The Research And Improvement Of Risk Analysis And Evaluation Method On Flood Disaster

Floods is a kind of natural disasters which has serious influence and danger to the human beings. Since the20th century, natural variation mainly appears in global-warming-based climate change, urbanization was apparently most pronounced among people's social life and economic activities. Such appearances have a huge impact on natural disaster especially on flood disasters. Although mankind has entered the age of information, science and technology have been developed rapidly, the construction of flood control system has been improved, but flood disaster still happen from time to time, or even it get worse. Human beings must be able to really realize the sustainable socioeconomic development and the consonance between human being and water. How to face the risk of flooding along with global climate changes, which is an issue counting to sustainable economic development and harmonious society in our country, is also an urgent problem to research and solve.In recent years, the human has put forward the new flood control and disaster alleviation strategy from historical experience of the competition between economic development and the flood disaster, which is to manage the flood disaster, to adjust the relationship between human and water, to transform the original" flood defence" to "flood management", and to realize the harmonious development of man and water. And in the flood management, flood risk management is one important work. It's a complex system engineering involving the analysis, evaluation, prevention and treatment of the flood. With the weather and climate change, extreme events occurring frequently and their intensity being aggravated constantly., people demand for higher performance of the flood management, Carrying out the research of flood risk assessment and division can not only make up for the deficiency of the flood risk research in our country, it can also enrich and develop our flood risk management theory basis and method system.This paper is supported by plan "973"—the National Basic Research Program of China (Project No.2007CB714107)" Dam break mechanism and risk control theory under complicated conditions" and by state technology supporting plan "Flood control technology research in the middle and lower reaches of Yangzi River after the use of the Three Gorges Project (2006BAB05B05)", based on first-hand data through conducting site visits and research, we set up the theory and methodology of flood risk assessment; set up risk assessment system in the situation of small example scale; researches has very important scientific value and realistic meaning on building better security protection system to achieve flood and disaster relief as well as harmonious development of man and nature.Risk analysis is based on the traditional mathematics probability theory, calculation method is statistical method. This paper puts forward the objection and consider that the mathematic basic of the risk analysis is fuzzy set theory because that input output relationship can only be expressed as fuzzy relations owing to the natural disaster complexity. There have been some mature methods on the research of every part of natural disasters. The main task of natural disaster risk analysis is how to connect them organically and put forward the improving suggestions on the results of the research.This research is based on the system theory, using the fuzzy mathematics theory as the basic tools, and it introduces the fuzzy mathematics method of information diffusion method into flood risk analysis field. Natural science, social science for reference, environmental science and scientific system and many other branches of the related theory method are widely used. Aiming at the risk evaluation in the flood control and disaster alleviation, in this paper a thoroughly and systematical study is made center on theory, model, method and application. And we strive to get more stable and actual risk of results. This paper includes the following aspects:1. This paper introduced academic monographs on the theory, method and application of flood risk evaluation and risk evaluation. This paper absorbs the domestic and foreign advanced research result, by means of quantitative research, analysis technology and method as the means such as principle companent analysis, fuzzy mathematics,, AHP method, BP model and information diffusion. After further investigating the the flood disasters and disaster risk formation mechanism, we construct the risk assessment theory frame, index system, method and the model, and we calculate the risk grades and draw the corresponding risk figure by means of GIS. 2. It discusses the basic theories of the natural disasters risk evaluation, and emphasize the risk essence, the basic principle of natural disaster risk analysis, probability and statistics method and fuzzy systematic method in risk assessment, and it improves the principal component analysis method. According to the flood loss data of10area in1998, and the loss of the10area were compared and ranked, in order to compare the severity of the flood disaster in different provinces, The result showa that the assessment has stronger comprehensiveness and can reflect the evaluated problem fully and truly. This paper provide the general procedure and calculation method of systematic analysis and decision, and it can be seen from the model calculation conditions that it is universally applicable for sorting and assessment problems.3. This paper Introduces theory and model on flood risk evaluation under the condition of incomplete information, detailed the application of the proposed model and flood risk evaluation theory under the condition of incomplete information including information matrix framework, information distribution method, information diffusion principle and normal information diffusion, and further more put forward put forward the improved information diffusion method. Based on this method, combining with China's national conditions and historical material, it establishes the flood risk comprehensive evaluation model and method, synthetically considering the complexity and variety of the social, economic and environmental system. Proper information inflation can improve the precision of risk assessment so as to supply scientific evidence for flood control planning and decision and enrich the flood risk assessment theory system. This paper also uses improved information diffusion method and variable fuzzy set model, and make empirical research on the evaluation and analysis of flood risk degree and return period with the measured data from1949to2009.4. This paper uses the computer simulation technology in the reliability demonstration of the model. By using the computer simulation, both the advantages and disadvantage of several methods are compared, a suitable and efficient numerical calculation method is proposed, and also the validity and practicability of the improved risk assessment method are illustrated.5. Based on GIS technology and information diffusion method, a compiling method of flood risk zoning map are introduced in this paper. The flood risk zoning map illustrates the distribution of disaster risks and the changing spatial trends with the increasing risk degree. AS a part of the research results of the plan "973"—the National Basic Research Program of China (Project No.2007CB714107)" Dam break mechanism and risk control theory under complicated conditions", the relevant research results have been completed and passed the check. The flood risk zoning map completed by our project team is highly descriptive and matches well with the actual situation. Theory and real data tests demonstrate that the information diffusion method presented is satisfactory under the condition of small sample.Flood risk assessment is an interdisciplinary research which include hydrological water dynamics, meteorology, environmental sciences, environmental sciences, geography, risk discipline and catastrophology. Although this work has offered a useful exploration in flood risk assessment and risk zoning, it is just at the beginning of the solution of the problem and the scientific development of the theory. Flood risk assessment is a complicated system engineering, and the further detailed research is still needed in both theory and practice.