America Could Spend $400 Billion on a Wall to Hold Back the Rising Seas—and It Might Not Be Enough

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At the end of the day, everything about climate change is a choice. And among the most serious choices are the ones we’ll face are along our coasts.

A new report and interactive website released on Thursday by the Center for Climate Integrity lays out some the stakes for increasingly inundated coastal communities. The group’s estimates show that to defend every coastal city, town, and hamlet in the U.S. with sea walls over the next 20 years could cost $416 billion under a fairly optimistic climate scenario. Some small communities would incur cost upwards of $1 million per resident while big cities would be looking at huge, multi-billion dollar projects.


The findings reveal the uncomfortable truth that we likely won’t be able to save everything. That means in the coming decades communities will likely be forced to choose whose house is saved, whose is turned over to the rising tides, and who pays for those decisions.


The report maps out what would happen to every coastal community in the U.S. in terms of flood frequency as seas rise. It uses sea level rise projections under RCP4.5, a climate scenario where the world’s emissions peak by midcentury, after which we begin drawing down emissions and limit warming to about 2.4 degrees Celsius (4.3 degrees Fahrenheit). This is something the world is nowhere close to on track to do and sea level rise projections keep getting more dire, but hey dare to dream.

The study also uses a one-year storm surge estimate, which is basically the type of flooding you’d expect every year as opposed to your Sandys and Michaels, hurricanes which delivered storm surge likely to occur only every few hundred years. Again, this underscores how conservative the analysis is since those types of high impact flooding events can send water streaming much further inland and are becoming more common as seas rise.


Using this setup, the researchers estimated how much protection would be needed for coastal communities and inland ones that can see flooding when storm surge comes in. By the numbers alone, the results are staggering. The cost to protect all coastal communities would be $416 billion by 2040. It would require building 50,000 miles of barriers to hold back the sea.

But building those walls is a risky, expensive, and ecologically disruptive choice. Sea walls cut off important natural processes and can help speed up erosion by amplifying wave action. And they may lead to complacency for people living behind them with disastrous consequences.


“It’s a dangerous thing you see a lot with adaptation, to think we can just engineer our way out of this by holding the oceans back,” Andrea Dutton, a sea level rise researcher at the University of Florida, told Earther. “No we can’t. I’m a geologist. Ice sheets can respond very quickly to warming. We’ve see what living in a bowl is like for people living in New Orleans and what happens when those walls are breached [during Hurricane Katrina]. It’s scary to me. Is that something we want to be pursuing?”

On the cost front, the report notes that Big Oil and other historical polluters could pay. That’s something a few municipalities have tried to make happen through the legal system, though they haven’t had any victories yet. Absent that, federal money could fill some gaps and Dutton noted that counties could help pool resources for protection, as is happening in Southeast Florida.


But if we’re being honest, putting every place behind a sea wall—even walls that are inadequate for when big storms come—just isn’t feasible. Bob Kopp, a sea level rise researcher at Rutgers, told Earther that in the coming decades, we’ll likely see communities turning to “various mixtures of soft protection, accommodation of more frequent flooding, and managed retreat.”

Deciding who gets what protection and who gets paid how much to retreat are huge questions. Wealthier communities along the coast, like Miami Beach, have been able to undertake multibillion dollar projects including raising streets and installing massive storm barriers. But in places like Cameron, Louisiana (per capita income $13,499, per capita cost of protection $870,000), the local government’s ability to fund protection infrastructure is likely to be limited. It’s likely we’ll see poorer communities being forced to retreat inland away from the ocean, something that’s already begun from Louisiana to Staten Island. And that raises questions about what a just transition for coastal communities looks like, including processing what it means to lose your home.


“We talk about science, we talk about economics,” Dutton said. “What about the grief that goes along with that?”