Louisiana’s Coastal Marshes Make Liars Out of GPS.

Dramatic land loss over the last century is to blame. Where the standard issue GPS map shows green or yellow land masses with bayous and bays coursing through, in reality there are wide-open expanses of water from subsidence and erosion that have robbed the state nicknamed “Sportsman’s Paradise” of nearly 2000 square miles of prime fish and wildlife habitat since the 1930s.

There are two areas, however, where the GPS has the opposite problem. Where there was once a wide-open shallow bay from the bottom end of the Atchafalaya Basin to the Gulf of Mexico, there is land stretching across the horizon.

Right in the middle of Louisiana’s coast, separating the Mississippi River Delta to the east from the Chenier Plain to the west are the Atchafalaya River and Wax Lake deltas, the only two actively building coastal deltas in North America.

Where most Louisianans are used to seeing coastal marshes in various states of decline and collapse with land vanishing from one fishing trip to the next, the Atchafalaya and Wax Lake deltas are ever-growing, with new mud flats, sand bars, islands and grass beds forming with each spring sediment slug coming from the Mississippi River.

Along the Mississippi below New Orleans, which is hemmed in by levees and jetties, once-popular fishing destinations like Yellow Cotton Bay and Hospital Bay have been removed from the latest maps. At Wax Lake however, map makers are naming new islands that didn’t exist a decade ago.

The Atchafalaya River is the Mississippi’s largest remaining relief valve, draining 30 percent of the combined flows of the Mississippi and Red River through the Atchafalaya Basin, America’s largest river-basin swamp. The Atchafalaya Delta is growing just like a river delta should, like the Mississippi River’s delta was in the early 20^th century before flood-control levees and navigation-aiding jetties were built to prohibit the annual flooding and sediment deposits that built Louisiana’s coast over millennia.

The Wax Lake Delta is more of an accident. The man-made canal that birthed the delta was constructed in the early 1940s to help bleed off waters from the Atchafalaya River and protect Morgan City and other coastal towns from riverine flooding. Few paid attention or cared that sediments being carried by that channel were being deposited at the outlet’s mouth in Atchafalaya Bay.

Those deposits went unnoticed until 1973 when a historic flood threatened to undermine and over-top flood-control structures throughout the Mississippi River basin. When the flood waters receded, new land had emerged above the water’s surface at the mouth of Wax Lake Outlet. More land has emerged nearly every year since. Even after the delta’s grasses were burned and its sediments shifted by storm surges from Hurricanes Katrina, Rita, Gustav and Ike, the Wax Lake Delta recovered and expanded the following spring.  Since 1973, the islands, tidal flats, grass beds and splitting channels have grown to cover about 40 square miles, all public lands managed by the Louisiana Department of Wildlife and Fisheries.

The accident at Wax Lake has given coastal restoration advocates and state and federal agencies a template for how to attempt to stop the loss of the Mississippi River Delta and, maybe, eventually begin replacing the wetlands lost. The question is, can the land-building capabilities at Wax Lake be replicated with the kinds of controlled diversions of water and sediment state coastal planners envision for the collapsing marshes east and west of the lower Mississippi?

That and many other questions like potential impacts to fisheries and coastal communities are being pondered and examined by a group of biologists, economists, ecologists and geographers called the Expert Panel on Diversion Implementation and Planning organized by the recently-established Water Institute of the Gulf.

The panel’s members, state and federal officials and a host of representatives from conservation groups toured the Wax Lake Delta in late October, greeted by ducks, bald eagles and a host of other birds and higher-than-normal water levels that were still moving sediment. While the question of saltwater fisheries impacts, both positive and negative, went largely unanswered during discussions of what was seen, there was little denying the group was impressed by the quality of the habitat.

The Wax Lake Delta may not be the ideal example of what’s to come if state coastal officials and scientists can weave the seemingly endless slalom of policies and political oppositions to projects that promise large-scale change. The Wax Lake Outlet is an uncontrolled diversion. Its waters added to that of the nearby Atchafalaya Delta mean the habitat is generally more suited for waterfowl, alligators and largemouth bass with occasional visits from speckled trout and redfish. The sediment and water diversions along the Mississippi will have gates that can be opened only when the river has the greatest land-building capacity while allowing brackish-seeking species like trout and redfish and even bass and ducks to thrive when water and sediment loads drop and the gates are closed.

The Wax Lake Outlet can move as much as 250,000 cubic feet of water per second at peak flood. The diversions will likely move far less than half that amount.

While it may not be a one-to-one comparison, what’s happening at Wax Lake has given coastal planners a glimpse of what is possible when a river’s delta is given back its river. If Louisiana’s coastal wetlands, vital to fisheries production across the Gulf of Mexico, are to have any chance at long-term sustainability the sediment from the Mississippi River flowing freely into the Wax Lake Delta must flow again in the Mississippi River’s Delta as well.

The Theodore Roosevelt Conservation Partnership has worked extensively with recreational fishermen, policy makers and scientists across the Gulf to identify and advance a host of habitat restoration efforts including sediment diversions along the lower Mississippi River. For more information about our efforts, please check out our website at www.trcp.org.