Posted on November 4, 2026
Arthur Matherne is used to speeding his airboat across a southeastern stretch of the Louisiana coast where lakes and bayous have widened as the Gulf of Mexico’s salty water has moved in, dissolving marshes and swamps.
But in one tucked-away patch of the Barataria Basin’s 1.6 million acres, the semi-retired tour guide eases off the throttle as he tries to remember his way through channels that have grown tighter by the year. Grasses are overtaking the shallows, and oak branches are spreading overhead, dangling Spanish moss over waterways he once barreled through.
“All this, it’s filling in,” Matherne said after shutting off his airboat’s roaring propeller. “Right here, it used to be three feet of water. Now it’s three inches.”
What Matherne is seeing is a striking reversal of a pattern that has defined southern Louisiana for the past century. While much of the coastal zone has receded at about 11 square miles per year from erosion and other forces compounded by climate change, the wetlands here are gaining ground.
The reason is just a few miles away. Near Luling in St. Charles Parish, the Davis Pond Freshwater Diversion has funneled Mississippi River water into the basin since the U.S. Army Corps of Engineers built it in 2002 to combat saltwater intrusion. But something unexpected happened. The diversion also carried the muddy river’s sediment into the wetlands, raising the bottom and helping create new land.
“It’s had this unintended consequence of building land,” said Jacob Berkowitz, an Army Corps of Engineers wetland scientist. “This became one of the strategies that’s considered a key to addressing coastal land loss in Louisiana.”
Yet even as Davis Pond demonstrates the land-building potential of river diversions, Louisiana has abandoned its most ambitious attempt to put that approach to work. Last year, the state canceled the massive Mid-Barataria Sediment Diversion, a $3 billion project inspired by Davis Pond and once heralded by the state as “the largest and boldest environmental restoration project in U.S. history.” Though it broke ground in 2023, work stopped shortly after Governor Jeff Landry, a Republican and one of the diversion’s most prominent critics, took office in 2024. He officially terminated the project, which would have been located 20 miles south of New Orleans, in July 2025.
Landry called the diversion a costly and ineffective “experiment” that would harm the commercial fishing industry by flooding parts of Barataria Bay with too much fresh water and sediment, pushing out shrimp and burying oysters.
“This project is going to break our culture,” Landry told state lawmakers in 2024. “It will destroy the shrimping industry — which is already struggling — and destroy the oyster beds.”
Landry’s administration also canceled a companion project — the $1.8 billion Mid-Breton Sediment Diversion, aimed at reviving dying wetlands southeast of New Orleans.
Despite Landry’s opposition to these projects, his administration is quietly planning more diversions along the Mississippi, albeit on a smaller scale.
Officials with the Louisiana Coastal Protection and Restoration Authority, or CPRA, declined to discuss the state’s diversion plans, but a Verite News review of the authority’s budget documents indicates the state plans to spend at least $340 million on five projects over the next several years that would divert Mississippi River water to restore coastal wetlands. That represents a big increase over past spending on diversions. Since 2007, CPRA has completed just three diversion projects totaling $47 million, according to the agency’s 2027 annual plan.
While some state leaders may disparage diversions, CPRA scientists still believe using river water to rebuild land and restore wetlands is a sound approach. At its core, a diversion mimics how the Mississippi functioned before levees walled off its floodplain, preventing the river from overflowing its banks or breaking through them at points called crevasses, according to Brian Gossman, a CPRA coastal scientist, who spoke at a public lecture in March.
“The natural process that we’re attempting to harness is the Delta cycle,” Gossman said. “It’s the same process that built all of coastal Louisiana over millennia. We’re just using it in a targeted way.”
Nearly
all of the CPRA’s diversion spending would go to one project — the restoration of Maurepas Swamp, a Chicago-sized wetland along the west edge of Lake Pontchartrain, about 25 miles from New Orleans.
The $334 million project, which broke ground in 2024, will install gates in the Mississippi River levee near Garyville in St. John the Baptist Parish and channel up to 2,000 cubic feet per second of water into Maurepas, which remains one of the country’s largest swamps despite losing thousands of acres of cypress and tupelo forest. Levees built in the early 1900s cut the swamp off from fresh water and sediment, leaving its trees vulnerable to saltwater intrusion.
According to CPRA, the diversion will rebuild lost land and flush out stagnant, salty water, rejuvenating about 45,000 acres. It’s set for completion late next year.
The authority hasn’t totally given up on diverting sediment into the Barataria Basin. After canceling the Mid-Barataria Sediment Diversion, the agency dusted off an earlier, much smaller version of the project: the Medium Diversion at Myrtle Grove. Proposed more than 25 years ago, the project would divert up to 15,000 cubic feet of river water per second into the basin — about one-third of Mid-Barataria’s typical operating rate. To speed up the creation of marsh, the authority would also dredge sediment from the Mississippi and pump it directly into the basin.
The Myrtle Grove project’s timeline and budget are unclear. CPRA’s budget documents indicate about $1.7 million could be spent on it between 2027 and 2029, but the full cost will likely be much more. In 2012, the project was estimated at $278 million, or about $480 million in today’s dollars.
CPRA’s spending plans would also boost the Davis Pond diversion. The agency has proposed spending $3 million, shared with the Army Corps, to study how the diversion could be operated to build more land.
Research led by Tulane University in 2019 suggested that boosting the diversion’s average flow from 1,000 cubic feet per second to between 4,000 and 7,000 cubic feet per second could deliver more sediment to nearby wetlands. But if the flow is too high, researchers warned, the sediment will be flushed away.
In St. Charles Parish, home to Davis Pond, finding ways to increase the diversion’s flows has strong support. In its 2025 habitat restoration plan, the parish endorsed the proposed CPRA study, citing criticism that the diversion’s operations were “not being aggressive enough” to maximize its benefits.
