Future Population Exposure to Flood Risk: A Decomposition Approach across Shared-Socioeconomic Pathways (SSPs)

Abstract

Extreme weather events, such as flooding, are expected to become more severe due to climate change. These impacts are connected to impacts on human systems including economic, social, and political crises. Adding to the challenge, populations have concurrently settled in risky areas that were previously thought to have low, or no, exposure. As such, it is important to understand how population exposure to flooding may change over time. Here, we build on existing research to project future populations with their demographic components under all five Shared Socioeconomic Pathways (SSPs) at the block group level across the US. These projections are evaluated with future flood projections to characterize exposure changes over time. Broadly, across the five SSPs, the most increase in exposure will occur in SSP5 (+470,719), and the least will occur in SSP 3 (+57,189). Across all five SSPs, we find that there will be significant increases in expected annual exposure for populations 80 years and older, with an increase in exposure by approximately 216% under SSP5. By decomposing the contributions from flood and population growth, we find that the population growth induced effect contributed to an increase in the population exposure for all of the SSPs except for SSP3. In SSP5, this effect was the largest (+72.7% more exposure), while in SSP3, the population effect decreased the overall exposure by 83.5%.