Characteristics and Formation Conditions of Debris Flows in Jushui River Basin, Anxian County, Sichuan Province

Jushui River is located at Northwest of Anxian County in Sichuan Province, which belongs to the epicenter area of the 2008 Wenchuan Earthquake. During the past five flood seasons, there are group-occurring debris flows with different scales every year at Jushui River. The debris flows happened on July 9 of 2013 is the most destructive, and has brought out huge damages to the area of Jushui River. In this paper, we discussed the characteristics, distribution and formation conditions of the debris flow in Jushui River on the basis of tracking investigation, topographic and rock information, and got some preliminary conclusions as listed below: firstly, the large elevation deviation, huge amount of unconsolidated sediments and intensive rainstorm in Jushui River area are beneficial conditions to the generation of huge and destructive debris flows; secondly, The debris flow mainly distributes in the area where shale, fractures exposed, as well as the areas with sharp terrain slope and elevation deviation; thirdly, the debris is characterized by its group-occurring, high frequency, density and transport capacity. The superposition of the disaster will increase the damage and destroy the road for emergency service.