Tulane researchers see a ‘win-win’ in finding alternatives to using the Bonnet Carré weir to prevent flooding

NEW ORLEANS (WVUE) — A new study from Tulane University finds that two proposed diversions of the Mississippi River could reduce the need to operate the Bonnet Carré Spillway while providing benefits for Louisiana’s coast.

“We’re reducing the potential impact of large square cap releases, while making better use of those resources,” said Tulane professor Ehab Meselhe.

The Bonnet Carré, the giant relief valve that the US Army Corps of Engineers operates upstream from New Orleans, has prevented river floods since the 1930s.

However, critics complain that it produces collateral damage, pumping trillions of gallons of fresh water and nutrients into Lake Pontchartrain and surrounding bays and harming marine life.

The spillway’s repeated openings in recent years have increased calls, including from the Mississippi Gulf Coast, to seek alternatives.

Meselhe and his team used numerical modeling to show how the proposed Union diversion on the east bank and Ama diversion on the west bank could improve river management and reduce the volume of water flowing through the spillway.

Three-dimensional computer models were used to predict the effects of river water flowing through marshes and swamps

“On both sides it’s new swamps,” Meselhe said. “So providing them with fresh water and nutrients will help them fight salinity intrusion.”

The study was funded by the Environmental Defense Fund, which has been a strong supporter of the concept of using the river to rebuild wetlands.

In the coming decades, scientists warn that the Louisiana coast will face even more threats as sea levels rise and the delta sinks.

The Union Diversion would provide a glass of fresh water to a cypress swamp threatened by too much salt water, eventually flowing from Lake Maurepas into Lake Pontchartrain and into the Mississippi Strait.

“Certainly this will have a positive impact on the salinity regime in Mississippi State,” Meselhe said.

“In theory, yes, the swamp is supposed to clean things up,” said Dr. Moby Solangi, president and executive director of the Gulfport Institute for Marine Mammal Studies and a critic of river diversions.

Solangi fears that the system “will be overwhelmed”.

He advocates for more frequent use of the Morganza Spillway north of Baton Rouge.

“The opening of the Bonnet Carré spillway in 2019 was a major factor in people realizing the damage these diversions can cause,” Solangi said. “I think it was a watershed moment.”

Meselhe and other supporters of the two hijackings are hoping the corps will eventually jump on board, “to also see if they can consider adjusting the way the river is run.”

The projects, even if approved by Congress, would take years to design, design, and build.

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