Exploring The Spatio-temporal Patterns Of Impervious Layer In Wuhan And Its Application In The Analysis Of Urban Waterlogging

With the rapid development of urbanization,impervious layer influences urban surface runoff,relates closely with urban waterlogging,and is one of the key element which should be controlled and planned strictly in the development of low impact.In the sponge city construction of Wuhan,the investigation and statistics of the impervious layer is still lacked.It is nessesary to understand the spatio-temporal patterns of impervious layer and grasp the construction mode of Wuhan,which can help give consideration to the needs of urban expansion and solve the problem of waterlogging.This paper oriented on the practical requirements for the sponge city construction of Wuhan,responded the requirements of reducing and reconstructing impervious layer,give full play to the professional advantages of GIS and remote sensing,utilized geographic national conditions monitoring data of Wuhan from 2015-2016 to extract the impervious surface and explore the spatio-temporal patterns of impervious layer in Wuhan and its application in the analysis of urban waterlogging.The paper analyzed the spatio-temporal patterns and change patterns of impervious layer in Wuhan from aspects of the change patterns of the amount and distribution characteristics of the impervious layer,the transformation characteristics among impervious layer and other land types,the expansion patterns of urban impervious layer and the urban impervious landscape pattern,with the aim of conducting reliable assessments of the land use and urbanization process of Wuhan.Based the impervious layer data,the paper studied the waterlogging causes in a waterlogging prone area of Wuhan.Different from the present analysis of the causes of waterlogging which are in favour of qualitative analysis or hard to do quantitative analysis to the interaction between factors,the paper used the analysis method of spatial difference analysis and utilized the GeogDetector to analyze the dominant factors leading to waterlogging,the correlation between factors and waterlogging,and the interactions on waterlogging among the factors,furthermore,the paper located the areas with strong interaction of waterlogging factors and put forward some suggestions for the prevention of waterlogging,with the aim of solving the problem of the difficulty in the reconstruction of the existing urban areas.The conclusions have good application value.The conclusions are as follows:(1)The impervious surface of Wuhan were expanding overall from 2015-2016,the regions where impervious surface area decreased concentrated in the central urban area,and the expansion intensity of impervious surface increased from downtown to suburbs;the area of impervious surface,bare soil and water's space in Wuhan increased from 2015-2016,while the green space area decreased only,besides,the area of impervious surface and green space changed more significantly;the expanded impervious surface patches were relatively small and broken,they mainly distributed in the new urban area near the central city,while the reduced impervious surface patches didn't tend to concentrate around the central city,in addition,some reduced chunks of impervious surface were mainly distributed in the suburbs,they mainly converted to grassland and cultivated land,the results reflected the objective phenomenon of land agglomeration and the scale effect in the process of urbanization in Wuhan,and the thought of "guiding the flow of factors and promoting the rational allocation of resources" in Wuhan urban and rural planning.The impervious layer landscape pattern showed that the impervious layer pattern in the suburbs of Wuhan was relatively unitary,which was mainly composed of housing construction,so there is need for planning rationally for urbanization of the suburbs of Wuhan and enriching its facilities to increase the attraction.(2)The waterlogging factor with the highest power determinant values in the study area is the slope standard deviation,followed by the height standard deviation and the proportion of impervious layer area.Besides,there was no significant difference in the magnitude of power determinant values of the waterlogging factors,which indicated that the waterlogging in the study area was not dominated by a few factors,and the factors that caused waterlogging can be varied.Among all the waterlogging factors,height standard deviation,slope standard deviation,slope gradient,impervious layer isolation,impervious layer fragmentation,proportion of permeable surface area and proportion of water area were neatively correlated with the severity of waterlogging;proportion of impervious layer area,surface runoff coefficient and density of underground rainwater drainage network were positively correlated with the severity of waterlogging;and there was no obvious correlation between elevation and the severity of waterlogging.All the interactions among the waterlogging factors enhanced the severity of waterlogging.The interactive effect of waterlogging factors in the study area could be divided into two types,one was caused by the interaction of low-flat terrain,low infiltration capacity of surface(a large proportion of impervious layer area or high surface runoff coefficient)and the compact distribution of impervious layer,the other was caused by the interaction of steep terrain,low density of underground rainwater drainage network and a large proportion of impervious layer in some land.The waterlogging causes of all the areas with waterlogging problems were excavated,and the recommendations of governance waterlogging were provided.