Study On Risk Assessment Of Debris Flow And Debris Flow Formation Mechanism Of Yaan City

In this paper, the study area is mainly about Lushan County and Tianquan County of Ya'an City, covering an area of about 3746.1km2.The main contents are following parts.(1)With comprehensive analysis of geological environment information and field surveys of Lushan and Tianquan County, we find that the debris flows are uneven spatial distributions. And the occurrence of debris flows are consistent with structure, heavy rainfall, etc. We come to know the formation mechanism of debris flow area. That terrain conditions in the region for the outbreak of debris flow provides the basic conditions.Tectonic and seismic makes rock crushing area, ditch the source rock and soil Slump and loosely packed in the channel and a channel source for the outbreak mudslides We prepared a rich provenance. Large catchment area and the debris flow gully longitudinal drop greatly outbreak provided the impetus conditions, huge floods so strong rainfall within a channel formed easily produce debris flows. Combined with the mountain of three concrete debris flow analysis Muan, gangou head, Ran Jiashan to determine the territory of debris flow Slump evolution- Storm debris flow.(2) During the outbreak of debris flow process, there are a variety of factors and they are coupled interaction. Based on the above-mentioned basic formation mechanism of debris flow on many factors, this paper carries debris flow analysis, combined with previous research results were extracted and debris flow-related one hour maximum rainfall,the amount of time alluvial largest party, the average thickness of loose material, drainage area, main channel length, watershed relative elevation, hillside average slope, vegetation coverage, 24 hours maximum rainfall, basin population density 10 variables. Then it calculates with factor analysis and extractes water conditions, topography, provenance condition, human activities, prevent mudslides outbreak six main factors namely six evaluation. So it uses these six indicators to establishes evaluation Index System for mudslide outbreaks of Ya'an City.(3) According to the above-mentioned six main factors, this paper uses factor analysis to establish the weight of each main factor, and calculate the total score for each factor. Then, this paper uses cluster analysis to make their risk rating. So this paper establishes the debris flow hazard assessment model based on factor-clustering analysis.(4) According to debris flow hazard assessment model established above, this paper makes debris flow ditch hazard assessment of Ya'an city. The results show that in the regionthere are 15 debris flow ditch in low risk, 19 debris flow ditches in moderate risk, 10 debris flow ditches in high risk, 1 debris flow ditch in extremely dangerous risk, consistent with the actual situation.