Mapping flooding risks in Changsha with a GIS-based approach

This study introduces Triangular Fuzzy Number-based Analytical Hierarchy Process (TFN-AHP) with the GIS method to assess flood risk in Changsha City, China. A novel research framework of hazard, exposure, vulnerability, and flood protection was employed to study Changsha's flooding risks. The indexes included climate, terrain, and social-economic data, river network proximity, elevation, slope, land use, road network proximity, population, GDP, and flood prevention measures. Weighs of each index were calculated with TFN-AHP. The study generated flood risk distribution for each index and overlaid the layers with GIS to produce hazard, exposure, vulnerability, and flood protection maps. Finally, monthly flooding risk distribution was generated to analyze the patterns of flooding risk in Changsha. The results show that the risk level of flood disasters in Changsha City gradually decreases from the mainstream of each river to both sides. In general, the urban flooding risk decrease from the central urban area to the suburban areas. The western and eastern suburbs display different trends: In the rainy season, the belt from Ning Xiang downtown, passing Dachengqiao Town, Hengshi Town, to Huangcai Town and Yuelu south part of downtown, tends to be more prone to flooding; however, the effect of high hazard in the eastern suburb was mitigated by exposure, social economic and flood control indexes