‘Accidental’ rebuilding of Wax Lake Delta shows promise of diversion projects

Take a boat ride down the Gulf Intracoastal Waterway, hang a right at Mallard Pass and you’re heading into an area of south Louisiana that’s seen consistent coastal marsh growth during the past several decades.

The landscape of waterway-lined willow trees gradually gives way to fields of American water lilies and then to marsh grass and finally to large expanses of mud flats the farther south you travel into the Wax Lake Delta.

It’s a healthy delta created by accident when the U.S. Army Corps of Engineers, in an effort to provide flood protection for Morgan City, dredged a straight line channel from the Atchafalaya River southward as a secondary way to discharge river flow to the Gulf of Mexico.

Then in the 1970s, flooding on the Atchafalaya River via the Mississippi River sent loads of sediment down the channel, bringing to the surface for the first time mud flats that had been building under water for decades.

The sediment that built the delta took a long trip: starting at the Mississippi River, diverted down the Atchafalaya River and through the basin, carried down to the Gulf Intracoastal Waterway and then farther south into the growing delta.

“If we tried to propose a sediment diversion like this, they would say we’re crazy,” said Paul Kemp, coastal oceanographer and geologist at LSU.

“This is a very healthy delta here,” he said of the Wax Lake Delta. “This is about as good as it gets.”

It was to this place that activists, researchers, government officials and reporters travelled Tuesday in part to showcase the good effect diversions from the state’s two major rivers can have on the landscape.

The state is currently planning a number of diversions along the Mississippi River to help bring sediment into rapidly eroding wetlands.

“If this can happen on accident, what are the possibilities that we can plan and thoughtfully design one like it,” said Bren Haase, assistant administrator with the planning and research division of the state Coastal Protection and Restoration Authority.

The diversion furthest along in the planning process is the one proposed at Myrtle Grove in Plaquemines Parish and envisioned to include a water control structure through the levee that would send sediment into the marsh and open water areas west of the parish.

Wax Lake Outlet and the Myrtle Grove location would be different in that the outlet runs all the time and can carry 150,000 cubic feet per second at non-record flows while the Myrtle Grove location would likely operate only at specific times and is being planned for maximum 75,000 cfs. However, Haase said, the goal is to operate the Myrtle Grove structure for the sole purpose of building land.

Plans for the Myrtle Grove diversion have raised concerns from fishermen and others about negative impacts a large diversion could have on an area known for its fishery resources. Although the state is still investigating possible fishery impacts, lessons from Wax Lake Outlet show that, at least in this case, fisheries weren’t destroyed.

“Maybe we’re not going to catch speckled trout right here, but if we don’t do diversions we won’t catch them anywhere,” Haase said.

Ivy St. Romain, owner of Ivy’s Tackle Box and Marine Supplies as well as Blue Rebel Charters, said not only has the diversion of freshwater down the Wax Lake Outlet not hurt fisheries, fishing has picked up in the area.

“We’ll catch red fish right next to bass,” he said.

The only fishery that has changed is the oysters, which need saltier water at certain times of their life cycle.

Also, the additional land is helping in other ways, he said.

“When we get a strong (storm) surge, it really slows everything down,” St. Romain said. “It really protects us a lot.”

Another argument against large diversions is that there’s not enough sediment in the Mississippi River to build the land needed to keep up with coastal land loss.

“All I can say is look around you,” Haase said.

And there was another message from Tuesday’s tour.

People keep hearing about coastal land loss and communities becoming more vulnerable to the Gulf of Mexico, but the good news is that action is possible, said Simone Maloz, executive director of the coastal Louisiana group Restore or Retreat.

Not doing diversions, she warns, will lead to more bad news.

When her organization formed in 2000, the “retreat” portion of the name was seen as a threat. Since then, that word has become a reality in areas like Terrebonne Parish.

“No one buys a house down the bayou. They buy them for camps,” she said, and some people have lost hope that something can be done.

Looking out over the Wax Lake Delta, she said, “there’s hope out there.”

Follow Amy Wold on Twitter, @awold10.