,立体变化显著。强日照,大温差的气候条件使得岩石差异风化、冻融作用强烈,以及受鲜水河断裂带的影响,使岩体破碎,土体结构松散,为泥石流的形成提供了丰富的物源。

Formation Characteristics of Sitongda Valley Debris Flow in Ganzi County

The formation mechanisms, movement processes, and dynamic characteristics of debris flow in the Western Sichuan Plateau, a high altitude and cold climate area, are unique because of the effects of landform, geological structure, ormation lithology and climate conditions. The areas of water convergence, provenance and accumulation of debris flows in the Sitongda Valley, Ganzi County, Sichuan Province are investigated by field investigation, mapping and sieving test to determine their formation mechanisms and dynamic characteristics. Results indicate that: (1) There are a big difference in elevation of basin terrain and a high ratio of channel slope, which provides terrain conditions for formatting debris flow. (2) Because drainage area of debris flows is wide, short-term rainstorm in plateau climate is able to provide adequate water supply. (3) Rivers develop in more than 3 000 m altitude areas, located in a climate change belt within cold temperate, subfrigid and frigid zones. Rock mass is fractured and soil structure is loose, caused by the climate condition of strong sunshine and large difference temperature that makes rock contrast weathering strong, as well as the influence of Xianshuihe fault zone. The fractured rock mass and loss soil structure provide rich source for the formation of debris flow.