GALVESTON, TEXAS—Plans for one of the world’s biggest and most expensive flood barriers were born in a second-floor apartment here in this city on the Gulf of Mexico, as water 4 meters deep filled the street below. In September 2008, Bill Merrell, an oceanographer at Texas A&M University, Galveston, was trapped with his wife, daughter, grandson, and “two annoying chihuahuas” in the historic building he owns. Outside, 180-kilometer-per-hour winds generated by Hurricane Ike rattled windows and drove water from the gulf and Galveston Bay into the city.
As saltwater swirled through the shops and restaurants downstairs, Merrell sat in his office and sketched plans for a project he hoped would put an end to the storm-driven flooding that had repeatedly devastated this part of Texas.
It was an ambitious vision: Seventy kilometers of seawalls rising 5 meters above sea level would stretch the length of Galveston Island and beyond. Enormous gates would span the 3-kilometer-wide channel through which ships pass in and out of Galveston Bay. The defensive perimeter would seal off not just Galveston, but the whole bay, with Houston at its far end, protecting more than 6 million people and the country’s largest collection of chemical plants and oil refineries.
Though Merrell had spent decades studying ocean currents and storm surges, he had no engineering experience. But as he watched the murky waters soak the city, including his own carefully restored 19th century landmark, he decided there had to be a better way. “The Dutch would never put up with this,” he said to his wife.
Today, that first brainstorm has morphed into a $31 billion plan from the U.S. Army Corps of Engineers, the nation’s builder of mammoth water infrastructure. The state of Texas has embraced the idea, creating a taxing district to help pay its share. In July, Congress authorized the Corps to proceed—though it has yet to appropriate money for construction.
The project would be the costliest ever built by the agency. By some measures it would dwarf anything else in the world. The sea gates meant to block gulf waters from Galveston Bay would span a gap bigger than the famous pivoting Maeslant barriers that hold back the North Sea near Rotterdam, Netherlands. “Everything is bigger in Texas,” quips Bas Jonkman, a civil engineer and water-control expert at the Delft University of Technology (TU Delft).
Dutch experts like Jonkman are in high demand these days. Around the world, from New York City to Singapore, governments are planning massive seawalls and other measures to ward off the rising seas and intensifying storms expected from climate change. “A lot of countries are really thinking through now: ‘How should we defend ourselves?’” says Marc Walraven, a senior adviser on storm surge barriers to the Dutch government. In the process, each country or city is confronting similar trade-offs: between protecting people and preserving ecosystems, between technically sensible designs and aesthetically acceptable ones, between maximal protection and what’s affordable.
In Galveston, Merrell and some other scientists think the Corps hasn’t struck the right balance. Merrell warns that its plan—a scaled-down version of his original blueprint—is destined to fail, perhaps catastrophically. “It’s too weak—[the defenses] would only stand up to like a 30-year storm,” he says. “Essentially you don’t have any protection” against the more extreme storms that have already left deep scars on Galveston—and are likely, as climate change advances, to leave more.
Like a gymnast on a balance beam, Galveston perches on a slender ridge of sand, precarious and exposed. To the north, behind that barrier island, lies Galveston Bay, an estuary half the size of Rhode Island, teeming with shrimp and birds. The bay is so shallow, locals joke that if you fall out of a boat, just stand up. To the south, Galveston faces the Gulf of Mexico, whose warm waters fuel hurricanes nearly every year.
Merrell’s 1870 building in the Strand Historic District has survived a number of them, including the all-time worst. In September 1900, a monster Category 4 hurricane with gusts topping 210 kilometers per hour blasted the area. Driven by the wind, flood waters nearly 5 meters deep surged into the city from both the bay and the gulf, crushing thousands of buildings. More than 8000 people died. It’s still the deadliest natural disaster in U.S. history.
In the aftermath, local leaders and the federal government erected a 6-kilometer-long, 5-meter-high seawall along the gulf, filling the space behind it with a deep sand layer that sloped gently toward the bay. On that raised ground, they rebuilt their city.
When Hurricane Ike made landfall a century later, Galveston’s seawall held. But bay waters flooded central Galveston, including the Strand, from the less protected northern side. Low-lying neighborhoods nearby washed away. Storm surge inside Galveston Bay drenched towns dozens of kilometers from the gulf. When the water receded, it left behind $37.5 billion in damage and 74 dead.
Galveston got lucky. At the last minute, the storm veered east, sending the eye over the city and up the bay. In the Northern Hemisphere, where cyclones rotate counterclockwise, the most destructive winds blow on the eastern side, known as the “dirty side.” Sam Brody, a coastal planner at Texas A&M Galveston, calls Ike a “near miss.”
A month after the storm, in a small online newsletter, Merrell wrote a column unveiling his idea for a wall that would barricade the barrier islands and Galveston Bay during a storm. He called it the “Ike Dike.”
Although the name caught on, the idea didn’t at first. Some derided it as a monumental overreach in a place that had relied for years on more modest seawalls to protect towns like Galveston, and on perching houses on stilts. But eventually the Corps, which has a regional office on the outskirts of Galveston, agreed to study the matter. In 2021, it signed off on the current plan, which Congress authorized this summer.
The blueprint has key features in common with the original Ike Dike. At Bolivar Roads, the chief waterway joining the gulf and the bay, four swinging gates, each more than 100 meters long, would guard two openings big enough to fit some of the world’s largest freighters, including Panamax ships (see graphic). In Galveston, the existing seawall would be extended and improved to encircle much of the city. Overall, analysts at the Corps forecast that the system could reduce storm surge damage to the region by $62 billion over 50 years, or twice its estimated cost.
But the plan’s flood-stopping powers are less than what the Corps—and Merrell—first envisioned. In 2018, the agency had proposed a more conventional concrete seawall along the beaches and highways at the gulf’s edge, the length of Galveston Island and the Bolivar Peninsula, much like Merrell’s Ike Dike.
That proposal did not fare well with island residents. People living near the beaches objected that the wall would be an eyesore, even as it left many homes unprotected. “The public went ballistic,” says Kelly Burks-Copes, an ecologist who led the crafting of the plan. “We had some really harsh, really confrontational public meetings.”
Recently, standing on a 50-meter-wide beach in front of the houses that crowd Galveston Island’s gulf shore, Burks-Copes explained how the Corps adapted to the criticisms. In its final plan, the agency replaced much of the seawall with two parallel dunes built from sand dredged offshore, each roughly 2.5 meters tall. One dune would crest at 3.7 meters above sea level, and a second, farther up the sloping beach, at 4.25 meters—almost 1 meter shorter than the earlier proposed wall.
The new plan didn’t trigger an outcry from locals, but it also doesn’t offer them as much protection. The dunes are sized to withstand the kind of storm that, in the historic record, has come along every 50 years on average. The surge from a storm like Ike (which an agency engineer pegged at about an 80-year storm) would flood over the embankments, the Corps acknowledges.
But Burks-Copes said the agency will be able to blunt some of the flooding by closing the Bolivar Road gates at low tide before a big storm arrives, leaving room in the estuary for some of the overflow. Most beachfront homes, meanwhile, are now less vulnerable than when Ike arrived, Burks-Copes noted, because they’ve been elevated on pilings. “Unless the surge is over the first floor,” she said, “they’re not impacted.”
Even under its plan, the Corps estimates that damages from multiple storms over 50 years could still reach $30 billion or more in the Galveston Bay region. The agency’s estimate of how often a storm of a certain size is likely to strike is based, however, on historical patterns. It does not take into account how a warmer future might alter that equation.
Debate and uncertainty surround the many ways a warmer planet could influence tropical cyclones. But there is broad agreement that the most severe storms—such as Category 4 and 5 hurricanes—will become more intense, says Gabriel Vecchi, a Princeton University climate scientist. And an increasing number of storms in the Gulf of Mexico will be Category 3 or bigger, predicted a 2017 study by scientists at the National Center for Atmospheric Research.
The Corps has understated the risks posed by such storms, Merrell and his collaborators warn, because it overstates the protection the new dunes will offer. “I know from my own experience that those dunes will be completely obliterated by any significant hurricane,” says Bruce Ebersole, a civil engineer who until 2011 oversaw storm and flood protection research at the agency’s laboratory in Vicksburg, Mississippi.
Ebersole, who recently retired from a research position at Jackson State University, worked with Merrell to craft the Ike Dike plan and to vet the proposal from the Corps. He says agency modelers assume the dunes will act like a solid 3.5-meter wall during a storm. But in a major hurricane, “They’re going to be eroded and destroyed quite early,” he says. “Their effect on storm surge,” he suspects, will be “negligible.”
To stand up to a 100-year storm, colleagues calculated the dunes would need to be far more massive: nearly 7 meters tall with a crest 45 meters across, almost as wide as a U.S. football field. A more realistic solution, Ebersole and Merrell argue, would be building the original Ike Dike seawall, or an artificial dune made of sand spread over a hardened core of rocks or concrete.
Their view has won support from some important local political leaders, such as Michel Bechtel, mayor of Morgan’s Point, a town on the northwestern shore of Galveston Bay. Bechtel is president of the board for the Gulf Coast Protection District, which the state created to collect taxes to help pay for the project. Bechtel questions why any barrier on the islands would be built lower than the nearby Galveston city seawall and the gates spanning the water channel. “Why are we spending billions of dollars to do that and have it overtopped?” he says. “Let’s look at it with common sense.”
There is an argument for spending many billions more than the Corps has proposed on protecting Galveston Bay. It rests on a worst-case scenario that envisions hurricane-driven floodwaters battering Houston, the nation’s fourth largest city, some 80 kilometers away. Modeling by both Ebersole and Clint Dawson, who studies coastal ocean dynamics at the University of Texas, Austin, shows a Category 4 hurricane could drive a storm surge topping 7 meters into the northern tendrils of the bay, where the shore is lined with sprawling oil refineries and chemical plants.
That’s Jim Blackburn’s nightmare. Earlier this year, the veteran environmental attorney, co-director of Rice University’s Severe Storm Prediction, Education, & Evacuation from Disasters Center (SSPEED), pictured that scenario as he stood on a bluff looking across the placid waters of the bay near Buffalo Bayou. At his back, a concrete tower topped by a single enormous star marked the site of the 1836 Battle of San Jacinto, which paved the way for Texas’s independence from Mexico. Ahead, Blackburn faced an industrial landscape of metal towers and white tanks that sprouted like giant mushrooms along the waterfront. “Every one of these tanks could be hit. That’s what I’m horrified about,” he said. “This complex is incredibly vulnerable.”
About 30% of the country’s crude oil and 25% of its natural gas are processed in coastal Texas, much of it around Galveston Bay. The region’s refineries can churn out 2.5 million barrels a day, nearly 15% of the U.S. capacity. Oil is stored in more than 4600 huge tanks, many near Houston.
If a 500-year storm hit, Rice scientists have found, the surge and winds could damage some 700 tanks, spilling as much as 470 million liters of oil—almost as much as the 2010 Deepwater Horizon spill in the Gulf of Mexico, the largest in U.S. history. The waters could also inundate Houston neighborhoods kilometers upstream of the tanks. “The toxic goo that might be produced could set back not only the region, but the country, for decades,” says Houston City Council Member David Robinson, an architect who chairs the council’s infrastructure committee.
For Robinson, some version of the Ike Dike is the cornerstone of preventing that nightmare. But he worries it’s not enough. That’s because, even if the defenses succeed in reducing a storm surge originating from the gulf, a major hurricane could still generate a surge inside the bay.
Houston, surrounding Harris County, the Port of Houston, and a local entrepreneur have committed $1 million to SSPEED for studies. Blackburn and his colleagues have already touted one solution. They propose building a string of artificial islands in the bay—in effect a second wall guarding its northwestern reaches, including Houston. “The Dutch talk about multiple lines of defense,” Blackburn says. “That’s what we’re really talking about here.”
One obstacle is cost: Blackburn estimates building the islands would add $3 billion to $6 billion to the price of the plan advanced by the Corps. Another issue is the potential environmental damage caused by yet another huge engineering scheme. Regulators “are just not going to let some massive island be built in the middle of Galveston Bay,” says Bob Stokes, president of the Galveston Bay Foundation, an environmental group.
Environmental concerns have already prompted the Corps to ditch one part of the Ike Dike—a proposed gate system across the shallow San Luis Pass, a smaller channel joining the gulf to the bay’s western end. Putting a barrier there would “cause irreparable environmental impacts” by interfering with ecologically rich tidelands, Burks-Copes says.
Stokes fears that even the remaining gates on the deeper Bolivar Roads channel could meddle with tidal currents and wildlife—including commercially valuable shrimp. As a result, his group has withheld judgment on the agency’s plan. “It’s hard to say we’re for or against it,” Stokes says, “until we actually have a deeper level of environmental analysis.”
All these protection plans come an important caveat: They would do little to prevent the destruction caused by storms like 2017’s Hurricane Harvey, which brought record inland rains—not a wind-driven storm surge—that flooded Houston neighborhoods.
Other cities in the United States and elsewhere are wrestling with similar issues as they consider new defenses against storm surges. In September, the Corps issued plans for a $52 billion network of barriers in New York Harbor to fend off a repeat of 2012’s Hurricane Sandy. That option beat an earlier proposal for a single gated wall guarding the whole harbor, which earned widespread criticism in part for its $119 billion price tag. Also in September, the agency said it would reconsider its proposal to build 10 kilometers of seawalls and gates, 6 meters high in some places, around downtown Miami. Local officials and environmental groups had strongly objected to the plan, fearing it could further degrade Biscayne Bay and ruin the city’s famous shoreline.
In Singapore, officials announced plans earlier this year to study the feasibility of storm barriers. Indonesia is considering a giant sea wall to protect Jakarta, its sinking capital, even as it builds a new capital city elsewhere. In 2020, Venice, Italy, after decades of debate and delay, finally inaugurated a system of 72 mobile walls to seal off its lagoon and protect the flood-prone city from rising seas and extreme high tides. The system is working—but environmentalists say it threatens to destroy salt marshes.
Underlying many of the debates about the costs and impacts of flood barriers are deeper questions: How much risk is tolerable, and what is worth preserving? Do you build for a once-in-a-lifetime or a once-in-a-millennium storm? And how do you account for the uncertain effect climate change will have on those odds?
In the Netherlands, key coastal defenses are built to withstand freakishly rare 10,000-year storms. That partly reflects the existential threat of flooding to a nation in which one-third of the land is below sea level, including much of Rotterdam. In the United States, by contrast, the Corps frequently designs projects for a storm expected to hit once in a century.
There’s no reason different regions should adopt the same standard, says engineer Gregory Baecher of the University of Maryland, College Park, who served on a National Academy of Sciences panel in the 2010s that studied how the Corps evaluates risks. In the Netherlands, he notes, surges from a 1000-year storm aren’t much deeper than those caused by a 100-year storm, because even very rare storms there aren’t much more severe. Gulf Coast hurricanes, however, can dwarf European storms. By one estimate, the surge from a 100-year storm in the gulf is roughly equal to a once-in-a-millennium storm in the Netherlands. So, building to the more conservative Dutch-level standard along the gulf would be an enormous task. “Everybody loves the Dutch,” Baecher says. But, “They’ve got an easier problem.”
Merrell says the split also reflects a different attitude. The Dutch build to prevent flooding, whereas the United States is more willing to accept flood damage and then rebuild. But allowing another Ike-scale flood to hit the Texas coast, Merrell says, would be “insane. … We have to protect it. We can’t recover it anymore. It’s just too expensive.”
The Corps says federal law requires it to build projects that, over 50 years, will produce benefits greater than the cost. If a region wants something more robust, it must be willing to pay the higher price—but it might be a lot higher, warns agency engineer Mike Braden. “How close to 100% [protection] are we trying to get?” he asked earlier this year as he stood on the beach next to Burks-Copes. “As we try to approach that 99%, 100% solution, the costs exponentially go up.”
Braden, who arrived in Galveston earlier this year, has a title out of a Marvel superhero movie: He’s chief of the Mega Project Division at the Corps. That means he’s in charge of shepherding the Texas project through the remainder of the planning process and breaking ground. If everything goes smoothly—if Congress appropriates the money, and the project survives challenges from opponents—it will take decades to complete. The Corps now predicts the system could be finished by 2043.
Braden is open to tweaking the design. But he also hears the clock ticking. His biggest fear is that a massive storm rivaling Hurricane Ike or the 1900 disaster will arrive before the work is done. If we don’t want to repeat those catastrophes, he said, “We need to go, go, go, go.”