| In recent years,in the context of rapid urbanization and frequent extreme weather,due to the lack of sufficient understanding of the function of urban wetlands,a large number of urban wetlands are used for development and construction in the process of rapid urbanization,resulting in the reduction of urban wetland area,the reduction of hydrological connectivity,and the lack of urban drainage system capacity,frequent urban waterlogging disasters.To explore the impact of urban wetland landscape dynamic change on urban waterlogging disaster,this paper selects nine large and medium-sized cities in China,such as Beijing,Wuhan,Changchun,etc.,as the research object,uses multi-source remote sensing and GIS technology,and adopts the method of human-computer interaction to extract the spatial and temporal dynamic number of urban wetland in the past 50 years(four periods:1970,1990,2000,2018)in nine cities According to,and analyzes its dynamic change characteristic.On this basis,the landscape pattern and connectivity index of urban wetland were calculated by Fragstats4.2,CONEFOR 26 and other landscape software,and the impact of urban wetland change on urban waterlogging disaster was explored by Flood Area model.The main results are as follows:(1)The pattern indexes of typical wetland landscapes in 9 cities in different years were calculated.The results show that the area of urban wetland decreases year by year,the LSI and PAFRAC values of each wetland type decrease year by year,the fragmentation of urban wetland landscape becomes more and more serious,the complexity of shape and structure decreases,and tends to simple shape;the number of natural wetland decreases,the number of human wetland increases;the dominance of wetland landscape decreases.(2)Many ecological functions of urban wetlands are realized through hydrological connectivity.According to the changing trend of wetland overall connectivity index in the past 50 years from 1970 to 2018,Qinhuangdao has slightly increased,while Tianjin,Hefei,and Chengdu have little change,while Hangzhou,Nanchang,Beijing,Wuhan,and Changchun have all shown a downward trend.Among them,Hangzhou has the largest decline(-0.256),followed by Beijing(-0.096))Wuhan(-0.071).The continuous decline of the overall connectivity of the urban wetland landscape indicates that the urban wetland is isolated and isolated in the process of urbanization,and its hydrological function will inevitably be affected,which is one of the background reasons for the frequent occurrence of urban waterlogging disaster.(3)In the past 50 years,wetlands in 9 cities have been developed into construction land in varying degrees,and the original wetland is also prone to become the city's waterlogging disaster-prone area because of its low terrain.Using spatial analysis,the shortest distance between these 9 urban waterlogging disaster points and wetland loss patches was obtained.The results showed that 25.2%of waterlogging disaster points occurred in the occupied wetland location,and more than 77%of waterlogging disaster points occurred within 300 meters of the occupied wetland.(4)The accuracy test and risk assessment of the simulation results of the Flood Area model under different return periods were carried out.It was found that the simulation results were also highly consistent with the distribution of urban waterlogging disaster points.The inundated area of residence,green land,and road in the 100-year return period scenario is 3.8 times,4.46 times,and 29.11 times of that in the 10-year return period scenario.With the increase of the return period,the risk of urban waterlogging is also increased.These results are helpful to understand the background of waterlogging disasters and provide more scientific data and theoretical support for the management,construction,and utilization of urban wetlands. |
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