The Typical Debris Flow Ditch Based On The Theory Of Extension Risk Assessment In Yunnan Province

Yunnan province is one of the provinces that frequently hit by debris flow in china due to its special geographical environment.The occurrence of frequent debris flow not only causes huge losses for people's lives and possessions,but also affects the development of Yunnan's economy.Therefore,the study of the risk caused by debris flow ditch can prevent and decrease the occurrence of debris flow,and at the same time,boost the economic development in Yunnan.This thesis chose the geographical environment in Yunnan as objective and found out that the geographical condition,hydro-logical condition and human activities were the formative factors of debris flow.Moreover,the author also calculated the statistics of the occurrence frequency,the death toll and economic loss caused by debris flow.To avoid the influence of subjective factors,the author first used the entropy method to get the proportions of each assessment element and then used the extension method to build an risk assessment model of the debris flow ditch.The study found out that the assessment elements,proportion well reflected the importance of each element and the risk of debris flow and the reality fit better in the extension method model,which will be beneficial to the study of debris flow.This thesis was divided into six parts.The first part mainly stated the background and value of this study,as well as its present state and the process of conceptualization.The second part illustrated the basic situation of debris flow disaster from the perspectives of geographical situation,the formative factors,the spatial and temporal distribution and the danger of debris flow in Yunnan.The third part expounded relevant theories in this dissertation,including the entropy method and the extension risk assessment.The fourth part was the empirical analysis of this study.The author chose several debris flow ditches,using the entropy method to confirm the weight of assessment factors and using extension method model to get the assessment results.The fifth part were the coping strategies which aimed at preventing disasters and reducing damages in Yunnan.The sixth part were the conclusion and the outlook of this study.The author reviewed all the works done in the previous chapters,drew a conclusion and made discussions and outlook for the risk assessment of debris flow in Yunnan.