Sensitivity analysis of debris flow to environmental factors: a case of Longxi River basin in Dujiangyan, Sichuan Province

Debris flow is a common geological hazard in mountainous areas. In order to quantitatively study the sensitivity of disaster-causing factors of debris flow and determine the weight coefficient of each hazard factors. The field investigation, mathematical statistics and analytic hierarchy process were used to study qualitatively and quantitative weights of hazard-causing factors in Longxi River Basin. The results show that:(1) the qualitative analysis between the occurrence of debris flow disasters and the susceptibility factors of hazards are as follows:the watershed area is less than 1 km², the height difference is within 200 to 400 m, the distance from the fault is 0 to 2 km, and the slope of the slope is 30°~50°, the lithology is sandstone, the vertical ratio drops between 400‰ to 600‰, etc., the occurrence of debris flow disasters is well relevance to its main disaster-causing.(2) Four primary factors, including historical factor, topographic factor, geological factor and rainfall factor, as well as 14 secondary factors, such as watershed area, elevation, relative elevation difference, longitudinal slope ratio and stratigraphic lithology, are selected to establish the analytic hierarchy process model and the calculation judgment matrix. Obtains the weight value of disaster-causing factors on debris flow occurrence, which indicates that the four factors of rainfall, watershed area, stratigraphic lithology, and aspect ratio are the most sensitive to debris flow occurrence. This conclusion provides some data reference significance for the susceptibility, risk, and risk assessment of debris flow in the region.