Study On The Method Of Geological Disaster Risk Assessment Based On GIS

Geological disasters, including landslides, collapses, debris flows and so on, are related to geological processes, which are induced by natural factors or artificial activities and are harmful to people's lives and property safety. China is one of the countries whose natural disasters occur largely and its loss is the most serious in the world, with many kinds of disasters, wide geographical distribution and great loss. It cannot be evaded to cope with natural disasters, which is one of the issues needed to be solved for human survival and sustainable development. Living with risks and always being prepared to take preventive measures are a basic point and starting point for disaster mitigation and disaster management.In this paper, to the unexpected natural disaster emergency response, study on the rapid disaster risk assessment method with multi-source data based on GIS, is the major requirements of geological disaster risk management suggested by China's government departments, which would serve to government and local community to solve the major technical problems existing in the loss of geological disasters emergency evaluation, and provide information-assurance and decision-making support for all kinds of unexpected natural disaster response, mitigation, etc. The following major elements:(1) The definition and connotation of geological disasters were described. The theoretical system of geological disaster risk assessment was discussed. Based on the analysis and summarizations of researches home and aboard, the dissertation tries to analyze the development status,trends and shortages of geological disaster risk assessment research.Systematic summary of the geological disaster analysis and risk assessment methods based on GIS were executed, including the model technology of hazard assessment, vulnerability assessment and risk assessment. Geological disaster risk assessment index system and evaluation flow were built.It laid the theoretical foundation for the geological disaster risk assessment studies.(2) Geological disaster risk rapid assessment system was built based on C# program and development platform of ArcGIS Engine.The system was mainly served for government departments to facing the unexpected natural disaster emergency response,and with the technology of using multi-source data to assessed risk of geological disaster.The major functions of this system are:①Realize the common basic function of spatial analysis, extraction of terrain property, such as slope, aspect, curvature, raster calculator, vector and raster conversion, and clip with mask, and so on.②Realize the function of spatial analysis, spatial statistic and Visual Expression.③Automatically partition slope factor, slope direction factor, curvature factor, relative relief and geomorphologic information.④Realize the function of extracting drainage density, fracture density, disaster points density and automatically partition.⑤Function of geological disaster risk assessment based on information value methodology and expert knowledge.⑥Function of automatically input and visually output mapping, such as*.bmp,*.tif,*.jepg, and so on.(3) A case study in "4.14" Yushu earthquake, this dissertation is detailed analysis of environmental geological conditions, spatial distribution characteristics of earthquake-induced secondary geological disasters, pre-disaster and post-disaster monitoring of geological disasters. Earthquake-induced secondary geological disaster risk assessment index system was built and extraction and quantitative methods of evaluating indexes based on GIS technology were discussed. Technological flow of earthquake-induced secondary geological disaster hazard assessment, vulnerability analysis and risk assessment and mapping based on sensitivity coefficient, expert knowledge and GIS technology were finished. Risk assessment map was categorized into five classes, that is, "very low", "low", "moderate", "high" and "very high" Some suggestions and strategies were given and would provide decision-making support for emergency relief and post-earthquake reconstruction in the area.(4) The result of risk assessment of geological disaster induced by Yushu earthquake indicated:①Earthquake intensified hazards of the secondary geological disasters in local areas, although its damage is limited. Landslides, collapses, debris flows disasters mostly occurred on both sides of earthquake rupture zone and its surrounding. Fully avoiding and safety measures should be taken to resolve the insecurity problem.②In socio-economic developed areas,the risk of disasters will be the greatest. This is because the population and the cities are crowded, the industry activity is frequent, and there are many hazard bearing bodies with high density and value.Although their bearing capacity of regional disaster is relatively strong and the loss is relatively low, the absolute loss and its density is actually high. It warns us to understand vulnerable regions of the traditional and the vulnerability of developing nature,society and economy. It is necessary to improve disaster risk management system under the new situation so that disaster risk could be reduced.