The Great Wall of Louisiana
With the recent flooding of New York and New Jersey by hurricane Sandy it is a good time to revisit New Orleans and the work that was done by the U.S. Army Corps of Engineers to protect it from future flooding. The new system is believed to be Category 5 storm proof. A Category 5 storm has winds up to 155 mph and involves complete roof failure on many residences and industrial buildings. Some complete building failures with small utility buildings blown over or away occurs. Flooding causes major damage to lower floors of all structures near the shoreline. Massive evacuation of residential areas may be required. The areas protected include New Orleans East, metro New Orleans, the 9th Ward, and St. Bernard Parish all of which were inundated during Katrina.
Katrina, which was the costliest natural disaster in US history prior to Sandy, was a Category 5 storm over the Gulf of Mexico but weakened to Category 3 as it came ashore; the many levees that surround New Orleans were breeched in many dozens of places. Rebuilding these levees was important and over 350 miles were rebuilt bigger and stronger. But in addition it was decided that a massive new structure would encircle the city to protect it from storm surge.
NEW ORLEANS—On a sweltering blue-sky September day, I stand atop a 26-foot-tall white concrete wall that stretches for nearly two miles across the Golden Triangle Marsh on the eastern edge of the city. The $1.1 billion Inner Harbor Navigation Canal-Lake Borgne Surge Barrier is wide enough to accommodate a Ford F-250 truck and ranks as one of the biggest public works projects in the United States. Built by the U.S. Army Corps of Engineers, the wall contains a Hoover Dam’s worth of concrete. It is, as officials proudly point out, visible from outer space. In the distance I catch a glimmer of Lake Borgne, a 282-square-mile lagoon that flows into the Gulf of Mexico. When Hurricane Katrina struck New Orleans on Aug. 29, 2005, there was nothing here to stop a 15-foot-high wall of water that roared out of the lake and tore through shipping canals leading into the city, toppling levees and floodwalls and drowning the Lower Ninth Ward.
“One of the challenges you have in building anything in New Orleans—when it comes to risk reduction—is that the city depends on water,” says Ricky Boyett, public affairs chief for the Corps in New Orleans. “It’s the basis for the economy; it’s the basis for our culture. It also surrounds us on three sides.”
The Corps’ $14.5-billion solution to protect a city that sits below sea level? Go medieval.
FULL COVERAGE: Project Katrina: A Decade of Resilience in New Orleans
Today, a decade after Katrina left 80 percent of New Orleans underwater and killed more than 1,600 people, the Big Easy has been reconstructed as a walled city. The Lake Borgne Surge Barrier is just one of a series of gargantuan structures and reinforced levees and floodwalls designed to defend the city against a 100-year storm—a Katrina-like catastrophe that has a 1 percent chance of occurring in any given year. This feat of engineering, prosaically called the Hurricane and Storm Damage Risk Reduction System, forms a 133-mile enclosure around New Orleans and the 350 miles of canals that traverse the city—the canals the Corps had relied on to contain floods and that failed so disastrously in 2005. “We’re taking the fight to the storm instead of letting it come to us,” says Boyett.
Inner Harbor Navigation Canal–Lake Borgne Surge Barrier. (Map: Google Maps; photo: ASCE/Facebook; infographic: Marc Fusco)
Boston, New York City, and London are among other metropolises moving to fortify their defenses as sea levels rise and hurricanes and cyclones become more destructive. With climate change threatening coastal cities around the world, delegations of officials from Brazil to Bangladesh, China to the Czech Republic, have made the pilgrimage to New Orleans to stand on the “Great Wall” of Lake Borgne and see if Louisiana’s response to past disasters foretells their future.
After Katrina, the Corps ran data from 152 hurricanes through computer models thousands of times to design a system that could withstand a 100-year storm in 2057. But there’s a wild card: The once vast wetlands that buffered New Orleans from Mother Nature’s wrath are disappearing at an accelerating clip. Will these billion-dollar walls hold as the Gulf of Mexico advances toward the city? Or will New Orleans become the American Atlantis, slowly sinking beneath the waves?
The Great Wall of New Orleans
New Orleans’ unique geography—about half the city sits in a bowl and is between three and 12 feet below sea level—has long forced residents to rely on elaborate fortifications to hold at bay the water that surrounds them. That dependence has only grown as marshes and swamps that naturally help contain storm surge have been lost to industrial development and the very flood prevention measures meant to protect the city. A mile of cypress swamp, for instance, can reduce storm surge by a foot, according to the Corps. Over the past 80 years, though, 1,900 square miles of wetlands—that’s about the size of Delaware—have been destroyed as levees built to keep the Mississippi River from flooding the city have choked off the supply of sediment that replenishes marshes and swamps. The oil and gas industry, the lifeblood of Louisiana’s economy, has eliminated untold acres of wetlands by extending an ever-growing infrastructure of canals and pipelines into the bayous. Today, a football field–size patch of Louisiana wetlands disappears every hour. Within 50 years, another 1,750 square of miles of wetlands could be submerged.
Inner Harbor Navigation Canal–Lake Borgne Surge Barrier under construction in 2010. (Photo: Wikipedia)
While New Orleans has built the world’s most expensive flood control system in the space of a few years, it will take decades to restore a faction of the lost wetlands under a $50 billion state plan that seeks to reclaim 580 to 800 square miles of marsh in 50 years. New Orleans also has developed a proposal for a “living water system” to reduce reliance on pumping and canals. It would do that by using parks, urban wetlands, and other natural features to store and absorb rainwater within the city.
“The first line of defense is your barrier islands, your wetlands, your marshes, your good solid bottomland hardwoods,” says Boyett. “You’re starting to see marsh creation programs, and we’re using sediment from the Mississippi River to reinforce barrier islands. But we’re never going to reclaim everything that has been lost—it simply can’t be done.”
Which means New Orleanians’ survival today hinges on structures like the IHNC Lake Borgne Surge Barrier. The great white wall stretches across the Mississippi River–Gulf Outlet and the Gulf Intracoastal Waterway—two canals that flank the Golden Triangle Marsh and that funneled the Katrina storm surge into New Orleans. The surge barrier connects to 32-foot-high floodwalls on either side of the structure that wrap around the eastern and southern ends of the city.
Castle-like construction of the Inner Harbor Navigation Canal–Lake Borgne
Surge Barrier. (Photo: Courtesy U.S. Army Corps of Engineers/Flickr)
The top of the barrier sports crenellations reminiscent of the battlements atop a medieval castle. They serve a similar purpose.
“When you have a surge going over the top, it helps disperse the impact,” says Chris Gilmore, a senior project manager with the Corps, standing near massive 150-foot-long pie-shaped yellow gates as a cargo ship slowly passed through the opening, one of three along the barrier. “Barge gates take all day to close. As soon as we have an indication that a storm is coming in 96 hours, we’ll close it down.”
The idea is to seal off the city far from the storm surge. “When a storm is coming through into New Orleans,” says Boyett, “one of the things we want to do is we want to block that storm at the perimeter. And by blocking the surge off, we’re able to keep the water from getting into the interior of the city.”
Going Dutch
When Katrina struck, New Orleans was essentially defenseless on its southern flank west of the Mississippi River.
“We had enormous holes in our system,” says Susan Maclay, president of the Southeast Louisiana Flood Protection Authority–West, which is responsible for Jefferson and Orleans parishes on the west bank of the Mississippi. “So we were very fortunate the storm was not positioned differently, or 250,000 people over here would have looked like the Lower Ninth Ward over there.”
Maclay speaks as she stands inside the noisy pump house of a new $1.2 billion structure called the West Closure Complex, which is designed to repel a meteorological assault on the city from the south. A 480-foot-long, eight-story-high pumping station and 225-foot-long orange floodgates stretch across the Gulf Intracoastal Waterway, the New Orleans skyline shimmering in the humid haze miles away.
(Map: Google Maps; photo: Courtesy U.S. Army Corps of Engineers; infographic: Marc Fusco)
If a hurricane hits, the barrier holds back the storm surge charging up the intracoastal waterway from the Gulf of Mexico. The canals on the city side of the structure drain the downpour falling on this part of New Orleans. Eleven huge pumps keep those canals from flooding the city, pumping water at a rate of 8.5 million gallons a minute back into the intracoastal waterway.
“We come closest to mimicking what the Dutch have,” says Maclay, referring to the’ elaborate flood control system keeping the Netherlands, which is below-sea-level, above water.
A Tragic Mistake
There was nothing to stop the wall of water 10 to 13 feet tall that rose out of Lake Pontchartrain on the city’s heavily populated north side on the morning of Aug. 29, 2005. The surge swept into the three canals that were supposed to carry water out of the city during a storm. The levees broke and poorly constructed floodwalls lining the canals folded, inundating the surrounding below-sea-level neighborhoods. With the walls down, other parts of New Orleans began to flood when pumping stations could no longer send water into the destroyed drainage canals.
Today, 11-ton steel gates drop into place to seal off the three canals from the lake when a hurricane approaches. Banks of temporary pumps quickly installed after Katrina send water around the gates and back into the lake. At the 17th Street Canal, construction continues on permanent pumps capable of pumping nearly 90,000 gallons of water a second.
(Map: Google Maps; photos: Mary Grace McKernan; infographic: Marc Fusco)
In New Orleans’ Fillmore Gardens neighborhood, new floodwalls sit on new levees along the London Avenue Canal. The Corps is reinforcing the levees—a process called “armoring” —so that even if a storm surge overtops the floodwalls, they will not fall. But there is little left to protect in some parts of this neighborhood. When the wall directly behind a house at 5000 Warrington Dr. collapsed on Aug. 29, 2005, the force of the water spun the yellow-brick home 180 degrees and pushed it 100 feet down the street until it slammed against four oak trees. Now, a few new houses, some sporting solar panels and standing eight feet off the ground, are scattered among scores of empty green lawns where homes once stood.
In the years after Katrina, investigations revealed that the Army Corps of Engineers failed to drive floodwall pilings deep enough into the levees to withstand the water pressure as the surge sped out of the lake and into the canals.
The failing floodwalls of the Inner Harbor Navigation Canal were directly responsible for the flooding of the Lower Ninth Ward and Bywater neighborhoods during Hurricane Katrina. (Map: Google Maps; photo: Mary Grace McKernan; infographic: Marc Fusco)
“I watched them drive the sheet pilings, and they were short,” says Kenneth Evans as he stands on a deserted street yards from the rebuilt floodwall. After Katrina, his mother was one of the few residents to return to the neighborhood where he grew up. “You could see it. We were hoping and praying they’d hold,” Evans says, “and they didn’t.”
“A lot of people drowned right around here,” he adds quietly. “See all this empty space? We had neighbors all the way to my house. As you can see, nobody came back because their houses were totally destroyed.
Sandy Rosenthal is the executive director of Levees.org, a citizen watchdog group formed after the hurricane. “When these canal walls were built, we were doomed,” she says, standing alongside Evans. “They were guaranteed to fail. It was a tragic mistake.”
“Those structures that you saw?” she continues, referring to the surge barrier and the West Closure Facility. “If we had anything like that before Katrina, this wouldn’t have happened. We’re safe now.”
Perhaps. But Boyett of the Corps warns New Orleanians against letting down their guard. Bigger storms than Katrina inevitably will strike, and the city’s reliance on engineering ingenuity could well fail, as it did a decade ago. “We urge people not to be complacent,” he says a few weeks before the 10th anniversary of Katrina. “Please listen. And evacuate.”
The Great Wall of Louisiana
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