Quantitative Methodology And Application Of Urban Natural Disaster Assessment

Looking back into human development history,it is easy to find that this is not only a history to fight the nature,but also a history to conquer ourselves for mankind. From some ancient myths as "Nvwa mended the sky" to legends as "Dayu controlled water",from the victory of conquering "SARS" to the battle of resisting "bird flu", the fight between mankind and disasters never ends.As the urbanization degree continues to be improved,human civilization is advancing increasingly.But a great amount of facts also prove that there is a interaction between urban development and disasters nowadays,namely,various faults in the urbanization course aggravate the situation of urban disasters,in turn,the worse situation hinders the sustainable development of a city.So human beings face new trials.Currently,disaster management has become an important means to realize the urban sustainable development all over the world,while disaster assessment is always one of the important steps and the basis of all decision makings of disaster management.Disaster assessment is a basic foundation for reflecting disaster situation in all respects, confirming goals of disaster reduction,optimizing measures to disaster prevention, resistance and rescue,evaluating benefits of disaster reduction and making decisions of disaster reduction,as well as important references for making land exploitation and utilization plan and social and economic development plan.In terms of systems theory, urban disaster assessment target has such characteristics as high dimensional system structure,complex correlation and nonlinear action.As a result,it is an arduous task and has great effects to conduct urban disaster quantitative assessment.The contents of disaster assessment,however,are so extensive that it is impossible to explore all the problems in the transitory term of doctoral education.Therefore,this paper mainly focuses on some current hot or difficult spots of disaster assessment taking earthquake and storm surge as examples.The main contents and innovations are as follows:(1) Firstly,based on large amounts of literature review,the interaction between the urban development and appearance of disaster is demonstrated.Secondly,the effect of disaster assessment in urban disaster management and sustainable development is elucidated.Thirdly,the development history of disaster assessment, especially the quantitative assessment conducted at home and abroad,is reviewed. Fourthly,the four dimension mode of the disaster assessment is proposed, combination of which constitutes the disaster assessment space.In the end,methods of quantitative assessment and their applications in natural disaster assessment are summarized,which are methodology basis on which researches of disaster grade assessment and capacity assessment on disaster prevention and reduction are conducted. (2) A fuzzy cluster analysis model of urban natural disaster grade identification is constructed.At first,concepts of disaster grade and disaster grade assessment are clarified.Then,contents of disaster assessment are elaborated,which include denotation methods of disaster grade,index system and computation methods of disaster grade assessment,and gradation method of disaster grade,and some imperfections are pointed out.On the basis of the above research,taking storm surge disaster for example,using data of direct economic losses,death number and disaster area,pattern classes of disaster grade are created by fuzzy cluster method.Then the samples needing to be assessed are identified by fuzzy measure of similarity.So the methodology system of disaster grade assessment is established with such a step that grade identification follows the fuzzy cluster.Compared with other methods,this methodology system suits the human cognition process better.In the end,applicability of this method is discussed,and the fact that applicability range and reliability of this method is decided by amount and regional character of samples is pointed out.(3) A grey neural networks prediction model of urban natural disaster grade is proposed.Compared with assessment after disaster,obtaining disaster grade information prior to disaster or during disaster term will help people implement disaster rescue,personal and relief materials assignment and reduce losses better and in time.Taking storm surge hazard data as training sample,a three layer BP neural networks model with a goal of disaster grade is established,and a hindcast is conducted using this model.Natural hazards are selected by grey correlation method, and in this way,amount of prediction work is reduced and prediction precision is improved.Case study testifies the feasibility of this method.(4) A fuzzy synthetic evaluation model of seismic resistance capacity of urban communities(FSEMSRCUC) is presented.Assessment method of disaster prevention and reduction of urban communities is discussed using seismic disaster as example. Differing from assessment of seismic resistance capacity of constructions,impacts on seismic resistance capacity caused by multiple factors are fully considered in FSEMSRCUC,these factors consist of building density,population density and damage degree of buildings under certain seismic intensity.Weight of each index is confirmed by sorting method,and fuzzy synthetic evaluation is used to overcome difficulties of gradation of seismic resistance capacity caused by grade concept fuzziness.Using spatial data management,analysis and mapping ability of ArcGIS, fast evaluation system is built with a model base embedded with the fuzzy synthetic model.This system realizes informatization and visualization of decision making and thus greatly enhances its effectiveness.Through evaluation on seismic resistance of communities,its spatial distribution characters are confirmed,which can point out the focus of urban routine work of disaster prevention and reduction and provide scientific basis for urban reconstruction especially for decision making of seismic resistance planning.(5) A three level fuzzy synthetic evaluation model of urban capacity of seismic prevention and disaster reduction is established.The key steps include index system construction of capacity of urban seismic prevention and disaster reduction, confirmation of index weight and selection of evaluation method.In this study, framework of index system is primarily constructed by literature review and expert meeting,and then the selected indexes are filtrated through two rounds of letter inquiry by modified Delphi method,in which some statistics such as average value, coefficient of variation and authority coefficient are adopted as control measures. Targeting the stronger hierarchy character of index system,weight of each index is obtained by the classic AHP method.Because the index system includes so complex and numerous indexes that the evaluation standard is not unified at present,so multiple level fuzzy synthetic evaluation method is adopted to overcome such difficulties that data are not sufficient and qualitative indexes are too much by fully using expert experience at current research stage.