When Hurricane Ike made landfall in 2008, Bill Merrell took shelter on the second floor of a historic brick building in downtown Galveston, Texas, along with his wife, their daughter, their grandson, and two Chihuahuas. Sustained winds of 110 mph lashed the building. Seawater flooded the ground floor to a depth of over 8 feet. Once, in the night, Merrell caught glimpses of a near-full moon and realized they had entered the hurricane’s eye.

Years earlier, Merrell, a physical oceanographer at Texas A&M University at Galveston, had toured the gigantic Eastern Scheldt storm surge barrier, a nearly 6-mile-long bulwark that prevents North Sea storms from flooding the southern Dutch coast. As Ike roared outside, Merrell kept thinking about the barrier. “The next morning, I started sketching what I thought would look reasonable here,” he said, “and it turned out to be pretty close to what the Dutch would have done.”

These sketches were the beginning of the Ike Dike, a proposal for a coastal barrier intended to protect Galveston Bay. The core idea: combining huge gates across the main inlet into the Bay from the Gulf of Mexico, known as Bolivar Roads, with many miles of high seawalls.

Just across from Galveston, at least 15 people died that night on the Bolivar Peninsula, and the storm destroyed some 3,600 homes there. Bodies were still missing the next year when Merrell began to promote the Ike Dike, but, he said, the idea “was really ridiculed pretty universally.” Politicians disliked its costs, environmentalists worried about its impacts, and no one was convinced that it would work

Merrell persisted. Returning to the Netherlands, he visited experts at Delft University and enlisted their support. Over the next few years, Dutch and US academic researchers carried out dozens of studies on Galveston Bay options, while Merrell and his allies gathered support from local communities, business leaders, and politicians.

In 2014, the US Army Corps of Engineers partnered with the state to study Ike Dike-like alternatives for Galveston Bay. After many iterations, bills to establish a governing structure for the $26.2 billion barrier proposal, which the Corps developed alongside the Texas General Land Office, recently passed both the Texas House and Senate. In September, the Corps will deliver their recommendations to the US Congress, which will need to approve funding for the project.

No one can guess the barrier proposal’s exact fate, given its enormous price tag. And as sea levels rise and storms intensify with global climate change, Houston is far from the only US coastal metropolitan region at serious risk. Multibillion-dollar coastal megaprojects already are underway or under consideration from San Francisco to Miami to New York City.

President Joe Biden’s new $2 trillion national infrastructure initiative specifically calls for projects on the country’s embattled coasts. The initiative for Houston, the fifth-largest US metro area and the vulnerable heart of the petrochemical industry, spotlights the tough decisions for coastal megaprojects, which must balance societal needs, engineering capabilities, environmental protections, and costs.

Meanwhile, the seas keep rising. “It’s a significant tension between the need to address these issues and do it quickly,” said Carly Foster, a resilience expert at the global design consultancy Arcadis, “and also do it right.”

Lines of defense

Galveston Bay is a low, sandy subtropical estuary, bordered to the north and west by Houston’s sprawl. About twice the size of New York City, the bay is only 6 feet deep on average, with a deep channel dredged for tankers and other huge vessels traveling to and from the Port of Houston.

Given the sheer size and complexity of the Galveston Bay region, “balancing the environment and people and economics is just really tough,” said Antonia Sebastian, an assistant professor of applied hydrology and water resources at the University of North Carolina at Chapel Hill. Planners must weigh the costs and benefits, to minimize risks to an acceptable level. “And what that acceptable level is can be widely debated,” she said.

Moreover, the risks are growing. Last year, five hurricanes hit the US Gulf Coast, one with sustained winds up to 150 mph. There’s scientific consensus that climate change will cause greater numbers of these monster Atlantic hurricanes, said Ming Li, a physical oceanographer at the University of Maryland Center for Environmental Science.

As the sea rises, the land is also sinking: In the last century, the Texas coast sank about 2 feet into the sea, partly due to excessive groundwater pumping. Computer models now suggest that climate change will further lift sea levels somewhere between 1 and 6 feet over the next 50 years. Meanwhile, the Texas coastal population is projected to climb from 7 to 9 million people by 2050.

“We are absolutely going to have hurricanes hitting the Texas coast,” said Kelly Burks-Copes, an Army Corps of Engineers ecologist and project manager for the study that generated the barrier proposal. “There’s a significant barrier island system that naturally affords a defense to potential surge coming in from the Gulf, but it’s become populated over time and eroded over time. And so we are particularly vulnerable to what we call killer surges.”

Protecting Galveston Bay is no simple task. The bay is sheltered from the open ocean by two low, sandy strips of land—Galveston Island and Bolivar Peninsula—separated by the narrow passage of Bolivar Roads. When a sufficiently big storm approaches, water begins to rush through that gap and over the island and peninsula, surging into the bay.

Building on Merrell’s concept, the centerpiece of the latest Corps proposal is a massive set of gates across the Bolivar Roads. As a storm approaches, the two main navigation gates will float and swing out of dry docks to close the channel. Each will be 82 feet high—with 22 feet above water when closed—and 650 feet wide—almost twice the length of a football field. These giants will be combined with two smaller swing gates, plus a set of vertical lift gates that stay open in normal weather to let the tides flow.

The Corps also plans to raise two parallel lines of dunes, which would run 43 miles along the Bolivar Peninsula and the unprotected western side of Galveston Island, fronted by 250 feet of beach. Constructing them, the Corps estimates, will require 40 million cubic yards of sand. Additionally, since a storm on the scale of Ike would wash away the dunes and surge into the Bay, the project calls for other gates and walls around the Bay, including a ring barrier encircling the city of Galveston.

“What we are proposing is multiple lines of defense,” said Burks-Copes.

Proponents also are thinking big about environmental repair, restoring 6,600 acres of ecosystems such as wetlands, bird rookery islands, and oyster reefs, some located elsewhere along the Texas shore. “We did both coastal storm risk management and ecosystem restoration and we selected sites that actually afford a natural defense system,” choosing those “that would still provide critical ecosystem habitat,” Burks-Copes said.

The coastal barrier has earned enthusiastic support from numerous local politicians and members of Congress. “We need it yesterday,” said Houston mayor Sylvester Turner in August 2020, after Hurricane Laura struck the nearby Louisiana coast, narrowly missing the Galveston Bay.

But Merrell and other experts also raise concerns about how well the Corps plan would protect the region from the worst blows. Some environmental advocates are skeptical the environmental impacts are worth the benefits. And many observers suggest that localized projects, such as raising homes and building smaller seawalls, may offer better and quicker payoffs.

https://arstechnica.com/?p=1778005