Multi-scale Natural Disaster Scenarios' Risk Assessment And Zoning

Learning from several disasters in history, human being recognized risk management, prevention and control is the lowest cost and most convenient way of disaster response. It is also recognized that strengthening disaster risk research and improving risk management & early warning capacity has a very important significance for reduction of life and property, improvement of decision-making capacity for all levels of government and mitigation of disaster's adverse factors. The significance of multi-level administrative divisions is to integrate regional disaster prevention and mitigation resources more effectively, build disaster risk management technology system and promote the formation of risk reduction cultural system.The government, enterprises, communities and individuals were coordinated organically for common response to disaster risk.The thesis was supported by the National Natural Science Foundation of China (NSFC) "Scenario Analysis of Emergency Responses to Natural Disasters Risk in Coastal Cities" (No.40730526), "Study on Natural Disasters Risk Assessment System in Chinese Coastal Cities" (No.40730526) and PhD Program Scholarship Foundation of ECNU (No.2010035). The theory, method and empirical researches of disaster risk assessment had been studied at different spatial scales. On the basis of collecting and collating of literature, several typical typhoon disaster scenario investigations and disaster loss researches had been organized. For typhoons rainstorm-flood disaster system, disaster risk assessment of three levels of scale was carried out, which were large scale-Wenzhou City, meso-scale-Pingyang County and small-scale Shuitou Town. Multi-scale natural disaster risk expression paradigm and methodology were constructied. Typhoons rainstorm-flood disaster risk zoning map in multi-level administrative regions of Wenzhou City has been compilatied. Several key measures to deal with disaster risk in different areas have been proposed for regional disaster risk reduction planning and sustainable development construction.The main results of the paper are as follows:(1) Systematically, this paper discusses the composition and inherent relationship of disaster risk factors. Characterization of disaster risk factors include: spatial extent, the future time span, strength of disaster loss and disaster probability. Among them, the space of risk scenarios includes large scale, mesoscale and small scale. Future time span and the probability are the time scenarios of risk. Loss of strength is the disaster scenario of risk. The value of disaster risk is only characterized in a particular combination of scenario conditions. It is not meaningful for regional risk management without disaster scenario definition. The general idea of natural disaster risk scenario analysis includes hazard analysis, vulnerability analysis, analysis of disaster losses and disaster risk classification and zoning.(2) Systematically, this paper disacusses the spatial scale problem of disaster risk studies. Disaster risk has both natural and social attributes. There are significant and meaningful spatial scales for risk factors. There is a significant difference of disaster risk characterization at different spatial scales, which depends on the location of disaster discipline in the scientific system of man-land relationship. Spatial scales of disaster risk includ three types:large-scale, meso-scale and small-scale. The large scales can be divided into the global level, continental level, national level, provincial and municipal level. The meso-scale level mainly refers to the county and district level. The small scale includs the township level, street level, community level and so on. In this study, large, medium and small-scale typhoons rainstorm-flood disaster risk assessment was carried out in sub-national regions.(3) This paper completes an empirical study of disaster risk assessment in sub-national large spatial scale region. Taken Wenzhou City, Zhejiang Province as the empirical area of municipal large-scale, typhoon rainstorm-flood risk factors include hazard, vulnerability and disaster loss. Comprehensive disaster risk lebel depends on matrix combination of disaster enormous losses and the potential probability. The average rainfall of 100 year typhoon storm is 500mm. The depth of flood inundation is 0.5m. The disaster loss rate is mainly 50%. The average maximum loss is 2 million yuan/km2. Large-scale disaster risk assessment grasps the principle of "good order of magnitude, reasonable distribution and equivalent division ". The evaluation results are used to identify regional disaster risk characteristics, guiding the planning and implementation of disaster prevention preparation and mitigation.(4) This paper completes an empirical study of disaster risk assessment in sub-national medium spatial scale region. Taken Pingyang County, Wenzhou City as the empirical area of district level in medium scale, typhoon rainstorm-flood risk factors include hazard, vulnerability and disaster loss. Comprehensive disaster risk lebel depends on the function of disaster enormous losses and the potential probability. The average rainfall of 100 year typhoon storm is 520mm. The average depth of flood inundation is 4.0m. Loss rate of agricultural land and commercial land in the disaster is between 90% and 100%, and forest land loss rate is of 70%-80%. The average maximum loss concentrated in 1-3 million yuan/km2. Medium scale disaster risk assessment grasps the principle of "regional differences, probability factors, not equivalent division". The evaluation results are for the construction of regional flood control project and facilities layout.(5) This paper completes an empirical study of disaster risk assessment in sub-national small spatial scale region. Taken Shuitou Town, Pingyang County as the empirical area of township-level in small-scale, typhoon rainstorm-flood risk factors include hazard, vulnerability and disaster loss. Comprehensive disaster risk lebel depends on the strength characteristics of the principal component factors. The average loss rate in housing property is 20% and business assets reaches 30%. The average maximum loss concentrated 40 000-100 000 yuan of room. Small-scale disaster risk assessment grasps the principle of "regional characteristics, case accumulation, long-term record". The evaluation results are for reference of the regional temporary migration program design and implementation.(6) This paper establishes a plan system of regional disaster risk response for sub-national multi-seal regions. The effect of different spatial scales'regional disaster risk reflected in the data accuracy, risk characterization, risk classification, risk maps and so on.The scale coupling of disaster risk includs two aspects scaling down and up. The response of large-scale region to disaster risk is to establish early warning mechanism, with that to strengthen the construction of flood control projects for the medium-scale region and to carry out temporary migration for the small-scale region respectively. Improving the risk map atlas and disaster emergency preparedness system of multi-level administrative unit are the most effective and direct means to enhance the ability of disaster prevention and increase awareness of risk prevention.The main features and innovations are as follows:(1) Based on the results of previous studies, disaster, risk, scenarios, scale and other related concepts were defined and analysised theoretical. The paper proposed combination of disaster risk scenario conditions and focused on disaster risk scenario types, scenario risk expression and and risk scales effrcts in different spatial scales.(2) Based on a large number of investigations and the processing of computer analysis, the paper completed typhoon storm-flood disaster scenario risk analysis and evaluation of three level spatial scales in sub-national region. For southeast coastal mountain cities in China, Zhejiang province, Wenzhou city, Pingyang county, and Shuitou town three spatial scales, the potential maximum loss was estimated and the distribution high-risk areas was determined under different flood return period.(3) Based on the results of multi scales hazard risk assessment, different targeted programs coping with disaster risks was proposed. Large-scale area is "Rainstorm disaster risk warning signal and response guide in Wenzhou city. Meso-scale area is "Design of stabilization and risk reduction program for typhoons rainstorm-flood disaster in Pingyang county". Small scale area is "Temporary migration program for 50-year rainstorm-flood disaster in Shuitou town".