安宁河上游冷渍沟泥石流特征及其发展趋势

冷渍沟是安宁河上游左岸的一级支沟，沟内发育了一大型滑坡 碎屑流，为后续泥石流活动提供充足的松散物质来源。为了研究冷渍沟泥石流的危害特征，在野外调查和实地勘测的基础上，分析了泥石流的形成背景条件及其特征，探讨了泥石流的发展趋势，提出了相应的泥石流防治对策。研究表明，冷渍沟泥石流属于过渡性（亚粘性）高频大规模泥石流，泥石流成灾速度快，危害严重；百年一遇的泥石流容重为21 t/m3，五十年一遇的泥石流容重为20 t/m3，二十年一遇害泥石流容重为19 t/m3，相应的峰值流量分别为12768、8171和3818 m3/s。在常态下，冷渍沟泥石流的发生频率和规模会逐渐减小；但如果近期遭遇强震或者暴雨，一旦滑坡失稳堵塞沟道，将会暴发大规模泥石流，很容易堵断安宁河，对上下游造成严重危害。因此，建议在该流域布设必要的泥石流防治工程；同时加强对沟道两岸和滑坡稳定性监测，做好泥石流发生的监测预警工作

CHARACTERISTICS AND DEVELOPMENT TRENDS OF DEBRIS FLOWS OF LENGZI GULLY IN THE UPPER ANNING RIVER,SOUTHWEST SICHUAN,CHINA

Lengzi gully is the first order branch of Anning River.There is a large-size landslide in the gully,which provides debris flows with sufficient loose materials.To study the debris flow hazard characteristics,researches were conducted on the formation conditions and development trend of debris flows in the gully based on the field survey,and the countermeasures for debris flow mitigation were also proposed.Results indicated that the debris flows are characterized by low viscous,high frequency,large-size and severe risks.The densities of debris flows were 2.1 t/m3 of 100-year return period,2.0 t/m3 of 50-year return period and 1.9 t/m3 of 20-year return period and the corresponding peak discharges were 127.68,81.71 and 38.18 m3/s,respectively.In normal situation,the frequencies and scales of debris flows will decrease gradually in Lengzi gully.But if strong earthquake or heavy rain happens in this area,large-size debris flows will occur,which will largely block the main river and cause serious harm to upstream and downstream.Accordingly,we suggest that the debris flow control projects should be laid and stability monitoring and warning system of landslide and both sides’ slopes of the gully should also be conducted in the valley.