Planned relocation may reduce communities’ future exposure to coastal inundation but effect varies with emission scenario and geography

The planned, permanent relocation of entire communities away from sea level rise (SLR) and coastal floods is an already occurring climate change adaptation strategy. Yet, planned relocations are fraught undertakings with multiple goals, and may or may not achieve their most basic objective: to reduce risk. Here we assess risk of future coastal flooding before and after moving, for three dates and three emissions scenarios, for 17 communities from a global dataset. Most communities achieved exposure reduction with less future inundation in destinations than origin sites, but the extent varies across time and emissions scenario. In all cases, origin sites have projected exposure to SLR plus a once-per-year flood, with increasing exposure under high emissions scenarios and towards 2100. In nine cases, even destination sites have projected inundation exposure under some scenarios. Small-island-to-small-island relocations had more projected inundation in destinations than moves from a small-island-to-mainland, or from mainland-to-mainland. Planned relocations reduce communities’ risk of future coastal floods, but they do not eliminate it entirely – especially under high emissions scenarios and for moves with small-island destinations, according to an analysis that combines data on relocation sites and inundation projections.