On August 29, 2005, Hurricane Katrina drowned New Orleans and notably town’s low-income Decrease Ninth Ward. The flooding killed virtually 1,400 individuals. The levees and floodwalls, primarily constructed by the U.S. Military Corps of Engineers, failed to carry again the hurricane’s storm surge of seawater. Just some days after the storm raged, President George W. Bush stated, “I don’t assume anyone anticipated the breach of the levees,” as media retailers confirmed survivors stranded on freeway overpasses or stuffed into town’s Superdome in putrid circumstances.
However in 2001, simply 4 years earlier than the hurricane, scientists and engineers throughout Louisiana had predicted precisely what would unfold. They’d proven how storm surge would swell and overwhelm town’s insufficient defenses. I used to be with these scientists on the time and defined their predictions in a Scientific American article, however governments took virtually no motion on the enhancements the scientists advisable.
In true American style, the U.S. ignored a solvable drawback till catastrophe struck.
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Instantly after the disaster, politicians in any respect ranges made grand statements about what wanted to be executed to raised defend town and coast. Two months after the tragedy I went again to battered southeastern Louisiana to see what the scientists, engineers and concrete planners thought as an alternative. In early 2006 Scientific American printed an article mapping out three potential situations. Louisiana later issued its Coastal Grasp Plan (CMP) to place a bunch of enhancements in place, which aligned with a few of what I had reported, together with, for instance, a hoop of upgraded defenses proper across the metropolis.
Since then state officers have up to date the plan, most lately in 2023, and they’re engaged on the following iteration for 2029. The query in the present day is whether or not New Orleans is best protected in opposition to hurricanes than it was 20 years in the past. The quick reply is that town itself has better defenses—for now. Levees have been raised, floodwalls have been rebuilt utilizing a lot sturdier designs, and large gates have been constructed to cease not less than some sea surge from ramming instantly into town when a storm is approaching.
However exterior town, some locations is probably not safer. Others could even should be deserted. The huge marshland south, west and east of town supplies pure safety in opposition to lethal storm surges, however it’s deteriorating, and as that continues, New Orleans will probably be extra instantly uncovered to indignant seas. But in July Louisiana officers canceled a keystone challenge that may have helped restore these wetlands.
All the time, effort and cash that has gone into defending the state’s most populous metropolis might now be in danger.
New Orleans lies in a bowl that’s virtually all under sea stage. The land has been sinking for many years and continues to drop. The big Lake Pontchartrain, at sea stage, looms on its northern facet. The Mississippi River, additionally at sea stage, runs alongside town’s western and southern facet, then turns south by means of many sq. miles of marshlands and empties into the Gulf of Mexico. Like many massive rivers, the Mississippi floods throughout the spring and sometimes at different occasions. In southeastern Louisiana, the floods used to spill over pure banks and produce sediment, freshwater and vitamins to the wetlands—assets that preserve vegetation thriving, counteract pure subsidence, and change sediment that routine wave motion and storms are inclined to scour away.
However individuals don’t see floods for the nice they supply, simply the houses they destroy and the people they wash away. Louisiana’s municipalities and the corps constructed floodwalls alongside the various navigation channels that crisscross town to maintain water out of neighborhoods and business districts that lie under within the bowl. And for a century, the corps constructed levees—excessive, lengthy mounds of earth, concrete and rock—alongside all the size of the Mississippi, on each banks, north and south of New Orleans. Floods into town stopped, however the lack of floods starved the wetlands of their lifeline. The thick mesh of vegetation started to die. The deterioration is so dangerous that southern Louisiana is shedding an acre of land—the scale of a soccer subject—each 100 minutes.*
After all it’s not potential now to take away sections of levees and partitions as a result of floods would spoil the municipal and industrial complexes people have constructed there. The intensive community of canals and pumps that every day ship easy rainwater and groundwater that collects within the bowl out to the lake might by no means sustain. In June the SwissRe Institute, which analyzes the insurance coverage trade, reported {that a} repeat of Hurricane Katrina in the present day would value the trade almost $100 billion—though town’s inhabitants stays 20 % under what it was in 2005, when individuals fled or later moved away.
Because the CMP was first issued, New Orleans and the state have spent $14 billion to enhance storm safety. They’ve constructed storm surge limitations and floodgates alongside town’s perimeter to carry again excessive ocean water. They’ve raised levees that had been too low to cease surges from massive storms, armored levees that had been tender, added extra water pumping capability and stuffed gaps between sections of levees that encompass town and fast outlying areas. “There have been quite a lot of gaps that had been accomplished” within the Hurricane and Storm Injury Threat Discount System, additionally recognized merely because the ring system, says Bradley Barth, operations chief on the state’s Coastal Safety and Restoration Authority.
The state has additionally broadened barrier islands, a line of lengthy, skinny, low islands within the gulf that rim the southern edges of the wetlands. Like velocity bumps, barrier islands can minimize down storm surges which can be coming from the gulf and heading towards land, however in addition they may be worn away by these storms and common wave motion.
Beefier barrier islands, and a stronger ring across the metropolis, imply New Orleans ought to fare higher throughout giant storms. Certainly, state officers say the defenses held effectively in opposition to Hurricane Isaac in 2012 and Hurricane Ida in 2021. “The system carried out as anticipated,” Barth says.
But scientists and engineers are involved that the intensive wetlands between town’s perimeter and the coast’s edge, which proceed to disintegrate badly, will permit future storm surges to march in unimpeded. The rule of thumb is that each 4 miles of wholesome marsh can take up sufficient water to knock down a storm surge by one foot. The surge throughout Katrina peaked at 25 to twenty-eight ft in sure locations.
The first strategy to restore wetlands, within the CMP and different analyses, it to construct what are referred to as diversions. River flooding provides sediment that raises the wetland ground. The floods additionally present freshwater, which lowers the salinity of saltwater that naturally washes in, retaining the various vegetation knit in a soggy however strong cloth that resists erosion. A diversion is a brief opening that’s minimize within the levee. Cuts can be made alongside the south facet of the Mississippi River, which faces the wetlands that reach to the open gulf. Gates can be put in throughout the cuts in order that a lot of the yr, the river would run as regular. However throughout the spring or different occasions of excessive water, engineers would open the gates and let the sediment-rich freshwater stream into the wetlands, offering important sustenance. The CMP identifies quite a few desired diversions.
In July, nevertheless, the state canceled the biggest challenge, referred to as the Mid-Barataria Sediment Diversion, though scientists had studied the plan for years, fashions and designs had been accomplished, permits had been granted and development had begun. The work was additionally typically funded from the Deepwater Horizon Oil Spill Belief that oil and gasoline big BP had established to settle claims for damages when the Deepwater Horizon oil rig exploded off the Louisiana coast in 2010, creating the biggest marine oil spill in U.S. historical past.
“They’d began development again in August 2023, then the state simply halted it,” says Alisha Renfro, a senior supervisor on the Nationwide Wildlife Federation, who has studied coastal Louisiana for 20 years. The group advocates for coastal restoration and tries to verify the newest science is utilized in any plans. The mid-Barataria cancelation “comes as an actual disappointment,” Renfro says. “It was a long-term, large-scale resolution to restoring coastal wetlands.”
Restoration teams comparable to Restore the Mississippi River Delta roundly criticized the choice as a politically motivated cash seize. However Gordon Dove, who in 2024 was appointed by Governor Jeff Landry as chair of the state’s Coastal Safety and Restoration Authority, defended the choice. Writing in an August 15, 2025, visitor column within the Occasions Picayune, Dove stated the choice was made by the Landry administration, the U.S. Military Corps of Engineers and the Trustee Implementation Group to terminate the challenge as a result of it “aimed to deal with coastal erosion in a restricted space” and since preliminary value estimates had been rising considerably and will detract from different restoration efforts. Barth informed me the authority would “look to repurpose the cash to shoreline safety and smaller diversions.”
Renfro says the transfer is confounding and that it appears like a throwback to the times instantly after Hurricane Katrina, when competing self-interests had been arguing over what to do and fund. The state, she says, is stepping away from coordinated work and slipping again into “random acts of restoration” that would offer poorer safety total.
It doesn’t matter what officers do, New Orleans will proceed to sink. The ocean stage will proceed to rise. Local weather change will proceed to make storms stronger and rainfall heavier. Regardless of stouter levees, floodwalls and barrier islands, vibrant wetlands are essential to long-term safety, and the 2023 CMP depends on them. However 20 years after catastrophe, maybe the tough classes of Katrina are fading and politics are resurging. As this yr’s hurricane season performs out, Louisiana should bear in mind the ability of water. It should bear in mind the injury Katrina brought about, the lives it took and the price of rebuilding, which continues to be happening. Above all else, Louisiana’s energy brokers should hearken to science. The price of not doing so is throughout them.
That is an opinion and evaluation article, and the views expressed by the creator or authors should not essentially these of Scientific American.
*Editor’s Notice (8/28/25): This sentence was edited after posting to raised make clear that southern Louisiana is shedding land equal to the scale of a soccer subject each 100 minutes.
