Assessment On Comprehensive Vulnerability Of Storm Surge Disasters Of China's Coastal Regions

China is one of few countries in the world that is influenced by tropical storm surge and extratropical storm surge at the same time. Storm surge disasters could occur throughout the year, from north to south with serious loss. Especially under the context of global warming, the frequency and intensity of tropical cyclones and storm surges will increase, which leads to increasing risks of disasters further in coastal areas. It is agreed that vulnerability studies is the field that human beings could accomplish something to disaster prevention and mitigation, to reduce the impacts of natural disasters. Supported by the Foundation of National Natural Science of China "Scenario Analysis of Emergency Responses to Natural Disasters Risk in Coastal Cities" and "the Shanghai Youth Science and Technology Venus Program", a large number of documents and data collected, and based on the progress of storm surge disaster vulnerability research home and abroad, physical vulnerability, social vulnerability and comprehensive vulnerability of storm surge disasters are analyzed and assessed on a large scale in the coastal regions of China. It's spatial differentiation and dominant factors are identified, which provides a scientific basis for developing countermeasures to reduce the vulnerability of storm surge disasters for different regions. The research findings are as follows:(1) The storm surge disaster vulnerability index (Storm Surge Vulnerability Index, SSVI) is built by learning form the assessment method of Coastal Vulnerability Index (Coastal Vulnerability Index, CVT). According to the storm surge disaster loss data from1990to2009of eleven provinces in the coastal region, physical vulnerability of storm surge is assessed, and a relative vulnerability zoning then divided. The results show that:there is a large inter-annual variation of the SSVI, especially during the later of the first ten year of21st century (2005-2009), which is related to the increasing frequency and intensity of extreme weather and climate events under the condition of global climate change; the SSVI of each five years, it is larger from1990to1994and1995to1999than from2000to2004and2005to2009, and this is closely related to the frequent activity of tropical cyclone with the same period. Spatially, the maximum, the total SSVI of five years and twenty years have the same rules, which are the high and higher level of physical vulnerability are mainly distributed in southeastern coastal provinces, the low and lower level, in northern coastal provinces, respectively, while distribution of the middle level changes greatly. The analysis also found that the contribution of the affected populations, the affected crop area, the affected aquaculture area, housing damage and direct economic loss are large to the physical vulnerability of storm surge disasters.(2) On the basis of physical vulnerability assessment, sixty indicators are selected as an index, and then the principal component analysis is used to assess the social vulnerability of storm surge disasters of the fifty-three cities along the coast. Eight principal factors are extracted as technology investments,infrastructure and information,services, region wealth, social security, population, urbanization, environment, occupation and development, which explained84.92% of the variance of the original indicators. Additive model is used to calculate the social vulnerability score of each city, and five relative levels are divided according to the standard deviation on behalf of low, lower, medium, higher, and high level, then regionalization. The results show that:most of the coastal cities are in the medium vulnerability level; Shanghai, Guangzhou, Tianjin and Shenzhen are the four cities with the low level of social vulnerability, and the indicators represent technology investments, information technology level, infrastructure and regional wealth have larger contributions, which indicates a strong disaster absorption and resilience; cities with higher level social vulnerability are mainly located in the southeast coast of China, they are Guangdong and Hainan Province and Guangxi Zhuang Nationality Autonomous, the principal factors of population, urbanization and development are main contributors; Panjin City of Liaoning Province has the high level vulnerability, and occupation is the biggest devotee.(3) Firstly, assigned SSVI value of each province to the coastal cities they contains respectively; then three kinds of weight combination of physical and social vulnerability conduct to evaluate the relative comprehensive vulnerability level of each city using the Hazards-of-Places Model, and regionalize. Here are the results:the comprehensive vulnerability level has the same trend under three kinds of different weight combination that is the southeast higher than northern coastal cities, and the physical, the social and the comprehensive vulnerability are in consistence. The composite vulnerability level are mostly moderate while the physical vulnerability weight dominated in the coastal cities of Zhejiang, Guangxi and Fujian, which shows a larger reconciliations from social vulnerability; and this indicates the effects of disasters prevention and mitigation from socio-economic elements when reducing its weight, while its physical vulnerability relatively higher. Three kinds of vulnerability are higher in the cities from Guangdong; mostly, the effects of disasters prevention and mitigation from socio-economic elements are not obvious in addition to cities such as Guangzhou and Shenzhen, which is closely related to the high frequency of storm surges, that's the greater impacts of natural vulnerability. Except Qingdao and Dalian, the composite vulnerability of most cities of Shandong and Liaoning changes along with the vulnerability changes of dominant weight; the changes like this indicate the prevention and mitigation of socio-economic factors, also relate to the fact that the region is another area influenced seriously by storm surge disasters. Shanghai and Tianjin have the low level in three kinds of vulnerability, because of strong effects of disaster prevention and mitigation while small impacts of storm surge disasters relatively.The study focused on the the coastal areas of China, and that's a large scale. Systematic analysis, composite assessment and regionalization on storm surge disasters vulnerability are carried out. The physical social and comprehensive vulnerability are combined with mathematical statistical method based on history of disaster and the principal factor analysis of indicators system, also their temporal-spatial variation and influence factors are discussed. More in-depth and meticulous researches are needed to carry out disaster prevention and mitigation of storm surge effectively, such as storm surge vulnerability analysis and assessment carried out in community scale, which could provide a scientific basis for the development of effective and targeted countermeasures to reduce vulnerability.