Risk assessment of flood disaster in Shanghai based on spatial–temporal characteristics analysis from 251 to 2000

As one of the top 20 cities exposed to flood disasters, Shanghai is particularly vulnerable because it is exposed to powerful floods and poorly prepared. However, it is unclear to understand the evolution process of floods and the variation of flood risk in Shanghai during the past 1,000 years. This paper analyzed the spatial–temporal characteristics of flood disaster and evaluated the integrated risk of flood disaster in Shanghai based on the historical flood data from 251 to 2000. The results show that flood disaster in Shanghai was divided into storm surge-induced flood, rainstorm-induced flood and overbank flood. Flood disaster in Shanghai presents rising trend with time and mainly occurs in summer and autumn. Moreover, the flood disaster is dominated by rainstorm-induced flood, especially after the establishment of the People’s Republic of China in 1949. Additionally, flood risk in different areas of Shanghai between the years 251–1949 and 1950–2000 changed significantly. Shanghai urban area, Jinshan District and Chongming County belong to increased flood risk area; Baoshan, Jiading, Qingpu, Songjiang, Fengxian, Pudong and Minhang District belong to decreased flood risk area. The integrated risk of flood disaster in Shanghai has presented spatial disparities evidently at present. Shanghai urban area is most likely to suffer flood disaster; Baoshan, Jiading and Minhang District have medium flood risk rank; and Jinshan, Songjiang, Fengxian, Pudong, Qingpu and Chongming County show low flood risk at present. The combined effect of urbanization, sea-level rise, land subsidence and the poor capacity of flood prevention facilities will give rise to the risk of flood in the next several decades. These results provide very important information for the local government to improve flood risk management.