小江流域是我国乃至世界暴雨泥石流最发育的地区,其中的蒋家沟又是小江流域活动最强烈的泥石流沟。2001年7月8日蒋家沟暴发了大规模的泥石流,泥石流进入小江后淤积成坝,导致小江堵塞,并造成一定灾害。近期的地震活动、前期大量降水和当日长历时连续降雨是该次泥石流形成的主要原因。原导流堤溃决后形成蒋家沟泥石流运动方向与小江水流方向垂直,高粗大颗粒含量、高容重和大流量的有机组合是泥石流停淤成坝堵塞小江的主要因素。

Xiaojiang river, a branch of Jinsha river, is an area with most developed debris flow valleys in China and even in the world, and the debris flow of Jiangjiagou valley is most active in Xiaojiang basin. A large scale debris flow continuing 15 hours occurred in Jiangjiagou valley. An amount of sediment transported by the debris flow deposited in the stream outlet and jammed the stream of Xiaojiang river then made some disasters. Themain origins of the debris flow event were recent earthquake activity, a great deal of antecedent rainfall and long time continuous intraday rainfall. It is the main reason that the included angle betw een the steams of Jiangjiagou valley and Xiaojiang river was changed to 90°due to the old diversion dike break, and that the high content of coarse granule, high volume weight and large discharge of debris flow appeared in synchronously. Rebuilding the diversion dike to change the include angle, returning land for farm ing to forestry to recover the environment then change the condition of debris flow initiation are effective measures for preventing Xiaojiang river stream jammed by debris flow of Jiangjiagou valley.