Research On Hazard Assessment Of Debris Flows In Min County Gansu Province

Recently, with the development of the economy of mountain area in China, the rapid increase of population in Min county Gansu province, river gulley level land cann't satisfy people to the grain need and it results in more and more steep slope field to be reclaimed year by year. Meanwhile, the mountain vegetation deterioration , water and soil loss will lead to the more occurrence of the mud-rock flow geology disaster, threatening safety of the local people's lives and property directly. Therefore, the mud-rock flow disaster mechanism research, hazard assessment, scientific prevention measures of the debris flows must be strengthened. This paper, according to physical geography environment of Min county, field investigation, combining with preliminary records and document data of debris flow disaster in the past, analyzed characteristics and contributing factors of 148 debris flows in Min county. Combining formation mechanism of debris flows hazard with fuzzy mathematics and catastrophe theory, this paper completed hazard assessment of 90 single debris flows and 6 valley units of debris flow in Min county Gansu Province and proposed reasonable prevention measures and countermeasures using respectively fuzzy comprehensive evaluation method and Catastrophe Progression Method. The results are found to be coincident with practical situation. It is a important significance and reference value for economic construction, defending and reducing disaster practice of Min county. Meanwhile, the method of evaluation combining catastrophe theory with fuzzy mathematics theory proved a new way in solving multiple rule-decision regional dangerons evaluation of debris flows.This thesis is devided into seven parts.The first part is the preface, briefly introduced the research background, significance, progress of debris flows'home and abroad, as well as the theoretical foundations and methods used in this study, determined the overall research idea .The second part determined the study area, illustrated briefly characteristics of meteorology, hydrology, soil vegetation, topography, geological structure, earthquake, as well as supply, runoff and drainge of the groundwater. At last, proposed the current disaster situation and facing problems of debris flows.The third part, according to the previous analysis and research to the characteristic of the debris flows disaster, three basic factors such as rich solid material resource, essential terrain and enough hydrodynamic, analyzed characterrisitics of disitribution and development of the debris flows disaster. According to the diversity, variability, complexity of the geological environment and conditions in Min County, debris flow gully formed a more complicated disaster"fuzzy"system from the formation, development to the disappearance by a lot of factors influence. The fouth part introduced fuzzy mathematics theory into the dangerons evaluation study of the debris flows. This paper which used fuzzy comprehensive evaluation method and referenced domestic relevant literature of Liu Xilin, Gongxue, Chen Wei, finally selected eight dangerons factors such as valley relative elevation,degree of vegetation cover and so on. It completed single gully risk assessment about the 90 debris flows in the Taohe valley of Min county and analyzed inherent and external causes of formation to the debris flows disaster based on natural and human ecnomical activities, assumed forecast analysis of the develeping trend of Min county debris flow disaster in future.The fifth part , based on analysing the mechanism of the mud-rock flow disaster , generally expounds the principle and characteristic of the catastrophe theory. Then, combining the mechanism of the mud-rock flow disaster with the catastrophe theory, it gave the regional dangerons evaluation of the six river basin with the Catastrophe Progression Method. The evaluation result is that: the areas belonging to high danger are the main stream river of the Taohe river basin (Town- Weixin), (Town-Xizhai), the middle and upper reaches of the Nanahe river basin (region of Hetuo) . The areas belonging to middle danger are Shili-Qinxu-Sigou-Mazichuan southern moutainous district, Puma-Shendu-lvjing eastern moutanious district. The area belonging to low danger is Mawu-Suolong eastern moutanious district. Eventally, it sumed up the merit and the scientific of the zonation of the debris-flow hazards in Min country with the Catastrophe Progression Method, and made the map of the comprehensive zonation of the debris-flow hazards according to the results of the evaluation.Part VI integrated the parts of the previous research results, highlighted the"people-oriented"principle , proposed systematicly prevention measures and countermeasures of the debris flows disaster in Min county, established monitoring networks and early warning system of mass monitoring and preventing of the debris flows disaster. Meanwhile, it provided the necessary basis and reference according to the plan for the local government to carry out the debris flow disaster prevention, to reduce disaster loss and to protect people's lives and property.The seventh part is the paper's summarization and main conclusions.