Sinking, soggy south Louisiana has been losing ground, literally, for decades: The southern part of the state lost about 1,800 square miles from the 1930s through 2010. 

Recent major hurricanes haven’t helped. Between 2005 and 2008, Katrina, Rita, Gustav and Ike destroyed more than 300 square miles of marshland. 

Since Katrina, in 2005, authorities have spent billions of dollars on hurricane defenses, and a good share of that has been for restoring coastal marshes and barrier islands.

On Wednesday,  search-and-rescue teams were still looking for bodies in the aftermath of Hurricane Ida—a Category 4 storm that delivered sustained, 150 mph winds when it struck Louisiana Sunday. But state officials and others were anxious to know how the coastal projects and shorelines weathered the cyclone.

After Katrina, mitigation measures like new flood walls, levees and pumping stations helped hold back the water and protected New Orleans from flooding as Ida dumped as much as 10 to 18 inches of rain in some areas, knocked out power to millions amid soaring temperatures and humidity, and disabled water and sewer systems.

But Ida also delivered the biggest post-Katrina test yet in the state’s epic and costly battle to save its fragile coast, and answers to the question of just how well those restoration efforts fared will emerge in the coming days and weeks.

“Ida was and is a severe test on both our restoration projects and our protection projects, designed to protect our communities from just these kinds of events,” said Bren Haase, executive director of the Coastal Protection and Restoration Authority, created in the aftermath of Katrina.

The authority may send airplanes over coastal restoration projects this week for a preliminary look, Haase said. He said he anticipates that work that has already been completed will be in good shape. But he is concerned about a few large island and marsh restoration projects that are still under construction and so exposed. They include a $100 million project to raise and reshape the West Grande Terre barrier island and the $32.3 million restoration of 430 acres of coastal habitat on Caminita Headland in Lafourche and Jefferson Parishes.

“I am worried about those, honestly,” Haase said. Newly spread sediment is fresh and not snugly in place, he said. “There can be some damage.”

A Coastline Facing Compounding Threats

With global warming raising sea levels and contributing to more powerful and dangerous hurricanes that tear across land already sinking under its own weight, Louisiana’s low-lying coast, including what remains of the Mississippi River Delta, faces enormous challenges, including the accelerating loss of land to the Gulf of Mexico. The disconnection of the Mississippi River from coastal marshes by levees limited sediment deposition that had served to replenish soils in the vanishing delta, speeding its disappearance.

Coastal losses will only get worse unless the nations of the world can put the brakes on greenhouse gas emissions that are driving sea level rise, scientists say.

While researchers cannot yet make claims with a high level of confidence about long-term trends in the frequency of hurricanes and tropical cyclones, the Intergovernmental Panel on Climate Change report published in August expressed confidence that there will be more frequent storms that like Ida, are Category 4 or Category 5, the highest intensity categories. 

A 2019 study found that 100-year floods will happen every one to 30 years if greenhouse gas concentrations in the atmosphere keep increasing, because global warming is raising sea level and transforming tropical storms. 

“We cannot ignore the changes of hurricanes in the future,” said co-author Reza Marsooli, an engineering professor at the Stevens Institute of Technology. 

However, he said, coastal Louisiana still can bolster its defenses. The state has “a unique opportunity to exercise nature-based solutions, like salt marshes, and engineered solutions, like seawalls and levees,” Marsooli said. “It’s an interesting place to practice these types of hybrid solutions.”

Marshes, for example, can absorb wave energy and reduce storm surges from hurricanes, he said.

Marsooli compared a storm making landfall to a person wearing socks. On a slick hardwood floor, socks slide, but a marsh is like carpeting. “If I try to slide on a carpet, I don’t slide, because of the friction,” he said.

Costly, Elaborate Protections and Restorations

Since 2007, the Coastal Protection and Restoration Authority, with federal and non-federal partners, has secured $21.7 billion in funding for projects across 20 Louisiana parishes. Crews have constructed 60 miles of barrier islands and berms, along with 336 miles of levee improvements. About $14 million went to shore up flood control in New Orleans after the catastrophic failure during Katrina, a hurricane that caused more than 1,800 deaths.

The state’s current plan calls for spending about $1 billion a year, well into the future, with money from settlements with BP in the aftermath of the 2010 Deepwater Horizon oil spill, as well as federal and state sources.

The plan, which is being updated for 2023, lays out what’s at stake, projecting coastal conditions 50 years in the future under three scenarios. Even its most optimistic outlook envisions losing another 1,207 square miles of land in the state, while doing nothing would result in more than 4,000 square-miles being lost.

Projects are evenly split between restoration and protection, said Emily Vuxton, the policy director for the Coalition to Restore Coastal Louisiana.

“We’re going to lose a lot of land,” she said, but added, “we can sustain a smaller delta with these efforts, plus still provide services that the nation needs, like shipping in the Mississippi River.”

That work can include replenishing beaches with sand, installing rock walls and restoring oyster reefs. Other projects involve using heavy equipment to build earthen containment dikes, filling them in with huge volumes of sediment from the bottom of the Gulf of Mexico and replanting vegetation,  or dredging clay and sand from the bottom of the Mississippi River and sending it 20 miles through pipelines to bolster the coast. 

It is a tough and costly one in which to carry out lasting barrier island and marsh restorations, because the area is sinking so fast with sea level rise, said Robert S. Young, director of the Program for the Study of Developed Shorelines and professor of coastal geology at Western Carolina University. 

Restored and natural barrier islands face unique challenges to their survival, Young said. “The rate of land subsidence is pretty high, the highest of any coastal setting in the United States.” 

For example, at Grand Isle, Louisiana, south of New Orleans, the relative sea level rise, taking into account subsidence of land, is more than a third of an inch a year, according to the National Oceanic and Atmospheric Administration.

When powerful hurricanes hit restored islands, there may not be enough sand left for an island to survive the onslaught, he said, adding that he would not be surprised if some of the restoration work was damaged by Ida.

Young credits Louisiana with having a plan that sets coastal priorities and protects a lot of important nature areas. “Louisiana has almost 4,000 square miles of wetlands that’s critical habitat,” he said. “If you don’t have those barrier islands, even small storms will degrade these wetlands and marshes.”

But Young also questioned the high cost of the state’s coastal restoration program, which he said will only get higher as the environmental pressures mount. And he questioned those costs amid a lack of national planning about how to protect the country’s many thousands of miles of coastline—from Texas to New England—vulnerable to sea level rise and hurricanes, even as Congress debates massive new spending on the nation’s infrastructure.

“What we need is a real vision of where the federal priorities should be and a realistic accounting of what it would cost and where we might have a chance to hold the line,” Young said.  “Ultimately, we can spend all the money in the world, but if we don’t halt climate change, this will continue to happen.”

Protections Paying Off

So far, what’s been spent on restoration in Louisiana has been worth it, and may have helped reduce Ida’s impact, environmental advocates said.

“I think we would absolutely be in a much worse condition without the work that’s been done,” said Natalie Snider, associate vice president for the Environmental Defense Fund’s Climate Resilient Coasts and Watersheds program. Even if some newly restored areas are destroyed by Ida, coastal resilience has to be seen on a large scale, she said. EDF is part of a coalition of national and regional groups working on coastal restoration in the region.

“We know living in Southern Louisiana that coastal landscapes are what protects the coast and the levees,” she said. “The resiliency of the system is about multiple lines of defense, swamps, levees, wetlands, all of that working together. If those barrier islands had continued to degrade, that would have opened up the bays, and we would have seen way more wetlands loss.”

Some of the most potentially consequential restoration work is on the near horizon.

That will involve sediment diversion projects—a system of gates built into levees that would restore some of the Mississippi River’s natural land-creation capacity. “The muddy Mississippi, it builds land, but we have strait-jacketed it,” Snider said. Sediment diversions are the keystone to restoration, she said. “They allow water, nutrients and sediments to go out and build land.”

A final environmental review for one major sediment diversion project, the Mid-Barataria Sediment Diversion project on the west bank of the Mississippi River in Plaquemines Parish, is due next spring. A second major diversion project in the same parish, called Mid-Breton, is also in the works and under review.

Such diversions could also be used to restore ghost forests lost to elevated water levels with cypress swamps, which are “a critical part of our protection system,” helping defend communities from storm surge, Snider said.

Including the Human Factor

Louisiana has a science-based approach to coastal resilience that is far ahead of other states, said Scott Hemmerling, a cultural geographer who focuses on analyzing the societal impacts of environmental change in coastal Louisiana for The Water Institute, a nonprofit think tank based in Baton Rouge. 

But Hemmerling said coastal restoration blueprints could be improved by fully integrating local social and cultural values into the planning process at the early stages.

In a 2019 publication, Hemmerling and co-authors concluded that “coastal management practices in south Louisiana need to be more transparent and accountable to individuals and communities impacted by their actions.” They suggested several “social scientific techniques for integrating local knowledge and priorities into coastal planning processes with an eye toward cultivating social justice.”

That could help answer some fundamental resilience questions like, “Why do people stay, why do people leave? ” he said. “Are we protecting the places people value? That’s where you have to bring in social science. We need to elevate social science up to the same level as we’ve done with the physical data.”

Hemmerling advocates sharing the whole scientific process with local communities “to open the hood and let community members inform the models. We need to use the fishermen and the oystermen, and let them show us.”

That grassroots process can be intensive and time-consuming, but it might be the one thing that can help rebuild damaged trust, he said, at a time when there is a “trust deficit.”

A Spreading Threat With Potentially Overwhelming Costs

While state officials battle for the survival of Louisiana’s southern flank, Gov. John Bel Edwards this week gave an apparent nod to the federal taxpayers who have helped foot the bill for coastal protection and restoration in one of the regions that is most at risk from climate change nationally. 

Edwards thanked “people from across the country who have been generous with their investments.”

The extraordinary efforts to prevent land from falling into the sea represent a fight against an “existential threat to the people of South Louisiana,” as well as a threat to national interests, including energy and seafood production, said Haase, the executive director of the coastal authority. These efforts, he said, “are about keeping a large portion of Louisiana on the map, southern Louisiana—our culture, our identity, our homes.”

Vuxton, with the coastal coalition, called the diversions “first of their kind projects,” and “state of the art engineering,” and said that coastal restoration of marshes and islands will need regular maintenance and more money to help residents raise their homes or flood-proof businesses.

Increasingly, however, more coastal areas nationally are facing their own survival threats from sea level rise and hurricanes juiced up by global warming, and they are also vying for federal money in the name of resilience. Young, at Western North Carolina University, said the costs could be overwhelming.

“I don’t think people have a clue how much it would really cost to hold all these shorelines in place,” he said. 

Some areas will be at greater risk than others, and flood mitigation strategies should reflect those differences, said Marsooli, the Stevens Institute of Technology professor. 

“Perhaps one solution is to retreat, to leave some of the areas which are really vulnerable to sea level rise and future hurricanes,” he said. “It will really depend on the resources we have.”