Neptune Pass didn’t even exist six years ago.
Now, Louisiana’s newest connection between the Mississippi River and its fish and wildlife-generating marshes moves enough water by volume that it dwarfs all but about 15 other rivers in the world. It’s a living laboratory for how a healthy, properly functioning Mississippi River Delta is supposed to work and a window into what can be expected from man-made diversions.
Located about 70 river miles south of New Orleans and directly across the river from Buras, Neptune Pass was one of dozens of narrow crevasses in the Mississippi River’s east bank in 2018, barely wide enough to pass a 24-foot bay boat through. A series of annual floods, especially a record-setting inundation in 2019, forced the river to find and exploit weaknesses along its lower east bank, an area where it isn’t hemmed in by flood protection levees.
What was a relative trickle prior to 2019 became a major pass by 2023, capturing nearly 120,000 cubic feet of water per second, or more than 15 percent of the total volume of the Mississippi during spring flooding. Almost immediately after its widening, Neptune Pass began delivering enough suspended sediment to shallow and start filling in bays and open ponds along its path and at its mouth in Quarantine Bay.
The Mississippi River was simply replicating the same processes it has employed hundreds, if not thousands, of times over the last several millennia. It utilized a weakness in its bank as an easier way to move its abundant water and sediment toward the Gulf of Mexico. If not for that natural process, most of Louisiana and a large part of Mississippi wouldn’t exist.
Preventing that natural process by blocking the river’s connection to its delta with levees is the primary reason more than 2,000 square miles of Louisiana’s coastal wetlands have already been lost.
Fish and wildlife activity
The areas adjacent to and in the outfall of Neptune Pass teem with fish and wildlife activity. Native mottled ducks, which are struggling in degrading and dying marshes across the Gulf Coast, are thriving in the emerging marshes. They are joined by migrating pintails, gray ducks, teal, mallards and dozens of other bird species. For the last five falls, the entrance of Neptune Pass and other nearby passes have been popular and productive areas for redfish, black drum, sheepshead, speckled trout, three species of freshwater catfish and white bass. Largemouth bass have been thick in connected marshes and commercial crabbers have dotted the water’s surface with trap buoys.
Ducks Unlimited and state and federal agencies have worked with local fishing and duck hunting guide Capt. Ryan Lambert to build terraces in Quarantine Bay and adjacent Bay Denesse. The linear earthen berms act as speed bumps, slowing the water coming from the pass and allowing the sediment to more quickly deposit and form mud and sand flats. As the water shallows, vegetation takes root and marsh emerges, forming perfect habitat for migrating waterfowl and other birds, shrimp and crabs, and a host of sportfish.
It stands in stark contrast to areas just a few miles away west of the river in the Barataria Basin where there is virtually no marsh between Buras and the Gulf.
Near Neptune, locals are envisioning new names for recently formed bayous. West of the river, the names of bayous, lakes and bays have been steadily removed from maps for the last two decades. Where there were once shorelines and bayou banks there is now just open water with pilings and rip rap where camps once stood.
Growing healthy wetlands
Whether a natural diversion like Neptune Pass or dredged diversion like the planned Mid-Barataria Diversion, the results are the same. More sediment and nutrients from freshwater mean healthier, growing wetlands and, in the long run, more fisheries and wildlife production and natural protection for coastal communities.
That doesn’t mean the introduction of freshwater doesn’t come with consequences. Fish species get displaced, generally on a seasonal basis. Speckled trout don’t swim in Neptune Pass year-round. They leave in the spring when the water is cold and dirty and return in the fall when the river is low but still flowing. Oyster and brown shrimp production moves father out into basins where it was historically before the Mississippi River was confined by levees.
However, by all measurable means, the wetlands connected to the sediments and nutrients of the Mississippi River are healthier and more productive than those disconnected. That connection is what originally built those marshes and their remarkable productivity.
The Army Corps of Engineers
The rapid widening and deepening of Neptune Pass quickly became a concern for the Army Corps of Engineers. The agency, focused almost entirely on navigation and flood protection, worried the changes in river currents would lead to sandbars in the main navigation channel of the Mississippi River and even steer ocean-going ships off course. There was talk of trying to completely close Neptune in 2022 — a move that angling, hunting and wildlife advocates roundly opposed.
After weighing all options and taking into consideration the remarkable habitat-creating capacity of Neptune Pass, the Corps has recommended stabilizing the pass with rocks to try and prevent it from growing larger while still allowing water and sediment to flow through into Quarantine Bay. The land-building capacity would be further enhanced by more terraces.
Balancing the needs of navigation, flood control and the incredibly productive, but dwindling, coastal wetlands in the Mississippi River Delta is something wildlife and fisheries advocates have been demanding from the Corps for decades. Neptune Pass gives hope that those pleas are finally being heard and appreciated.
