Millions of Americans’ are raising homes as climate crisis floods become worse & more frequent, but how high is high enough?

Millions of Americans have properties facing the threat of destructive floods, with a cost of up to $25,000 in damages for just one inch of floodwater.

To manage that risk, people who live in areas designated as river flood zones often seek to raise their homes—but exactly how high to elevate their homes is both a critical and complicated decision.

Now, new research supported by NOAA’s Climate Program Office (CPO) and led by Penn State University suggests that, in the face of economic, engineering, and environmental uncertainties, homeowners would reduce the most damage by raising their homes beyond the minimum guidelines recommended by the Federal Emergency Management Agency (FEMA).

ABSTRACT:

Homeowners around the world elevate houses to manage flood risks. Deciding how high to elevate a house poses a nontrivial decision problem.

The U.S. Federal Emergency Management Agency (FEMA) recommends elevating existing houses to the Base Flood Elevation (the elevation of the 100-year flood) plus a freeboard. This recommendation neglects many uncertainties.

Here, we analyze a case-study of riverine flood risk management using a multi-objective robust decision-making framework in the face of deep uncertainties. While the quantitative results are location-specific, the approach and overall insights are generalizable.

We find strong interactions between the economic, engineering, and Earth science uncertainties, illustrating the need for expanding on previous integrated analyses to further understand the nature and strength of these connections.

Considering deep uncertainties surrounding flood hazards, the discount rate, the house lifetime, and the fragility can increase the economically optimal house elevation to values well above FEMA’s recommendation.

Photo is by Marvin Nauman/FEMA in Sultan, Washington, Nov. 11, 2006.

See full research paper in Nature Communications.

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