Debris Flow Risk Assessment Of Bailong Basin Based On Information Entropy And AHP Model

Bailong basin was one of the serious areas of debris flow in china, and having the characteristic of great frequency and hereditability. The structure of mountains, rock and soil are severely damaged under Wenchuan "5·12" earthquake influence, induced a serious of geological disasters included Zhouqu "8·8" Catastrophic debris flow. The serious geological disasters threatern the the life and property of the people, significant infrastructure and even to the Ecological Security in the Upper Reaches of the Yangzi River, controlling techniques and Risk assessment of debris flow in the Bailong basin were of important realistic significance.Based on the analysis of the environmental factors of the internal and external force, establishing the symbol system, the Information Entropy and AHP model were applied to assess the risk of debris flow in study area and have a Comparative Analysis of the result of assess model. The results showed:1. based on Geodatabas, built the space database of debris flow and its relating factors which included the underlying database, spatial database of geological environment and debris flow to develop a base for risk assessment of ebris flow in accordance with the practical investigation in the field and Related documents.2. The results showed that the spatial distribution characteristics of debris flow of the great density distribution, conspicuous spatial heterogeneity, the notable disparity of altitude distribution of debris flow in different areas of the same catchment, debris distributed along the Fault zone and the areas of the soft and weak rock mostly.3. The distribution feature of debris flow time mainly includeed the annual time distribution, years time distribution rule and day time distribution rule. The distribution for the annual time performanced that debris flow occurs in a wet year and tended to be in a wet year, and not yet developed in low rainfall and tended to be low rainfall of the year; The distribution rule for the years time of debris flow performance that the time debris occurred mainly distributed in June to September, and concentrated in July-August. The distribution rule for day time performance for the debris flow occurs in the afternoon (14to20) and the night (24to8at the next day). 4. According to the development background, the forming condition, the distribution and other factors of debris flow, do factor analysis, collinearity diagnostics and correlation calculation with every factor, established the assessment indicator for debris flow hazard degree separately based on grid unit and valley unit. And the impact factors of debris flow hazard degree based on valley unit are listed in turn here:formation lithology> main ditch length>10minutes average rainfall> valley relative relief> valley area> NDVI> main ditch gradient> valley cutting density.5. In the paper, it firstly adopted AHP model to conduct the risk assessment of debris flow, but due to the limitation of the AHP method, the evaluation result has the very strong subjectivity. In order to overcome subjective factors to affect the results of evaluation of debris flow in the largest extent, and based on grid unit and watershed unit to conduct the risk assessment of debris flow using the information entropy model, which respectively produced based on grid unit and space distribution of debris flow risk assessment in Bailong Basin. The result showed that the debris risk assessment outcomes by the two methods are alike, with difference only in local regions, however, the one based on basin unit is accordant with the actual situation, indicating that hydrologic terrain condition has a strong role the occurrence of debris flow, and more hydrological terrain index must be adopted in debris flow risk assessment, in order to make the assessment more exact and reasonable.6. Based on grid unit’s information entropy model and the AHP model of debris flow risk assessment, the two results presented a general trend similar, and the characteristics of the local slightly differences. A comparative analysis of the two kinds of evaluation results showed:a fault in the study area of space debris flow risk distribution plays a leading role.