NEW ORLEANS (WVUE) – Along a stretch of the Plaquemines Parish east bank, the Mississippi River is providing what coastal activists see as a no-cost coastal project.
In recent years, the river has plowed through its bank and transformed a tiny channel into the equivalent of one of the ten largest rivers in the U.S.
Neptune Pass is taking an estimated 16 percent of the Mississippi River flow during high water periods, according to Corps hydrologists.
In the process, groups active in the fight to restore Louisiana’s coast argue the river is providing a practically no-cost diversion.
“It is a restored ecosystem happening for free before our eyes,” said James Karst, Director of Communications and Marketing for the Coalition to Restore Coastal Louisiana.
Neptune Pass, they say, is depositing sediment and creating new sections of delta in both Bay Denesse and Quarantine Bay.
Not everyone is thrilled at the prospect of nature taking its new course.
Shipping interests complain the pass has already affected navigation, causing the slower-moving river downstream to build sandbars.
The Corps, which initially had planned to close the channel entirely, now envisions a dual purpose for Neptune Pass.
A draft environmental assessment envisions a two-part approach to protecting the integrity of the main river channel: a stone sill at the water bottom with a 100-foot-wide notch to reduce the outflow from the river; and 20 V-shaped mounds to further reduce the velocity of the water moving into Quarantine Bay.
The Sediment Retention Enhancement Devices, or “SREDS” as the Corps calls them, would be built of earthen material, geotextile fabric, and stone riprap.
“We allowed an opening to allow river flow and sediments to leave the river and deposit in the bay, in the receiving area,” said David Ramirez, a Corps hydrologist.
Critics of river diversions have questioned whether the new land forming in the bays was merely land that had been displaced as the river widened the channel over the years.
While computer modeling suggests that displacement has accounted for about 70 percent of the new delta, Ramirez says the remaining 30 percent has been built from sediment deposited by the river.
“The more wetlands we have between where we live and the Gulf of Mexico, the more natural hurricane protection that we have,” Karst said.
Commercial fishing interests have complained large amounts of fresh water pouring through not only Neptune Pass, but other cuts on the east bank, have dramatically altered salinity levels and devastated oyster harvests.
“There’s some innovative ideas in the report, but at the same time, there’s a lot of scientific questions that still remain,” said Alex Kolker, a coastal scientist with the Louisiana Universities Marine Consortium.
Kolker wants more detail about how the proposal would affect the river’s flow, whether SREDS would simply sink over time, and how long the flow would be sufficient to build land.
Under the Corps plan, Neptune Pass would take six percent of the river flow.
“Right now, we don’t have enough science to fully evaluate whether or not this is gonna work,” Kolker said.
The Corps is taking public comments on the proposal through the end of the month.
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