It has been 20 years since New Orleans’ faulty levee system failed during Hurricane Katrina, causing a flood that claimed almost 2,000 lives and inflicted more than $150 billion in economic damage. The catastrophe was so bad that some doubted the city could continue to exist at all — the U.S. Speaker of the House at the time declared that rebuilding New Orleans “doesn’t make sense” and that much of it “could be bulldozed.”
Rather than just patch up the damage, which would have left one of the country’s most iconic cities exposed to every future storm, the federal government doubled down on flood protection, building a new $14.4 billion levee system that ranks as one of the most sophisticated anywhere in the world.
Over the course of a decade, the Corps rebuilt and expanded almost 200 miles of levees across three parishes. It outfitted every major channel and canal with a gate that could swing shut during surge events. On the east side of the city, where storm surge had overtopped its old levees, it built the Lake Borgne Surge Barrier, a two-mile wall that could stop as much as 26 feet of surge. On the three canals where it had built shoddy flood walls, it built new ones and massive pump stations that can remove an Olympic-sized swimming pool of water from the city every 3.5 seconds. It also decommissioned the Mississippi River-Gulf Outlet, or “Mr. Go,” a large shipping channel that had destroyed protective marshland around New Orleans and funneled Katrina’s storm surge into the city.
But for all the success of the new levee system, the future of New Orleans remains uncertain.
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The sea levels around the city are rising by about half an inch every year as climate change warms the oceans and melts glaciers. The city itself is sinking even faster than that, with some sections of the levee system settling by almost 2 inches each year — faster than the rate of change that the Corps projected when it built the system. This elevation change makes the new levee system less effective with each year, requiring constant repairs and expansions.
Even landmark structures like the Lake Borgne barrier may lose a few feet off their protection capacity by the middle of the century. That would put them within a hair’s breadth of being topped by storms such as Hurricane Michael, which delivered almost 20 feet of surge to Florida in 2018.
“Since 2005, several storms have made landfall on the Gulf Coast that far exceed the stated design capacity of the new ‘risk reduction system,’” said Andy Horowitz, a historian at the University of Connecticut and the author of a book on Katrina. “It’s just chance, or luck, that one of them didn’t hit New Orleans. One day, inevitably, one will.”
The Corps maintains that the system is working as designed, but federal and state cuts could jeopardize the system’s resilience even further. The Trump administration has already eliminated funding at the Corps and Federal Emergency Management Agency, or FEMA, for key resilience projects and levee inspections. Republican-controlled Louisiana is following suit. Protecting New Orleans through the end of the century, against climate-fueled hurricanes, will require the exact whole-of-government effort that the Trump administration is trying to end.
“The system that we have is a good system,” said Sandy Rosenthal, a citizen activist and the founder of the website Levees.org. Rosenthal was responsible for exposing the Corps’s original design errors after Katrina. “But for the first time since the levees were completed, I’m actually concerned.”
New Orleans has been an engineered city for centuries. Subsidence and wetland loss have driven the city to sink below sea level, turning it into a kind of bowl between the Mississippi River and Lake Pontchartrain. Even the French settlers of the early 18th century had to use levees to keep the city from flooding. Almost the entire perimeter of New Orleans is now lined with either earthen levees or concrete walls. When it rains, pumps carry water up and out of the bowl, the same way you would bail out a canoe.
This levee system has had many iterations, but the one that existed at the time of Hurricane Katrina was the federal government’s project. The U.S. Army Corps of Engineers, which is the nation’s flood protection agency, had built around 125 miles of barricades around the city over the second half of the 20th century.
The best way to describe this system is the old Woody Allen quip about restaurants — “the food here is terrible, and the portions are too small.” The Corps made serious engineering mistakes when it built flood walls along canals that funnel water away from the city’s densest neighborhoods. But even the levees it built “correctly” in the eastern part of the city, closest to the Gulf of Mexico, were too small. In other parts, there were no defenses at all.
When Katrina sent storm surge barreling toward New Orleans, the old system failed in at least six different places. The wall of water rushed over the tops of the levees, and the canals that were supposed to channel water out of the city shattered, flooding neighborhoods with water and silt. FEMA bungled the emergency response and took several days to deliver critical supplies, turning the disaster into a true humanitarian crisis.
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Katrina itself was not all that powerful, especially compared to the Category 5 monsters that now strike the Gulf in most years, but it exposed every engineering flaw in the Corps’s structure. The American Society of Civil Engineers called it the “the worst engineering catastrophe in U.S. history.”
Despite some initial skepticism about the cost of the rebuild, the federal government’s response was to throw money at the problem. In the decade after Katrina, Congress allocated more than $14 billion to the Corps of Engineers to protect the whole city against a hypothetical 100-year storm, or one that has a 1 percent chance of happening in a given year. It was classified as a repair project, rather than new construction, which meant the feds picked up the entire tab.
The new “Hurricane and Storm Damage Risk Reduction System,” or HSDRRS, comprises a network of hundreds of discrete projects touching every corner of the city. It no longer purports to offer “hurricane protection,” as the previous system did, but rather “risk reduction.”
“The new system that’s in place now is the first time New Orleans has ever had a complete approach to dealing with water,” said Ed Link, a civil engineer at the University of Maryland. Link helped lead the government-appointed task force that evaluated the Katrina levee failures. “The old system was not a system, we called it a ‘system in name only.’”
The Corps completed the major pieces by 2012 and finished its final work by 2018, a remarkable turnaround time for an agency that often spends two or three decades on major capital projects. The system passed its earliest tests: New Orleans took 9 feet of storm surge from Hurricane Isaac in 2012 and took another direct hit from Category 5 Hurricane Ida in 2021. In all these storms, things worked the way they were supposed to: The storm surge barriers kept out the Gulf of Mexico, and the pump stations stopped rainwater from flooding the city. Rosenthal said Ida showed that the system “passed the ultimate test.”
Whether it will always pass that test is another question. The federal government no longer maintains the system; that job is now the responsibility of the Southeast Louisiana Flood Protection Authority.
Though now in local hands, the authority still relies on the Corps for levee inspection funding. The Trump administration has already cut its budget, with Republicans in Congress proposing even further reductions. The Corps said it doesn’t have the money to inspect New Orleans’ levees this year or next. Much of the system’s maintenance funding also comes from local governments, some of which have chafed at the cost of keeping the levees at the Corps’s standards after Katrina.
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Louisiana’s new Republican governor, Jeff Landry, has also attempted to take control of the Southeast Louisiana Flood Protection Authority this year, giving himself more influence over what had been an independent board and slashing funding for line items like cutting levee grass. His moves to undo post-Katrina governance reforms caused three members to resign in March. Landry has selected a new board chair, fired that chair, and installed a new chair through what critics say may be illegal means.
If that wasn’t enough, New Orleans is still sinking. The city pumps its drinking water from underground aquifers, and levees farther up the Mississippi River have blocked the sediment that once replenished the delta on which the city sits. In addition, the Gulf of Mexico itself is rising by a few millimeters a year due to global warming. With these two factors combined, the relative sea level rise in Louisiana is higher than almost anywhere in the world.
The Corps was aware of climate change when it built the new system, but it was planning for a moving target. Congress gave the agency enough money to build a flood network that would protect against a “hundred-year flood” event, but the height required to protect against such an event changes each year as land subsides and the Gulf of Mexico rises. Because these rates are very hard to predict, and may be accelerating, the Corps has to inspect the levees at regular intervals and elevate the ones that are sinking fastest.
“The 100-year criteria is no longer a valid way to design things, primarily because it changes all around now,” said Link. “We added a certain amount of subsidence and a certain amount of sea level rise to our calculations, but we didn’t put enough.”
Corps spokesperson Ricky Boyett said the agency is confident that the system will provide 100-year protection through 2057, provided it has the money to lift up the earthen levees every few years. It also said it is preparing to expand the system west toward Baton Rouge and studying how to extend that 100-year level of protection for New Orleans through at least 2073, even with further subsidence.
“The goal is always to stay ahead of it,” said Boyett. The major concrete structures, like the surge barrier, were built with enough spare height to last through 2057, but only if sea levels rise as the Corps predicted — and new research from Tulane University suggests that these structures are sinking too.
The Corps also readily admits that bigger storms are possible. The HSDRRS would reduce the damage from these storms, but would not stop them altogether. As for whether it will ever build a 200-year or 500-year system, one that would be robust enough to stop supersized storms such as Hurricane Ian or Hurricane Michael, the Corps can offer no guarantees. Such funding would depend on Congress, which tends to act after big disasters rather than before them.
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Another problem is that levees are only supposed to be one part of a broader approach to resilience, and the federal and state governments are now neglecting the other parts of that approach. Landry, the Louisiana governor, just scrapped a $3 billion sediment diversion project that would have created 30,000 acres of new hurricane-slowing wetlands, bowing to pressure from a vocal group of oyster fishermen. The city, meanwhile, has pursued a novel project to slow down subsidence by capturing rainwater, but that project depends on funding from federal resilience programs that Trump is trying to cut.
“I’m not minimizing the importance of the hard levees and the other structures, but the natural stuff is as important, if not more important,” said Charles Allen, a New Orleans activist who founded an organization to support the flooded Lower Ninth Ward after Katrina. He now serves as the Gulf Coast community engagement director at the National Audubon Society. “We can’t just throw up something, turn our back, and say, ‘Oh, it’s gonna be fine.’…Now two decades have passed, and we are still fiddling.”
In the meantime, the hard levees are all New Orleans has.
Massive civil works projects like the HSDRRS may soon look like the product of a bygone era. The second Trump administration has purged the federal civil service and called for drastic reductions to government spending, and has said he wants the states to take on a greater share of disaster preparedness costs. If that model continues past his presidency, it might threaten the Corps model of proposing large capital projects that depend on money from Congress, the projects that can extend a city’s probable lifespan by a century or more.
While the new system isn’t perfect, it does demonstrate what the government can do if it tries, says Horowitz.
“I used to think of the post-Katrina ‘risk reduction system’…as the bare minimum, but subsequent events have reminded me that of course Congress could have done less,” he said. “It could have done nothing, which has been its response to many crises since. It could even engage in action that makes matters worse.”