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Photo by Sandro Kradolfer​​

Rising Seas

​Major storms like Hurricane Katrina and Hurricane Harvey have cost billions in flood damage. But U.S. coastal areas are vulnerable to flooding even absent major storms, due to sea level rise driven primarily by climate change. And this vulnerability will have major ramifications for future emergency preparedness plans.

In fact, chronic and disruptive flooding caused by rising sea levels will put approximately $136 billion worth of U.S. homes and commercial properties at risk in the next three decades, according to Underwater: Rising Seas, Chronic Floods, and the Implications for U.S. Coastal Real Estate, a recently released report from the Union of Concerned Scientists (UCS).

This means that more than 300,000 of today's homes and commercial properties in the contiguous United States would be at risk between now and 2045, according to the report. By the end of the century, that number would grow to nearly 2.5 million residential and commercial properties—collectively valued at $1.07 trillion—at risk of chronic, disruptive flooding. (The report defines chronic and disruptive flooding as flooding that occurs 26 times per year or more.)

A few areas would be hit especially hard. States with the most homes at risk by the end of the century are Florida, with about 1 million homes (more than 10 percent of existing homes); New Jersey, 250,000 homes; and New York, 143,000 homes.

Moreover, the cost estimates do not include infrastructure losses. Roads, bridges, power plants, airports, ports, public buildings, military bases, and other critical infrastructure along the coast also face the risk of chronic inundation. 

"The direct costs of replacing, repairing, strengthening, or relocating infrastructure are not captured in our analysis, nor do we account for the indirect costs of flooded infrastructure, including disruptions to commerce and daily life," the authors write. "Taken together, these costs of chronic flooding of our coastal built environment—both property and infrastructure—could have staggering economic impacts."

The risk itself is not the only troubling issue, the study finds. There is a "gap in awareness" of the risk because it is not being communicated properly. "The information is inadequately reflected in the Federal Emergency Management Agency's (FEMA) flood risk maps, for example, which only account for present-day flood risks," the authors write.

And although some individual states have standards requiring real estate agents and home sellers to disclose flood risks at the time of a home sale, there are no uniform and robust national requirements. Lenders and investors are often largely unaware of growing tidal flood risks to properties.

Given this, UCS is calling for the federal government to take a lead role in getting the message out on future flood risk. FEMA's flood maps—which help set flood insurance rates, guide local land-use policies, and inform infrastructure design standards—must be updated to reflect sea level rise projections, the authors argue. National standards for flood-risk disclosure for all real estate trans­actions are needed.

Finally, instead of rebuilding current coastal developments with disaster relief payments, government investments should be made with a view to reducing future risks through a range of protective measures, such as home buyouts and new floodproofing measures, the report argues.