Casts + Blasts
As the state of Louisiana is ready to invest close to $2 billion on Mississippi River sediment-diversion projects to replenish sinking and eroding wetlands, questions surface about the potential effects on the estuarine marine life.
Before the Mississippi River’s extensive levee system was built, sediment flowed freely into southeast Louisiana’s marshes and swamps when the river overflowed its natural banks. Now, much of the sediment stays in the river and gets channeled into the Gulf of Mexico instead of spilling out to surrounding wetlands.
The state of Louisiana plans to build two large sediment diversions in Plaquemines Parish as major tools for estuary restoration, replicating the Mississippi River’s wider flow of sediment while keeping levees intact.
As reported by the Times-picayune, the $1.3 billion Mid-barataria Sediment Diversion would send as much as 75,000 cubic feet per second of water and sediment to Barataria Bay during high-river periods — through a controlled opening in the West Bank levee near Myrtle Grove — to reduce land-loss rates and sustain wetlands damaged by the BP oil spill; the $696 million Mid-breton Sediment Diversion would allow up to 35,000 cubic feet per second of water and sediment to flow into Breton Sound, introducing 70 million tons of sediment to the basin over 50 years.
Many conservation groups support the diversions, but both projects are raising concerns about the effects on marine life and certain wildlife species. While the long-term impacts of the state’s plan to unleash the Mississippi River into its coastal marshes
are the focus of studies and much discussion, many of Louisiana’s commercial and recreational fishers believe more needs to be done to understand the effects in the first five years of the projects.
State officials recently conducted a survey that asked people — mostly involved directly in Louisiana’s fishing industry — questions about the state’s plans for the Mississippi River diversions; 98 percent of those surveyed considered it essential to focus on the short-term ecological and economic impacts.
How the diverted river water would change salinity in the bays was the biggest concern, followed by the flow rate of the diversions and the time of year when they would be opened, since the excess of fresh water could kill oysters and drive shrimp, crabs and fish farther out into the Gulf of Mexico.
“People can no longer question whether the Mid-barataria Diversion is going to happen,” said Patrick Banks with the Louisiana Department of Wildlife and Fisheries. “It’s coming!” The Trump administration agreed in January to speed up permitting for the project, but an environmental review will still be required.