NEW ORLEANS, La. (WVUE) - On the east bank of the Mississippi River in Plaquemines, LSU coastal scientist John Day surveys a rare site along Louisiana’s coast, a place where new land forms.
“Much of this stuff is one or two years old,” said Day, professor emeritus in the LSU Department of Oceanography and Coastal Sciences, as he stood in a few inches of water in Bay Denesse.
Supporters point to this transformation to argue for Louisiana’s largest proposed coastal restoration projects, the controversial effort to divert Mississippi River water into the marsh to build or sustain thousands of acres of land.
“You see this big area of this sparse vegetation," Day said. " That’s this year, growing out over a mudflat.”
The Mississippi is depositing this new land in one of the few spots where it is unrestrained by levees.
“This how the delta formed,” Day said, “and we have to learn to use this kind of power of the river.”
Day and other scientists who recently took a boat ride into Bay Denesse pointed to some spots where the river altered the landscape in 2019."
This whole area around here has a layer of new sediment that’s 6-8 inches thick," Day said.
The state’s coastal master plan includes two large-scale diversions in Plaquemines Parish, the $1.4 billion Mid-Barataria Sediment Diversion Project on the west bank and the $700 million Mid-Breton Sediment Diversion Project on the east bank.
Critics often question the value of diversions since the land comes relatively slowly. The Mississippi took centuries to build the various delta lobes in South Louisiana at a time when several studies suggest it carried significantly more sediment than the modern river.
“From a geological standpoint, this is light speed,” geologist Paul Kemp said of the changes in Bay Denesse.
However, critics fear the diversions would bring an annual repeat of this year’s disaster for the commercial fishing industry that followed the Bonnet Carre Spillway’s two openings.
Large amounts of nutrient-rich freshwater turned nearby waterways green with algae.
While the spillway spared New Orleans from flooding, critics along the Mississippi Gulf Coast have called for the U.S. Army Corps of Engineers to find other options to manage the river.
“We believe the Mississippi River is one of the biggest threats to the Mississippi Gulf Coast,” said Blaine LaFontaine, a member of the Hancock County Board of Supervisors.
Hancock County was among a number of local governments on the Mississippi Gulf Coast to go on record as being opposed to the diversion plans.
“How we manage the Mississippi River, for not only today but the future, needs to take into consideration the adverse impacts to the Mississippi,” LaFontaine told WLOX-TV in Biloxi.
The Louisiana Coastal Protection and Restoration Authority hopes to convince skeptics that the Bonnet Carre is not a perfect analogy since it shoots water straight into Lake Pontchartrain.
Diversion supporters argue wetlands act as natural filters.
“The more we can put river water through areas like this, the more those nutrients are going to be taken out." Day said.
However, critics fear river water loaded with nutrients would also pour straight into open bays.
Because the diversions would be downriver from New Orleans, they would have no effect on the river level in the city.
Therefore, the spillway could operate in some years simultaneously with the diversions.
Over 10 years ago in Bay Denesse, the Louisiana Department of Wildlife and fisheries built terraces, sort of speed bumps, to direct the sediment flow and capture land more quickly.
Geologist Paul Kemp believes such techniques could be applied elsewhere along the coast to accelerate land building.
"These are steps that we should be taking on a large scale, I think,” Kemp said.
While the Mid-Barataria Diversion is further along in the permitting process, Mid-Breton only recently began to draw attention outside Louisiana.
Winning the required federal permit will take years with opportunities for critics to weigh in on the proposed diversion.