Study Estimates Seawalls to Protect U.S. Coast Will Cost $400 Billion

The spending would represent just 15% of what it will cost to protect and adapt cities to rising temperatures.

by | Jun 20, 2019

If the oceans continue to rise at the pace they have over the past two decades, sea level will rise by more than two feet—enough to overwhelm infrastructure and displace millions of people. The construction of seawalls high enough to defend coastal communities against that level of rise will cost roughly $400 billion in the next two decades for the continental U.S. alone. It will saddle 127 counties and 68 congressional districts with more than $1 billion in other expenses.

That is the tally of a study published Thursday by the Center for Climate Integrity, which identified high-risk communities likely to face the greatest costs. The authors said they hope it provides guidelines that could inform infrastructure planning in the near future.

“We’re talking about things that need to be built within the next decade to offset these impacts that are anticipated by 2040,” said Paul Chinowsky, an engineer at the University of Colorado and lead scientist for the study.

The analysis was based on monderate sea level rise over the next 20 years––assuming carbon emissions peak around 2050 then sharply decline––and is not representative of a worst-case scenario. The study said its cost estimates are conservative and account for just one piece of climate adaptation: building more than 50,000 miles of seawalls and other barriers to protect coastal cities. The study said this represents about 15 percent of the total cost associated with protecting cities from the effects of climate change, an expense that will fall to taxpayers if other sources of revenue are not found.

“For decades, we’ve been slightly disillusioned about the number of miles that need to be protected and underestimated them,” said Chinowsky. “The resources that are going to be required to do this, the amount of technical expertise and physical resources we’re going to need, is a massive national question and a conversation we need to have.” The researchers said  seawalls and other barriers against sea level rise are the most minimal proactive measures the U.S. can take.

The team constructed a searchable database that allows users to input a Zip code to see cost estimates for that area. As for the $400 billion national price tag, it’s unclear where this amount of funding will come from.

“Everyone is pointing toward the federal government but there’s no realistic option for federal or state money covering this,” said Skip Stiles, executive director of Wetlands Watch in Norfolk, Va. and coauthor of the study.

Stiles said holding polluters, including fossil fuel companies, responsible for at least some of the costs could be the most viable option.

“We have to look at the sources who actually generated this problem and look at their wealth and see if that wealth can be put into these projects,” said Stiles.

More than a dozen communities across the country have already filed climate liability suits against fossil fuel companies to recover costs associated with climate change. They hope to recover damages using state public nuisance laws that forbid companies from knowingly selling dangerous products, and fossil fuel companies, the communities emphasize, have known about the climate impact of their products for decades.

State governments including Florida, the most heavily impacted state in the study, are already developing strategies for climate resilience, though adequate funding remains a challenge. The study estimated that the construction of more than 9,000 miles of seawalls and other barriers will cost Florida nearly $76 billion by 2040. Twenty-three Floridian counties will likely need at least $1 billion, and these projects alone will cost 24 of the state’s communities $100,000 per person. Jacksonville will need to spend an estimated $3.4 billion on the infrastructure and taking into account one-year storm surges, weather events that typically occur every year, Monroe County, Fla. will need to spend $11 billion on seawalls.

Washington state is already making plans to relocate climate refugees in communities at risk of being lost. The state could spend nearly $24 billion on seawalls to defend its coastal communities.

Rural areas with a small tax base will likely be at a disadvantage when competing for federal funds. In the study’s  moderate scenario, seawall construction will cost 19 small, mostly unincorporated communities more than $1 million per person. For Dames Quarter, Md., the estimate is nearly $4 million per person. This number soars to more than $7 million per capita in Junction City, Wash., where the median household income is less than $50,000.  

“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 very short period of time,” the study concluded.

Still, relocation comes with its own set of expenses. The report notes that governments that fail to protect private property may be required to compensate property owners for the value of property abandoned due to rising sea levels.

“Whether you choose to do it with berms or sea walls, every one of those miles must have a decision made as to whether or not it will be protected,” said Curtis Spalding, a former regional administrator for the Environmental Protection Agency.

Kaitlin Sullivan
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Kaitlin Sullivan is a freelance health, science, and environmental journalist.