Climate adaptation

Past US floods give lessons in retreat

The movement of people and infrastructure out of vulnerable areas, a process called managed retreat, is gaining recognition as a potential adaptation strategy to climate change and natural hazards (see also M. Hino et al. Nature Clim. Change 7, 364–370; 2017). Although research into the effectiveness of this process is scarce, the long history of retreat in US flood management offers some useful lessons.

In 1993, the US Congress amended the Robert T. Stafford Disaster Relief and Emergency Assistance Act to authorize the Federal Emergency Management Agency to purchase vulnerable properties and encourage retreat. Since then, the agency has purchased roughly 38,500 properties in 44 states. Acquired buildings were destroyed to create open public spaces.

Retreat in even small numbers can have a large effect. After Hurricane Sandy in 2012, New York state acquired just 300 out of 10,000 damaged homes, but removed two entire neighbourhoods. Whole towns have relocated too, including Pattonsburg in Missouri, Valmeyer in Illinois and Soldiers Grove in Wisconsin.

Such cases can provide guidance on when to retreat, where to relocate and how to coordinate state and federal agencies. Scientists should evaluate past initiatives to identify best practices for the future, when managed retreat may need to be executed on even larger scales.

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Correspondence to A. R. Siders.

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Siders, A. Past US floods give lessons in retreat. Nature 548, 281 (2017).

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