Assessing managed flood retreat and community relocation in the Midwest USA

Abstract

Managed retreat involves the relocation of structures or abandonment of land to manage natural-hazard risk. In the USA, a number of towns have completed or are planning partial or complete relocations. This study focuses on a subset of these towns located in the US Midwest, each relocated out of FEMA designated flood zones to mitigate riverine flooding risk. Past community relocations hold hard-won lessons for future managed retreat projects. Three pragmatic and preliminary metrics were developed here: (1) flood losses avoided, (2) population trends, and (3) trends in home sales prices. Flood-loss modeling shows that community relocation can be cost-effective, reducing economic flood exposure by over 95%. Analysis of population data and residential real-estate sales shows that Midwestern floodplain towns have lagged non- floodplain towns, and homes on mapped floodplains have sold at a discount to non-floodplain homes since at least the early 1990s. Relocation off the floodplain removed the stigma of flooding and quantifiably reenergized those communities. Relocation projects cost more than buyouts without relocation but maintain social bonds and represent a tangible investment in future resilience. Future relocation projects, including retreat from both floodplains and coasts, should draw from the wealth of empirical data and lessons learned from past retreat efforts.