Analysis And Strategy Research Of Coastal Urban Mitigation Guided By Resilience Goal

Most urban populations around the world live in the coastal cities that are in direct geographical relationship with ocean.That is to say,the urbanization must face strong challenges with increase in population.As the complicated social ecosystem,coastal cities not only need to witness the gradually subtle change man-earth relationship,but also shall solve the issues influencing city stability,such as climate change,social security,economic turmoil and catastrophe risk,etc.For this reason,how to properly carry our urban mitigation is the key to guarantee quality of urban life in the future.In order to solve the difficulty of comprehensive mitigation in coastal cities,this dissertation takes the urban resilience that is discussed heatedly in planning field as direction,researches on urban resilience mitigation and develops the diversified mitigation strategy for coastal cities.Based on the quantitative analysis of the research achievements of urban resilience and urban mitigation via Citespace,this dissertation combined with their internal relation.It proposes that urban resilience mitigation maintains the long-term stability of urban system via the measures on disaster inducing environment and hazard-affected body.From the perspectives of disaster inducing environment and hazard-affected body,and directing at the three different development stages of urban resilience,this dissertation puts forward the coastal cities’mitigation demand mainly focusing on engineering resilience,ecological resilience,economic resilience,social resilience,community resilience and resilience governance.On this foundation,the resilience mitigation framework for coastal cities are proposed,including enhancing the adaptation of disaster inducing environment to ensure the orderly operation of cities,reducing vulnerability of hazard-affected body to control the influence of urban disaster,and analyzing urban resilience mitigation ability to stabilize urban development.The enhancement of adaptation of disaster inducing environment contains two parts of natural environment and social environment.In natural environment,the climate and environment adaptability is improved by analyzing climate adaptability,setting climate elasticity indexes and enhancing public participation;hydrological environment adaptability is improved by controlling pollution,cultivating awareness of flood risk and implementing water circulation management;the adaptability of ecological environment is improved jointly through the ecological elastic mechanism,ecological restoration mechanism and ecological commemorative mechanism;the adaptability of green infrastructure is improved by identifying hot spots of disaster mitigation and building planning model.In the social environment,open space adaptability is improved by defining the function of open space and formulating flexible planning methods;the uncertainty of future disaster is affirmed by formulating mitigation vehicles and pedestrian evacuation models;business environment adaptability is improved by developing flexible retail management regulations and strengthening supply network stability.In terms of reducing the vulnerability of hazard-affected body,the vulnerability of supply chains of mitigation materials is lowered by confirming the supply subject of mitigation materials,increasing supply levels of material demand and supply sides,and arranging supply support systems;infrastructure vulnerability is reduced by improving mitigation projects and proposing flexible planning methods;the vulnerability of city economy is reduced by clarifying the relationship between catastrophe insurance system and risks,and promoting mitigation revolution of catastrophic insurance;community vulnerability is reduced by continuously rehabilitating the quality of life,advancing community wisdom contraction,and setting up mitigation centers.On the basis of above argumentation,the adaptation-vulnerability based index system and assessment model for evaluating the resilience mitigation ability of coastal cities are established.Taking Tianjin as example,the statistical data and spatial data are collected by regarding street as spatial unit,disaster inducing environmental adaptability and hazard-affected body as criteria layer and mitigation related argumentation contents as element layer,24 indexes are proposed and the score of Tianjin’s resilience mitigation ability is obtained via principal component analysis.Besides,cluster analysis,space autocorrelation analysis,etc.are applied to know the self-correlation between resilience mitigation ability and spatial unit.The analysis results show that,the resilience mitigation ability in Tianjin shows aggregation pheromone in spatial distribution,but it is weakly related to the spatial pattern in master plan and there is no randomness in mitigation ability distribution.Meanwhile,urban resilience mitigation ability has no correlation in space.This adaptation-vulnerability based resilience mitigation ability of Tianjin can enhance the pertinence of urban mitigation;meanwhile,taking street as research objective can promote research precision in the recognition of spatial pattern.According to the evaluation of adaptation vulnerability and resilience,the corresponding strategies aiming at the difference of streets’resilience mitigation abilities is raised.Finally,the modeling respectively for open space and urban traffic with higher factor weight in evaluation model is carried out,and the analogue simulation based on vehicle evacuation as well as pedestrian evacuation is conducted to go deep into the uncertainty of resilience mitigation of Tianjin in the future.With respect to vehicle evacuation,this dissertation simulates three different situations based on Vissim software,including normal evacuation without traffic control,optimal path evacuation under traffic control,and phased evacuation under traffic control.According to the two variables（evacuation time and vehicle density）in different situations,the evacuation efficiency of phased evacuation under traffic control is the highest.The optimal path evacuation under normal evacuation thinking has inferior evacuation effect to that of phased evacuation due to unpredictable traffic pressure during emergency evacuation.In pedestrian evacuation,this dissertation applies Pathfinder software to create three different situations ofα_{road width}=x andβpopulation density=y,αroad width=x/2 andβpopulation density=y,αroad width=x andβpopulation density=y/2for simulation.The analysis results of five indicators,such as population density,road use intensity,standard speed,cumulative population flow and evacuation route,show that the pedestrian evacuation efficiency is the highest in situation ofα_{road width}=x andβ_{population density}=y.It indicates that road width is positively correlated to evacuation efficiency,while population density has no obvious relationship with the evacuation efficiency within the acceptable range.During the simulation of pedestrian simulation,it is found that there is switching phenomenon in the equilibrium of urban resilience,which verified the existence of resilience threshold value.Directing at the above simulation results,the mitigation strategy targeted for urban traffic management and open space is proposed,along with the diverse mitigation paths for Tianjin in planning,technology and governance.