Quantitative Risk Assessment In Debris-Flow Disaster

Globally, China is one of the countries mostly affected by serious natural disasters of variety, widespread and great harm Debris flow disaster is one form of these geological disasters. The geological disaster risk evaluation method can comprehensively evaluate the relationship between the geological disaster and mankind. Debris flow risk quantitative assessment is a combination of geographic information technology and mathematics methods of probability and statistics which provides a more accurate calculation for debris flow disaster risk evaluation as well as a scientific basis for prevention and control strategy of disaster.Basing on remote sensing data, debris survey data, social and economic data, Sichuan province was taken as study area in this paper. Disaster susceptibility, hazard vulnerability and risk of debris flow in Sichuan province were zoned and evaluated utilizing approaches including analytic hierarchy process(AHP), method of extenics, Xi-lin Liu model, ArcGIS software. Main study results are shown as follows:(1)In the extenics method, the relationship between the risk rating and evaluation index was analyzed after quantifying the impact factors. In order to make the correlation function conform to the actual environment, three kinds of correlation function A, B and C were used to indicate the magnitude of the quantity value along with the trend of the debris flow risk grade in the same or opposite directions respectively. Slope and relative height difference were combination of A and B. Rock hardness and vegetation coverage are combination of B and C. Rainfall, gully density, historical debris flow inventory, historical earthquake inventory are C.(2)The debris flow risk results were calculated by raster calculator of Arc GIS with the process of grid statistics analysis. The results shown that the I, II, III grade dangerous degree accounted for 84% of the area of Sichuan province, indicating that in most areas of Sichuan province were safer. Verification points into the medium, high, heavy danger area accounted for 76% So that introducing extenics method into large scale debris flow risk assessment was feasible.(3) Vulnerability calculation of debris flow was processed with Xi-lin Liu mode, which is a fitting experimental formula. Factors will be generally divided into two categories in Xi-lin liu mode, monetary measuring factors and nonmonetary measuring factors. In this paper monetary measuring factors included substance vulnerability, economic vulnerability and environmental vulnerability. Non-monetary Social vulnerability was regarded as the nonmonetary measuring factor.(4) Debris flow disaster risk was calculate as the product of the disaster risk and the vulnerability of debris flow. According to the calculation results of debris flow disaster risk and vulnerability, risk of debris flow was leveled by utilizing natural segment method which was commonly used in statistics.