Expect to pay at least $400 billion over next 20 years to protect U.S. from rising seas, study warns

Protecting our coastlines will cost almost as much as it did to build the interstate highway system -- but needs to be done in half the time.

'Modest' sea level rise will cost the US $400 billion over next two decades
'Modest' sea level rise will cost the US $400 billion over next two decades, new study shows. (Photo credit: Getty.)

It is going to cost the United States at least $400 billion over the next 20 years to protect the nation’s public infrastructure — everything from roads and rail lines to bridges, airports, and sewage treatment systems — to withstand the impacts of sea level rise.

That’s the finding of a new report out Thursday which looks at the cost of moderate sea level rise along the contiguous United States. The price tag is almost as much as it took to build the original interstate highway system, which cost $114 billion at the time ($521 billion when accounting for inflation) over 36 years and now spans over 48,000 miles.

In comparison, the report by Resilient Analytics and the Center for Climate Integrity states that to prepare for sea level rise, more than 50,000 miles of coastal barriers, or seawalls, will need to be constructed along 22 states. Moreover, all of this vital work would need to be done in half the amount of time it took to build the nation’s highway system.

“There is a fiscal tidal wave building along America’s coast and this study gives us a measure of its magnitude,” Skip Stiles, executive director of Wetlands Watch in Norfolk, Virginia, said during a press call.


And while climate change requires one of the “most dramatic social and economic transformations,” according to Richard Wiles, executive director for the Center for Climate Integrity, he notes that “no one has bothered to estimate what the core adaptation measures will cost.” The study hopes to change this.

According to the United Nations’ Intergovernmental Panel on Climate Change (IPCC) global sea level rise is expected to increase by 11-24 inches by 2100 under a scenario where the world limits global warming to 2 degrees Celsius above pre-industrial levels — a “modest” scenario, according to Thursday’s report.

Based on current global actions, however, scientists — including those who produced this latest report — indicate that the “more plausible” path forward is warming of anywhere between 2.6 and 6.1 degrees Celsius above pre-industrial temperatures. This would result in sea level rise of between 15 to 39 inches by the end of the century.

Thursday’s report chose to focus on the most conservative 2 degrees scenario — one that requires urgent and immediate action by all nations to curb greenhouse gas emissions — in order to focus the discussion not on worst case scenarios but rather the “baseline costs that will be required to protect our coastal communities against unavoidable, short-term sea-level rise.”

In other words, it’s all but guaranteed the world will face 2 degrees of warming and so that’s the starting point governments should use for adaptation planning.


“We purposefully analyzed more moderate and immediate scenarios to direct the policy discussion toward decisions that need to be made right now,” the report states. These are costs and choices “that cannot be avoided.”

The study breaks down the costs across states and right down to the county level. The most vulnerable state is Florida, which would, according to the report’s cost estimates, need to spend more than $75.8 billion and construct some 9,200 miles of seawall by 2040 — this would rise to $109 billion and over 12,700 miles by 2100.

Florida is followed by Louisiana, North Carolina, Virginia, and Maryland for the top five states which will need to spend the most money to protect their public infrastructure from sea level rise of up to two feet and be able to endure common, every-year flooding events. This is opposed to intense, one-in-100 year storm surges which experts recommend communities prepare for as well. Hurricane Sandy — a storm of the size experts say only occurs once every 103 to 260 years — hit New York in 2012 with a 13 foot storm surge. As climate change continues to warm the atmosphere, these types of storms will become more common.

The study uses the cost of constructing seawalls as a “consistent measure” that can be applied across the country to give an idea of how risks to various states and counties compare. And while a seawall might not be the best solution for every place, the number of miles of wall required for each area, as identified by the study, represents the number of miles that will need protection, in one form or another — all of which entail high costs.

The total number of miles indicated are not limited to pure coastline. Rather, the measurement also accounts for places further in-land that will experience sea level rise-related fooding events. These places have roads, schools, or properties that are at risk of inundation, said Paul Chinowsky, director of the environmental design program at University of Colorado Boulder and the lead scientist for the study. “Every one of those miles must have a decision as to whether it’s going to be protected,” he said, “or something is going to get sacrificed.”

The issue, however, said Stiles, is “where do we find the money?”

The study calls for polluters to pay their fair share for these protection and adaptation measures, otherwise taxpayers will be on the hook for all of these costs. With constant federal deficits, said Stiles, “the era of grand national projects [like the interstate highway] is ending.”


“There is no free lunch in coastal climate adaptation and retreat,” said Wiles, “and as it stands taxpayers are on the hook to pay the costs.”

Meanwhile, he added, oil companies continue to profit from selling fossil fuels, the primary cause of climate change, all while arguing they shouldn’t be on the hook for the damages.