THE EFFECTIVENESS OF MANAGED RETREAT AND COMMUNITY RELOCATION AS A FLOOD MITIGATION MEASURE IN SMALL MIDWEST COMMUNITIES

Flood damages are estimated to increase 20 fold by the end of the 21^st century due to the effects of climate change, structural flood protection, and development within flood-prone areas. Managed retreat is a method of hazard mitigation that involves moving structures away from at-risk areas. Often this involves wholesale relocation, where an entire community is physically moved or rebuilt together on higher ground. Over the last century, over 30 managed retreat community relocations (MRCRs) have been implemented in the United States, and the approach is currently being discussed as an environmentally friendly and cost-effective mitigation strategy for small, flood-prone communities. We have assembled a database of known MRCRs throughout the United States.

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. We developed three quantitative metrics to assess the success of each relocation: 1) population trends before and after the relocation, gathered from US Census data; 2) trends in home sales price per square foot derived from Zillow’s Transaction and Assessment data set (ZTRAX); and 3) loss avoidance estimates for each relocation calculated using Hazus and Lisflood software applied to structure surveys mapped in the field in July of 2018. Preliminary findings show that: 1) relocations help population retention in a majority of towns, at least compared to similar non-move communities; and 2) rural Midwest communities outside of FEMA designated flood zones have experienced more population growth than similar towns within flood zones since the 1960s. Our results seek to offer communities, planners, floodplain managers, and other stakeholders with insight into the effectiveness and feasibility of MRCR.