The Next Big One

10 years after Katrina

The next Big One

New Orleans has built the infrastructure to protect itself from hurricanes, but can it win the battle against rising seas?

10 years after Katrina

The next Big One

New Orleans has built the infrastructure to protect itself from hurricanes, but can it win the battle against rising seas?

Published on August 21, 2015


Here at the bottom of the Mississippi River, Andy Nyman stands atop a squishy new wetland, recently created by sediment that may have originated hundreds of miles upstream.

“This is Ohio,” says the Louisiana State University ecologist as he sifts through a core of marsh soil, his legs shin-deep in fresh water. “This is Missouri.”

Nyman is standing in the Sawdust Bend Bayou, which was once a shallow lake. But about 30 years ago the state cut a gap, also known as a diversion, in one of the Mississippi’s banks, allowing sediment-rich fresh water to flow in and laying the groundwork for a wetland to grow. Now, black willow trees sprout from some of the fledgling land, precisely the kind of tough vegetation that could help protect the city some 95 miles upriver — New Orleans — whose vulnerability was laid bare 10 years ago.

Louisiana State University ecologist Andy Nyman examines a wetlands area in Louisiana's Sawdust Bend Bayou, about 95 miles downriver from New Orleans. A Mississippi River diversion -- a gap in the river's banks -- built in the 1980s in nearby Pass a Loutre allowed sediment-rich fresh water to flow in, helping wetlands grow in an area that was once a shallow lake. (Whitney Shefte/The Washington Post).

Today, a decade after Hurricane Katrina, the city is thriving, reassured by a new $14.5 billion complex of sea walls, levees, pump stations and outfall canals. But in the long term, New Orleans’s safety depends on far more than walls.

Louisiana has roughly 5,700 square miles of wetlands. If it keeps losing them at the current rate — estimated at a football field an hour — New Orleans could someday lie right up against the Gulf of Mexico, more exposed than ever to another natural disaster. And Nyman and many other coastal scientists say that wetland-building river diversions like the one at Pass a Loutre — only much bigger and much closer to the city — are critical to staving off that fate.

This is New Orleans’s big post-Katrina problem: ensuring the long-term viability of a city, half of which is below sea level, in a world of rising oceans. It is an issue that goes beyond simply defending against hurricanes, which is why experts are pointing to wetlands as crucial to the city’s future. Not only can wetlands weaken storm surges, they also can partly keep pace with rising seas as they accumulate sediment and plant matter.

“The greatest existential threat . . . to the city of New Orleans is the rapidity with which the coast is disappearing,” says Mayor Mitch Landrieu (D). “And if that’s not reversed, then the future of the city will be at risk within the next 100 years.”

But restoring the wetlands has been much tougher than building new hurricane protections. Despite an ambitious, $50 billion coastal “master plan” released by the state in 2012, wetland restoration has been bogged down by funding difficulties and lengthy technocratic assessments. Meanwhile, the coastal plan’s crucial river diversions, designed to restore the natural delta-building process of the river, are meeting with growing resistance from Louisiana’s coastal fishermen, who charge that the gigantic freshwater flows will drive shrimp and oysters farther away.

“We feel that’s going to kill the industry that we make a living out of,” says Brad Robin, a St. Bernard Parish oyster farmer whose boats arrive each day at the town of Yscloskey, which was devastated by a nearly 20-foot storm surge in Katrina. “It’s going to wipe this town out.”

The fishermen do not have a lot of political power. But while the river diversions wend their way through a complex scientific and technical decision-making process, opponents are gathering allies.

Two coastal Louisiana parishes, St. Bernard and Plaquemines, have adopted resolutions opposing the diversions. St. Bernard Parish’s council, which says it is “adamantly” against them, wants further studies of the diversions’ socioeconomic impact and has asked state representatives to block their funding until that happens.

Coastal scientists do not deny that the impact of the diversions on some fishing communities could be devastating. It’s just that they see so much more at stake — literally, a mega-battle against the sea. “If we do nothing, then New Orleans is still going to exist, but it’s going to be an island, or maybe a peninsula, sticking out into open water,” says Torbjorn Tornqvist, a geologist at Tulane University in New Orleans and a supporter of the diversions.

Land-building plan lets the river do the work

Part of Louisiana’s coastal restoration plan is to allow the Mississippi River to rebuild land the way it would naturally, but in a controlled way. Before the 1930s, the river added about three-quarters of a square mile to Louisiana each year by dropping sand and silt. The swamps and marshes it formed served as natural storm-surge barriers. Since levees and other structures were built to constrain the river, however, the state has lost almost 2,000 square miles of coast. The state has proposed sediment diversion keycontrolled sediment diversions, eight of them in the southeast, where new gates in levees would general flow keyallow water and sediment to flow through to build up wetland areas.

sediment map sediment map small screen

A sediment diversion in action

This is an example of a small diversion that was cut a decade ago into South Pass to restore wetlands in part of Sawdust Bend Bayou. The diversions proposed in the coastal plan would be much larger and controlled by gates.

This portion of the bayou, a marshy wetland area that was rapidly disappearing, had been chosen as part of a federally funded, state-managed project that aimed to restore 1,500 acres to the bayou. (Image: U.S. Geological Survey via Google Earth)

By the time this hole was cut through the riverbank, Hurricane Katrina had completely wiped out the land on the right. (The dark swirl in this image is fresh river water entering the murky bayou.) (Image: U.S. Geological Survey via Google Earth)

Within a couple of years, sediment had begun to accumulate and rebuild marshy wetlands. (Image: Agriculture Department Farm Service Agency via Google Earth)

Ten years after the diversion was cut, 150 new acres of new wetlands have filled the area, and some trees are growing there. Officials expect the river to continue building and nourishing the new land for many decades. (Image: Google Earth)

Note: Two of the planned southeastern diversions are located off the map west of New Orleans.
Sources: Andy Nyman, professor of ecology at Louisiana State University; Todd Baker, biologist director at the Louisiana Dept. of Wildlife and Fisheries; Louisiana Coastal Protection and Restoration Authority

Rising seas, sinking land

The crown jewel of New Orleans’s impressive new hurricane protections is a 1.8-mile-long, 25-to-26-foot-high surge barrier across a marsh landscape that includes the much-loathed Mississippi River Gulf Outlet — the MRGO, or “the Mr. Go” as locals sometimes call it — an artificial channel through the wetlands that was widely blamed for funneling Katrina’s storm surge straight at New Orleans. At $1 billion, the barrier is the largest structure the Army Corps of Engineers has ever built. Its concrete walls, reinforced with eight Eiffel Towers’ worth of steel, are designed to stop any storm surge that comes at the city at this most vulnerable of points. A complementary series of walls protects a 133-mile circuit around the larger metropolitan area, providing vastly stronger defenses, as much as 32 feet high in some places.

“The protection system is now light-years ahead of where it was 10 years ago when Katrina hit,” says Rick Luettich, who is director of the Institute of Marine Sciences at the University of North Carolina at Chapel Hill and served on a major National Academy of Sciences panel studying New Orleans’s protections. The protections are designed to fully stop the storm surge of a one-in-100-year hurricane — roughly a Category 3 storm.

There is certainly an argument that New Orleans ought to be protected even more — up to a Category 5 level. But Luettich emphasizes that even in a stronger storm, the new defenses make the risk of catastrophic levee or seawall failure — as happened in Katrina — less likely.

The problem, though, is that walls are not all that New Orleans needs as it stares down a future of rising seas and sinking land.

“After Katrina, there was a consensus developed that we need to do two things,” says Don Boesch, a New Orleans-born wetland scientist and president of the University of Maryland Center for Environmental Science. “One is stabilize and maintain the coastal landscape, to provide a context in which you are living rather than an island surrounded by a big wall in the gulf. And second, you needed to make honest-to-goodness, robust flood defenses.”

“They’ve done a good amount of work to accomplish the latter,” Boesch says, “but it’s been slow on the former.”

From wetlands to walls

See drone footage of hurricane protection areas, an existing freshwater diversion project in The Mississippi River, and fishing communities outside New Orleans.
Play Video

Linda Davidson (The Washington Post)

Viewed from the top of the sea wall, the wetland fringe is thin and short — there is open water and grasses but no trees. Inside one of the structure’s massive gates, meanwhile, each foot of elevation is ticked off on the side, up to 26 feet.

By 2100, according to the United Nations’ Intergovernmental Panel on Climate Change, the water may have risen so much that it is up to the three-foot marker. And that does not take into account additional sea rise that will occur simply as a result of the land’s sinking. What’s more, the IPCC is increasingly being criticized as being too conservative. Some scientists have begun to talk about considerably more water falling into the seas from the planet’s ice sheets during this century, although there is no consensus as to how much is possible.

Every coastal city in the world faces a version of this problem. But scientists who study river deltas and wetlands consider New Orleans to have a critical advantage. Unlike Miami and New York, it is built on one of the world’s great rivers, one that naturally built a vast delta over the past 5,000 to 6,000 years. What better way to combat sea-level rise than that?

But instead of using the river, what has happened from a large-scale geophysical standpoint looks more like full surrender. With the river leveed to prevent flooding and to support shipping interests — and dammed upstream, reducing its available sediment — it cannot build wetlands as it once did. Meanwhile, the wetlands have been sliced up by oil and gas interests that have laid pipelines across them and by the government for controversial navigational projects such as the MRGO.

Add all that to sea-level rise and natural land sinking, and Louisiana has lost an unfathomable amount of wetland area. Between 1932 and 2010, it lost 1,900 square miles’ worth, an area almost the size of Delaware, according to the U.S. Geological Survey. And every day, more vanishes.

“We need to get started on all of this as soon as possible, and the longer we wait the more difficult it is to overcome the processes of increased sea-level rise and subsidence [land sinking],” says Harry Roberts, an emeritus professor of geology at LSU.

New Orleans’s $1 billion storm surge barrier

See drone footage of the 1.8-mile-long, 25-to-26 foot-high Lake Borgne Surge Barrier, which is supposed to protect New Orleans against the one-in-100-year hurricane.
Play Video

Linda Davidson (The Washington Post)

The battle over diversions

The state’s 2012 coastal plan laid out a variety of large projects to restore wetlands, not all of them dependent on diversions. Another pricier technology called marsh creation involves using soils dredged from the river bottom and then pumped long distances to build new islands or wetlands. Diversion opponents say this is the way wetlands should be restored. But coastal and wetland scientists say the land-building power of the river itself needs to be harnessed.

“There is an overwhelming consensus that that is ultimately going to be the primary mechanism to restore the delta,” says Tornqvist, the Tulane geologist.

The master plan found that “sustainable restoration of our coasts without sediment diversions is not possible.” For the southeastern Louisiana coast, it envisioned four very large ones that would pour water into St. Bernard and Plaquemines parishes. The largest diversion under current consideration would carry water at up to 75,000 cubic feet — or nearly one Olympic-size swimming pool — per second.

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“It’s a gravity-driven process,” says John Wells, dean of the Virginia Institute of Marine Science and chair of a state advisory panel that is examining the diversions. Unlike marsh creation, creating a diversion is a one-time cost for the state, Wells says. Once you build it, the river does the rest of the work.

That’s not to say that the diversions will represent automatic salvation. Wetland scientists from the U.S. Geological Survey and Western Washington University who studied the diversion plans, as well as the Louisiana coastal plan as a whole, have rendered a sobering verdict on them. Without the coastal plan, in a “do nothing” scenario, Louisiana is forecast to lose an additional 800 to 1,800 square miles of wetlands in the coming 50 years — nearly another Delaware at the high end. With the full plan including the diversions, by contrast, the wetland scientists forecast that 40 to 75 percent of the land loss might be prevented. “Net loss of wetlands in coastal Louisiana is likely to continue,” they conclude.

In other words, the diversions, and the coastal plan as a whole, are fundamentally about stanching the bleeding — and giving New Orleans and the Louisiana coast a fighting chance. Even that, though, is controversial.

Robin, the oyster farmer, says his family’s 10,000 acres of oyster leases in coastal Louisiana will be devastated if huge pulses of fresh water flow across the area. (Oysters depend on a delicate balance between fresh water and salt water). His father went into the seafood business nearly 70 years ago, Robin says, and the business managed to survive the devastation caused by the region’s two biggest catastrophes — Katrina and the 2010 Deepwater Horizon oil spill. But the diversions would truly be the end, he says, and he doesn’t want compensation for his losses, either.

“I don’t want a handout,” Robin says. “I want to do what I know I can do. I love what I do. I could have retired, as young as I am, but I spent the fortune in rebuilding my reefs and boats for my kids and my grandkids to do it.”

Many other fishermen tell similar stories, and they have banded together with local fishing interests in the Save Louisiana Coalition, the core organization opposing the diversions. “Coastal communities, like Saint Bernard Parish, rely on the economy of the fishing industry,” says George Ricks, a charter-boat captain who is president of the coalition. “And if we lose that, it’s going to be a kill shot to the economy of Saint Bernard.”

But not all locals are opposed to the diversions. Wetlands could provide a huge economic value by nourishing wildlife and fisheries, leading to tourism, hunting and fishing opportunities. And Jimmy Delery, a St. Bernard Parish resident and coastal advocate who traces his ancestry to the French founding of New Orleans, points out that the opponents are profiting from the status quo. “We cannot take the short-term economic gains of one area of fishing and bet that against the long-term gains of culture and generations to come,” he says. “And that’s where the problem lies.”

Most of the fisheries would not be where they are now if not for another effect of wetland loss: saltwater intrusion. Constant channels cut into the marshes by oil and gas interests, and to help promote shipping, have given the advantage to salt water over fresh water. Rising seas have the same effect. So the saltwater front has moved inland.

“If you ask some of those fishermen where their grandfather used to fish, it would likely be a distance from where they’re fishing today,” says Jeff Hebert, the chief resilience officer for the city of New Orleans.

In the Violet Canal, one of the waterways in St. Bernard Parish that leads out to the MRGO, you can see the combined consequences of saltwater intrusion, sinking land and rising seas. Along the sides of the canal, it is easy for a boat motor to get temporarily stuck on the stump of a drowned cypress tree — proof that the land used to be a lot higher and the water system fresher. Cypress is a freshwater species — and one of the trees most effective at stopping hurricane storm surges.

“When I was a kid, I remember . . . us pulling the boat right into the cypress trees,” Delery says of the Violet Canal area. “The trees were so enormous, I thought Tarzan was going to come out of them.”

Now the landscape is mostly a low-lying marsh, with vegetation growing only a few feet from the ground.

The fishing communities outside New Orleans

See drone footage of Yscloskey and Shell Beach, La., which are fishing communities where many oyster and shrimp fishermen are based. Many fishermen oppose a plan to divert the Mississippi River in an effort to save wetlands, because they say it will destroy their industry.
Play Video

Linda Davidson (The Washington Post)

Delays ahead

The stakes in the diversion conflict are rising. Wetland restoration has long been a stepchild compared with hurricane protections, in part because of an inability to fund the state’s $50 billion coastal plan. But that may soon change as Louisiana’s share of the $18.7 billion BP settlement over the Deepwater Horizon spill begins to flow to the state and is expected to be used to help advance the plan’s implementation.

The Louisiana Coastal Protection and Restoration Authority, the state agency administering the coastal master plan, will “make a decision before the end of the year on whether we will go forward with the concept of sediment diversions as a tool to replenish and grow our declining marsh estuary ecosystem,” Chip Kline, chair of the authority, said in a statement. He added that in this scenario, it would still take an additional four to five years to begin construction on the first diversion.

That may give time for opponents to make considerable headway, particularly when it comes to forging political alliances. One argument that has already surfaced is that wetlands offer only limited protection against hurricanes. Still, Nyman, the LSU ecologist, said that “the wetlands that have been lost up until Katrina probably would have made the storm surge during Katrina lower.”

In the end, the problem is that the success of wetland restoration, in the face of rising seas, is far from a certainty even if the state throws everything it has at the problem — including the river. Scientists know that marshes rise as sediment arrives and plants grow, but do they rise fast enough? That is unclear. And even if diversions are built, the rate of sea-level rise will depend on factors that are far beyond Louisiana’s control, such as global emissions cuts and the stability of planetary ice sheets.

“The reality is, even the most beautiful, successful, clever river diversions are not going to be able to keep up with rising sea levels if climate change goes on unabated,” Tornqvist says.

Nonetheless, the hope remains — as does the necessity of taking action to protect the Louisiana coast and its beating heart, New Orleans. Nyman, for one, says he wants to retire here. And to hear him talk, standing atop new land on the verge of the gulf, makes one think it just might be possible to ensure that the city of jazz and gumbo is still with us, and vibrant, in 2100 and beyond.

“I literally am older than dirt,” Nyman says. “This dirt was put here after I was born.”

Katrina survivors a decade later

A multimedia project shows the lives of those who stayed after Hurricane Katrina on those who decided to move on. See where some of those people stood in the early months after the disaster, and where they stand now.

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Katrina survivors a decade later

A multimedia project shows the lives of those who stayed after Hurricane Katrina on those who decided to move on.

Drone video: Footage of post-Katrina wetlands

See drone footage of hurricane protection areas, an existing freshwater diversion project in The Mississippi River, and fishing communities outside New Orleans.