The Risk Assessment Research Of Debris Flow Disaster In Longzi Town Of Tibet

Debris flow disaster is one of the common geological disasters in mountain area,it has group-occurring,simultaneity,suddenly and huge disaster forming such characteristics,seriously affected the development of economic development in the mountain area.with the deeply exploitation of the west area,our country increasing gradually the prevention kynamics about the geological disasters in mountain area,the risk assessment of the debris flow also gradually induced the attention of the experts and scholars.By many years of research,the risk assessment of debris flow have achieved a certain progress on theoretical and practical aspects. but , because of the complicated formation of debris flow, the risk assessment evaluation has not formed systematic and consummate theory, and there is no unified evaluation standard, different department or different scholars often have different evaluation result about one disaster, the research on quantitative evaluation is especially weak.so,provide a method which has strong application and reliable results have important significance.This article relied on china geological survey"the investigation and hazard mitigation measures of the himalayas'serious geological disasters",depend on debris flow disasters in Longzi town of Tibet,carry on research about risk assessment of mountain debris flow,hope to by means of theory to guide application,and provide technical support to prevention of the mountain's debris flow.This article first introduces the natural geology of Longzi town of Tibet, from the meteorology and hydrology,topography and geomorphology,formation lithology and hydrogeology condition, comprehensive and systematic analysis the sub-formation conditions,growth characteristics and distribution character of the Longzi town's debris flow.show that the town of Longzi has adequate conditions of the debris flow: (1) weathered broken rock strata is conducive to the formation of loose solids. (2) the huge relative height difference, huge hillside slopes, provides a good condition for the outbreak of debris flow. (3) weather conditions in this area is conducive to the formation of debris flow. the rainfall characteristics of Longzi manifested as low-intensity, long-lasting. Type of rain areas in the storm area, and precipitation stable, relatively uniform intensity. When by the low-intensity rainfall makes saturated rock and soil, it is likely to arouse critical state of rock and soil, resulting in the formation and development of debris flow.Secondly, this article introduces the choice of theory of methods of debris flow risk assessment,the evaluation index system for the establishment of the principle of screening methods, and detailed methods of data processing steps, in this paper, we taken based on the "disaster entropy - a comprehensive evaluation of extension" approach to carried out the risk assessment on debris flow of Longzi.The third,take the example of three typical debris flow, discuss the development features,gully feature as well as analysis of the causes. On this basis and then to carry out the risk assessment index system research of debris flow , through access to information at home and abroad, as well as the trench site investigation data analysis of 11 debris flow field, selected out the maximum amount of debris flow, the main channel slope, degree of weathering of rocks, vegetation cover, slope gradient of the formation of the district, years of average rainfall, loose material reserves, the relative elevation terrain, erosion and deposition variation, population density, drainage area as the "risk factor", then use the "correlation" method of fuzzy mathematics, optimal screening to the 11 factor ,and ultimately determine the maximum out of the volume of a debris flow, drainage area, erosion and deposition variation, relative terrain elevation, average rainfall years, the loose material reserves, the population density, degree of weathering of rocks as the "evaluation factor" of debris flow risk assessmentFinally, use the "disaster entropy - a comprehensive evaluation of extension" theory, determine the weight and the risk assessment of the evaluation factors, as well as the danger of debris flow ditch grading, carry on risk assessment to the 11 debris flow of Longzi, access their evaluation results, and compared with the actual situation, in line with the actual situation of the study area to illustrate the use of "disaster entropy - a comprehensive evaluation of extension" methods of risk assessment of debris flow is feasible.In this paper, the main research results obtained are as follows:1. Longzi have longitudinal valley, and huge relative height difference, complex and diverse regional geological environment, rainfall is not large but more concentrated, resulting in frequent development of debris flow disasters.2. This article the regional geological environment, the distribution of debris flow disasters, characteristics and influence factors and formation mechanism are analyzed, and on the basis of a large number of documents available the combination of previous work experience and accumulation of the applicability of both the region the use of " correlation " theory and the selection of the debris flow hazard assessment index system, in order to truly reflect the actual situation of debris flow disasters, in order to lay the foundation for disaster prevention and mitigation. Evaluation in the specific application of the study area, indicating that the selection of indicators to evaluate more reasonable.3. The impact of debris flow risk of a number of factors, a variety of factors on the extent of the danger of debris flow disaster the size of the contribution varies. In this paper, "Disaster entropy" theory, to draw the debris flow risk assessment factor, the weight value, more objective, quantitative evaluation of the response of the various indicators of the extent of the danger of debris flow disaster the size of the contribution.4.The "disaster entropy - extension comprehensive evaluation" approach, the risk of debris flow disaster to carry out a comprehensive evaluation study is the evaluation of debris flow hazard in a useful attempt to evaluate the results of the real objective, have high practical value.