Coastal communities in the contiguous United States face more than $400 billion in costs over the next 20 years to defend coastal communities from sea-level rise, according to a report released recently by the Center for Climate Integrity in partnership with the engineering firm, Resilient Analytics.

This is approaching the cost of the original interstate highway system and will require the construction of more than 50,000 miles of coastal barriers in 22 states by 2040 — half the time it took to create the nation’s iconic roadway network.

The first-of-its-kind report titled, “High Tide Tax: The Price to Protect Coastal Communities from Rising Seas” includes rankings of the estimated sea-level rise adaptation costs by city, county, congressional district and state. Using moderate (not worst-case) sea-level rise projections for the year 2040 and storm surge expected to be seen every year, the report identified 132 counties where costs will exceed $1 billion, and 14 states where costs for these minimal defenses will exceed $10 billion. The complete rankings can be found here.

For hundreds of small coastal and tidal communities identified in the report, the costs will far outstrip their ability to pay, making retreat and abandonment the only viable option unless enormous amounts of financing emerge in a short period of time. As just one example of the scope and gravity of this problem, in 178 small communities, the cost of building basic coastal defenses is more than $100,000 per person.

Florida is by far the most heavily impacted state, with costs reaching nearly $76 billion statewide; 23 counties facing at least $1 billion in seawall expenses alone; and 24 communities where building this rudimentary level of coastal protection will cost more than $100,000 per person.

“Our collective failure to come to grips with the massive costs of climate adaptation is the latest, and most delusional form of climate denial,” says Richard Wiles, executive director of the Center for Climate Integrity.

The situation may turn out to be much worse. Sea levels could rise more than the estimates used in the study, and experts say they’re unlikely to rise any less. And many localities will protect for more damaging storms than the modest one-year storm surge used in this analysis.

“The cost estimates presented here are just a small portion of the total adaptation costs these local and state governments will be forced to finance,” says Paul Chinowsky, lead engineer on the project.

To read the full report and view the full data set, which includes cost estimates for 2040, 2060, 2100 as well as other RCP and storm surge scenarios, visit www.climatecosts2040.org.

The Center for Climate Integrity is a project of IGSD.