Research On The Urban Flood Vulnerability Quantitative Model And Its Dynamic Evolution

The frequent occurrence of flood disaster in recently years illustrates that urban flood disaster is no longer just a product of flood events caused by the natural phenomenon, but it is seen as the social phenomenon caused by the interaction mechanism between flood events and the urban vulnerability. More and more hazard bearing body in the city is in the flood hazard areas, while the urban vulnerability "zoom" the effect of flood events, exacerbating the possible of the economic losses and the impact of flood events on the cities. And increasingly frequent urban floods, resulting in "urban flood risk", or "the probability of the potential urban flood events occurred in a given time period and area" become increasingly random, fluctuations, and unpredictable. And "Urban flood vulnerability" as the inherent internal attributes of city, namely "the extent of loss of cities facing with flood disaster", researching it can be used to identify "vulnerable areas" or "weak groups" of cities, these areas and groups need to take emergency rescue measures in advance. This will avoid the disastrous consequences may caused by flood disaster, which will become the core of "the political early warning system" in the future construction of urban flood control system.However, the existing research of urban flood vulnerability mainly focus on the assessment and analysis of a particular factor constituting the urban flood vulnerability system or a particular time to study the degree of urban flood vulnerability, lacking the systematic research of urban flood vulnerability theory and method, caused most research results are difficult to apply and promote. And most research methods are descriptive macroscopic, lacking quantitative and operational research methods. Therefore, in order to improve the ability of cities to adapt and resist the growing number of flood disaster, it is necessary to quantitative and systemic research the urban flood vulnerability system, especially researching the dynamic evolution of urban floods vulnerability with the changes over time and space, including quantifying the impact of land-use changes and extreme rainfall events these important factors on urban flood vulnerability, but there is seldom literature currently related to the above research contents.This article will be based on the some related theories and conceptual models of urban flood vulnerability, using a variety of research methods, such as the improved C-NCSA algorithm, a series of the evolution models of land-use change characteristics and rainfall characteristics, the gray system dynamic model, generalized Pareto model, and the qualitative methods combined with the quantitative methods, innovative proposed the quantitative model of urban flood vulnerability. And researching some cutting-edge topics, such as based on the land-use changes to study the dynamic evolution of urban flood vulnerability, and the impact of extreme rainfall events on urban flood human vulnerability, and ultimately drawing a series of urban flood vulnerability maps based on different times, different flood depths and different land-use scenarios.Firstly, constructing a quantitative model of urban flood vulnerability. By scientific setting the core elements constituted of urban flood vulnerability system, including urban flood exposure and sensitivity, to explore the relationship and interaction coupling mechanism between these two core elements. Construct the quantitative model of urban flood vulnerability, and quantitatively calculate the value of vulnerability of each unit regional in urban flood hazard areas, and use the improved C-NCSA algorithm to cluster the value of vulnerability. Through the GIS software, drawing a series of vulnerability maps of urban flood hazard areas in different flood depths, to determine the degree of vulnerability of the whole flood hazard areas and the particular "vulnerability" region.Secondly, exploring the dynamic evolution of urban flood vulnerability based on land-use changes. Through proposing the response mechanism between land-use changes and urban flood vulnerability, determine the clear causal relationship between land-use changes and urban flood vulnerability. Building a series of detection models of the evolution of land-use change characteristics, to monitor the heterogeneity, dominance and aggregation of each land-use type in urban flood hazard areas in different periods. Using the quantitative model of urban flood vulnerability to simulate and analyze the value of flood vulnerability in different periods of time, different submerged depth and different land use scenarios, and draw a series of vulnerability maps of urban flood hazard areas to determine the influence of land-use changes on urban flood vulnerability. And using the analysis model of evolution trend of urban flood vulnerability which is built based on the gray system dynamics model, to predict the outlook the evolution trend of vulnerability in urban flood hazard areas.At last, analyze the influence of extreme rainfall events on urban flood human vulnerability. Through proposed a series of detection models of the rainfall characteristics, including the feature model of rainfall trend, the feature model of rainfall mutation, to detect the evolution processes of the city’s historic rainfall characteristics, such as the whole trend of rainfall and the mutated year of rainfall. And based on the generalized Pareto model, building the fitting model of the probability of extreme rainfall events to fit and forecast the probability of extreme rainfall events with different magnitudes in different historical periods. In addition, building the model of impact of extreme rainfall events on urban flood human vulnerability, by respectively proposed the rainfall feature parameters which elaborate the physical characteristics of extreme rainfall events, including response time, rainfall characteristics, and the duration of rainfall, as well as the feature parameters of urban flood human vulnerability, including age and gender, to quantitative analysis the impact of different rainfall feature parameters on the human vulnerability of different groups, in order to determine the "vulnerable groups" in urban flood human vulnerability, as well as which rainfall feature parameters in the extreme rainfall events have a decisive influence on the human vulnerability of different groups.The quantitative model of urban flood vulnerability we proposed in this paper, in order to investigate the dynamic evolution processes of urban flood vulnerability based on land-use changes, and analyze the influence of extreme rainfall events on urban flood human vulnerability. It aims at filling the gaps in the current research on the quantitative analysis and dynamic evolution of urban flood vulnerability. It is expected to provide a scientific and effective technical support for our country to construct flood control system based on "flood risk management", and for the government policy-makers to explore the spatial planning and economic development based on flood risk management.