Assessing future flood risks in megacity suburbs under shared socioeconomic pathways (SSPs) scenarios: A case study of Beijing

Climate change increases the frequency and intensity of extreme storm events, causing increasing flood challenges to the cities, especially for the urban fringe of megacities. This paper aims to explore the future flood risk under climate change by three Shared Socioeconomic Pathways (SSPs) scenarios, focusing on Beijing's suburbs as a case study. Using a GIS-based Soil Conservation Service Curve Number (SCS-CN) method, this paper simulated the submerge areas and compared the flood risks between historical (1900-2021) and projected (2021-2099) periods under SSP1-19, SSP2-45, and SSP5-85 scenarios. The results show a 1.18-fold increase in flood risk by 2099, but it was unevenly distributed. According to the simulated flood submerge area maps, the size of the submerged area is projected to increase by nearly 1.5 times compared to its current size. The sub-urban townships located in Huairou and Yanqing Districts, along with those located in the upper watershed area of the Baihe River, will experience a notable rise in flood risk in 2021-2099. These findings can provide a theoretical basis for climate adaptation actions and policies for the sub-urban area of Beijing.