Posted on February 15, 2023
Drive through Maurepas Swamp and it may appear lush and thriving. But over the past century, the swamp has been slowly dying.
New trees are few and far between, and the ones there are struggling to stay alive. If the trend continues, Louisiana could lose one of its largest freshwater swamps and a major buffer between Baton Rouge and hurricanes.
Soon, construction of a new $760 million, 17.5-mile West Shore Lake Pontchartrain levee system is expected to provide long-awaited flood protection across three parishes but could damage up to nearly 11,000 acres of the struggling swamp in the process.
But a first-of-its-kind partnership between the state’s Coastal Protection and Restoration Authority and the U.S. Army Corps of Engineers will ensure the same area hit hardest by building the levee will be restored.
In a break from the past, the federal government signed off on using a Mississippi River diversion planned alongside the levee to mitigate for construction. The $300 million River Reintroduction Into Maurepas Swamp will reconnect the region to the river to deliver nutrients, fresh water and sediment to improve the health of its towering bald cypress and tupelo trees.
Coastal Protection and Restoration Authority project manager Brad Miller explains the benefit of a new partnership between the state and the U.S. Army Corps of Engineers during a tour of Maurepas Swamp on Friday, Feb. 3, 2023.
“It’s the first time that the Corps is using a CPRA-built restoration project for mitigation,” said Brad Miller, the state’s project manager for the diversion, during a trip to the swamp on Feb. 3. “In doing that, it’s gonna allow both projects to be built concurrently, saving time and money.”
State officials and coastal advocates toured Maurepas on the Blind River earlier this month to look at the state of the trees. Turn down one of the canals, and the forest canopy grew choppy – and not just because the trees had dropped their leaves for the winter.
Slim cypress trunks and topped-off tupelos signaled that the trees spent more energy on survival than growth. In turn, the region’s wildlife has also suffered, resulting in things like fewer birds. As an example, boat captain Kirk Songy said duck hunting was abysmal.
“We’re known as the Sportsman’s Paradise, right? But this area in the last 20 years, we haven’t seen any ducks lately,” Songy said as the boat idled near a patchy area of swamp.
The two-mile-long freshwater diversion will have a peak flow of 2,000 cubic feet per second, enough to revitalize more than 45,000 acres of one of Louisiana’s few remaining freshwater coastal swamps, according to the state’s coastal authority. The flow should be enough to feed the swamp and also help flush out any saltwater pushed into the sensitive habitat by hurricanes.
Two older cypress trees stand side-by-side on the edge of the Blind River on Friday, Feb. 3, 2023, draped with spanish moss.
Meanwhile, the levee project will address the residents’ dire need for storm surge protection in St. John, St. James and St. Charles parishes. Hurricane Ida sent devastating floodwaters into the region in 2021.
Proposals for the massive risk reduction levee system date back decades to the 1970s, but cost blocked it from progressing until the passage of the Bipartisan Infrastructure Law just under three months after Ida.
The levee will extend from the Bonnet Carre Spillway to Garyville, reducing property risk from flooding associated with a so-called 100-year storm, or a storm that has a 1% chance of happening in any given year.
Legally, any project that damages wetlands is required to replace what’s lost. That can be done through a number of methods, and the most popular way relies on so-called mitigation banks.
The banking system allows government agencies or private companies to purchase credits from other companies that are rebuilding habitats to balance out damage from new construction. But sometimes the credits come from areas restored far away from the project’s impact, raising questions about whether the area benefits.
Agencies and companies prioritize buying credits for restoration within the same basin as their projects, but if not enough are available, they can buy in neighboring watersheds, according to Miller and Corps assistant deputy engineer Nick Sims.
Louisiana Wildlife Federation policy manager Stacy Ortego said there weren’t enough swamp credits available for the Corps to purchase from a bank, forcing them to look at other options like building their own restoration project or using the state’s diversion. After three years of analysis, the Corps decided to use the latter option in January to mitigate the harm caused in Maurepas Swamp.
The Corps will still rely on traditional mitigation banks to account for the levee’s damage to other habitats like wetlands and bottomland hardwood forest.
A sign on a tree in front of Our Lady of the Blind River church warns of a no wake zone in this portion of the Blind River within Maurepas Swamp on Friday, Feb. 3, 2023.
Sims and Miller said the proximity of the levee’s footprint and the restoration project is part of what makes the partnership special – and could provide a model for other work in the state.
“When you see how you have the partnership between federal and state agencies to where you’re syncing two projects that share the same footprint, that share the same features, this really could be the blueprint for future mitigation projects,” Sims said.
Now that the levee and diversion are tied together, construction of both will happen simultaneously over the next four years. Sims said the Corps has already broken ground on constructing the first mile of the levee system.
Final costs of both projects are expected to increase largely due to high inflation, which has sent construction costs across the state skyrocketing for everything, from coastal restoration to roads and bridges. The state expects to save by spending less on its share of the levee cost as a result of their work on the diversion.
