NEW ORLEANS, La. (WVUE) - On the east bank of Plaquemines Parish, coastal scientist Dr. John Lopez visits Big Mar, a former agricultural site which turned into a mostly rectangular lake after its levees failed decades ago.
These days, the site undergoes another transformation.
“Most of what was that lake is now a delta,” Lopez said.
Lopez -- the Director of the Coastal Sustainability Program for the Lake Pontchartrain Basin Foundation -- credits sediment flowing from the Mississippi River through the nearby Caernarvon Fresh Water Diversion.
“Starting around 2005, we started seeing new wetlands developing,” Lopez said, “And actually, there’s now a small delta."
He points out Caernarvon was never designed to build land, only to deliver a fresh drink to the nearby marsh.
To the commercial fishermen who ply the waters of nearby Breton Sound, that sounds like something from a different universe.
Ryan Guerra points to his oyster crop, nearly wiped out after this year’s unprecedented back-to-back openings of the Bonnet Carre Spillway 20 miles upriver from New Orleans.
“They just can't live in that fresh water,” Guerra said.
He and many other fishers cite fresh water and nutrients from fertilizer, running off from farms primarily in the midwest.
They fear similar results if the state of Louisiana follows through with plans for the most expensive coastal restoration projects in its history -- twin sediment diversions proposed for each bank of the river in Plaquemines.
The Louisiana Coastal Protection and Restoration Authority [CPRA] has applied for permits to build the Mid-Barataria Sediment Diversion on the west bank and Mid-Breton the east bank.
The diversions could pour up to 75,000 cubic feet per second of water into nearby bays with the aim of mimicking the river’s land-building powers.
This spring, the spillway opening peaked at 168,000 cfs, poured into Lake Pontchartrain and eventually into nearby lakes and bays.
“You have a massive amount of water, much more than is proposed with any of the diversions,” Lopez said.
In 2013, he coined the name Mardi Gras Pass for a spot on the east bank where the river had blown through its banks and reconnected with an old canal.
While Lopez has said the pass could serve as a sort of free diversion, fishermen blame fresh water pouring into bays on the east side of the river with compounding their problems.
“That’s what’s started killing off this side,” Guerra said.
On a boat making its way through Mardi Gras Pass, coastal activist Foster Creppel sees a return to something more like the nature he intended.
“We’re not supposed to have a saline delta,” Creppel said. “This was a fresh water estuary and delta.”
He pointed out some fishermen even harvested crawfish this year about a mile from Mardi Gras Pass.
“Look at the possibilities of what's to come if we had a very healthy delta again,” Creppel said. “We’d have lots of people working in the crawfish industry.”
However, critics believe the spillway has adversely affected other forms of marine life, including bottlenose dolphins, which have died by the dozens this spring and summer.
Moby Solangi, president of the Institute for Marine Mammal Studies in Gulfport, said he fears another dead zone in the Gulf of Mexico.
Each year, fertilizers stimulate algae, which die off and use up oxygen as they decompose. NOAA scientists estimate this year’s dead zone could stretch over 7,829 square miles, roughly the size of Massachusetts.
“More power to Louisiana,” Solangi said. "They want 10,000 square miles of their waterfront properties to be dead zones, great. But don’t give it to Mississippi.”
Diversion supporters in Congress also worried about the potential negative impacts on dolphins. They directed federal agencies to ignore the Marine Mammal Protection Act when performing the required environmental impact studies for the projects, arguing that environmental laws passed in the 1970s never envisioned wide-scale restoration efforts.
“To say, ‘let’s not worry about the top dog in the sea, everything will be just fine,’ it’s concerning,” Solangi said.
Lopez argues none of what has been experienced this spring and summer relates directly to what the diversions would entail.
“The system right now is almost completely flushed with fresh water, almost to the Gulf of Mexico,” Lopez said. “That is not what is proposed and I do think it is an unfair comparison."
Like some other scientists, he is reluctant to jump to conclusions about what is leading to the dolphin mortality.
Fresh water could be only one factor, but Lopez said it could be more than just that.
“Even after the fact, it’s not always 100 percent clear. A lot of times it’s more than one thing going on," Lopez said.
The two sides of the argument often point to the same places on the map to make their case.
While supporters cite the new Caernarvon delta, critics point to nearby Breton Sound, where Hurricane Katrina in 2005 steamrolled over the marsh, wiping out a huge swath of land in mere hours.
“Caernarvon, I'll take you back there,” Guerra said. “It's all open lakes, where it was all land."
Diversion opponents often site studies which suggest as river water turns an ecosystem more fresh, it promotes plants with weaker root structures than in a salt water marsh.
Still, others point out the Breton Sound wetlands -- made largely out of organic material -- were collapsing before Katrina, as oil field canals sliced and diced the marsh, drawing in salt water and ruining the tidal flow.
Lopez points back to Caernarvon.
“Cypress trees we planted in 2012 were covered by 18 feet of salt water [in Katrina], and they did perfectly fine,” Lopez said.
South of Morgan City, a canal cut in the 1940s in the Wax Lake area built a surprise delta.
Lopez said the river is connected with the marsh on a smaller scale in 15 or 20 other places, “and all of them are building land."
A recently released U.S. Army Corps of Engineers computer model predicted net land gain near the proposed diversions, but a net loss farther from the outlets, where a "reduction in plant productivity induces an acceleration of land loss.”
The model was created as part of a joint state-federal hydro-study of the Mississippi River that was never completed.
Mark Wingate, deputy district engineer for programs and project management in the Corps New Orleans District said there are other things to consider.
“You have to know that the models are just one piece of information,” Wingate said. “They’re not the only information."
No model can duplicate nature perfectly, Wingate said.
“The modeling that we’re discussing here is from the 2017 time frame,” Wingate said. “It recognized that we need to better understand what would happen to vegetation when you inundate it.”
That Corps technology has been incorporated into the model the state and regulatory agencies are now using for the proposed diversions, according to a CPRA spokesperson.
The model is based largely on a 3D computer model from Deltares, a highly-regarded water institute in The Netherlands.
“We’ve been studying this delta for almost 100 years,” Lopez said, "Intensely for the last 30 or 50 years. We know a lot.”