The Impact of Urban Spatial Expansion on Regional Environment of Flood Hazards Gestation: A Cace Study in Jiangning District of Nanjing City
城市空间扩展对区域洪涝孕灾环境的影响

The urban spatial growth directly changes the flood hazards inducing environments such as impervious surface, river landscape, which leads to the disorder of runoff process and floods disaster. This paper emphasizes on measuring and analyzing the impact of urban spatial growth on flood hazards inducing environments during the urbanization process of Jiangning Economic and Technological Development Zone based on the data from remote sensing images, hydrological and urban planning, and the analysis tools of Geographic Information System (GIS), site investigation and modeling. The statistics show that since 2000 urban spatial growth has been particularly rapid, and the area of urban construction land has increased by nearly four times; the water surface area rate has dropped by 50%; the spatial growth models have transmitted local infill development with cluster pattern into large-scale expansion in urban outer areas; the rate of impervious surface areas throughout the whole study area is 48.12% now, and the mean impervious surface area rate of construction land is over 70%. Therefore, the impervious surface rate, runoff paths and river landscape features have been evidently changed by the urban spatial growth. The analysis of DEM data show that Yin-Xiang region near the eastern outlet of Jiulong Lake and the area surrounding Niushou, Jiangjun and Cuiping mountains mostly tend to form flood hazards. In addition, the intersection area of Jiangjun Road-Tianyuan Road, the intersection area between Niushou river and Jiangjun Road and the region of Yin-Xiang are regarded as the most sensitive areas that induce flood hazards, and the area along Jiangjun Road and Focheng Road is of higher sensitivity. The results can serve as references for hydrological safety of land use arrangement and the construction of flood prevention system.