Nikki Buskey / Houma Courier
HOUMA — From space, the land-building power of this year's river flood is obvious. Satellite images show plumes of delta-spawning sediment pouring from the mouth of the Atchafalaya River, the Mississippi River and the Bonnet Carre spillway.
But a skeletal-looking no-man's land sits in the middle of the state, absent the plumes obvious elsewhere.
“The real tragedy of this flood is that it isn't getting sediment to some of these areas that sorely need it,” said Phillip Turnipseed, director of the U.S. Geological Survey's National Wetlands Research Center, which published the satellite photos of the flood. “Terrebonne, Lafourche, Barataria, the Breton Sound — you're all being left out.”
River sediment built much of coastal Louisiana. Cutting off communities, like Terrebonne and Lafourche, from the river caused the coast to rapidly sink and erode into the Gulf.
Today the rivers are moving as much as 3.4 million cubic feet of water and sediment past the eroding coast and into the Gulf of Mexico. A re-plumbing of the system is required to get the river sediment to areas that need it, scientists say.
THE DELTA NEXT DOOR
Throughout the 20th century, the Atchafalaya River has captured more flow from the Mississippi River and carried more sediment into the Atchafalaya Basin.
The Old River Control Structure was built in 1963 to stabilize the Mississippi and prevent it from shifting its flow to the Atchafalaya, bypassing and financially devastating New Orleans ports.
Just 30 percent of the river's flow is allowed down the Atchafalaya today, but the river still builds, filling in lakes and bays and causing navigation headaches in Morgan City, where crews struggle to keep canals and bayous open.
During the 1973 flood, so much sediment poured down the river that new deltas — like the Wax Lake Outlet and Atchafalaya Delta — emerged. They've grown every year since.
Over the past 78 years, the Atchafalaya Basin has gained more than 30 square miles of land, the most of any basin in Louisiana, according to the U.S. Geological Survey.
But little of that sediment reaches Terrebonne or Lafourche.
“Some land will be built in some places during this flood. The question is where will get it where we want it to be?” said Alex Kolker, a researcher at the Louisiana Universities Marine Consortium.
WILL IT COME HERE?
Kolker aims to measure freshwater and river sediment from this year's Atchafalaya River flood. He put monitors in Terrebonne wetlands immediately before the Morganza Spillway was opened last month with the intent of measuring how much makes its way to lower Terrebonne.
“A lot of people think bringing in the river is the way to restore the coast, and we want to quantify that,” Kolker said.
Mitch Marmande, an engineer at T. Baker Smith in Houma, said a barge submerged in Bayou Chene to keep floodwaters from reaching Terrebonne rerouted river water, normally bound for the Gulf Intracoastal Waterway, into Lake Penchant.
“The marshes will be flooded with some nice muddy water,” said Denise Reed, a wetlands ecologist with the University of New Orleans.
But those wetlands are already Terrebonne's healthiest, Marmande said, and it's unlikely “you'll see the same land-building effects.”
The Atchafalaya's freshwater influence is likely to stop at the Houma Navigation Canal, which acts as a barrier, Marmande said.
Brady Couvillion, a geographer with the agency's National Wetlands Research Center, said this year's flood is likely to build land in the Atchafalaya delta, but much of the sediment will pour into and fill Atchafalaya Bay, and limited amounts will make it into Terrebonne. Once that sediment reaches the Gulf, it is pulled west by currents, Couvillion said.
“The real story is where the sediment is not getting,” Couvillion said. “The majority of that sediment goes where we're telling it to go. And we're not telling it to go into Terrebonne marshes.”
RESTORATION, NOT FLOODING
Many scientists say restoring the river flow that built Terrebonne and Lafourche is needed to help stop coastal-wetlands loss. Without the river's freshwater and sediments, coastal communities will continue to sink and wetlands will disappear.
But how do you restore something cut off decades ago?
Terrebonne Parish officials have worked for more than two years on a project that would pump Morgan City sediment here.
River sediment is a $20 million-a-year problem in St. Mary Parish, where dredging must constantly keep pace with the land-building Atchafalaya River and its attempts to clog navigation canals with dirt.
In Terrebonne, that same river sediment could build wetlands and solve a “priceless” problem, said South Lafourche Levee Director Windell Curole, a member of the state's Coastal Protection and Restoration Authority.
The project would use a pipeline to pump sediment from Morgan City to western Terrebonne, a distance of about 20 miles.
Terrebonne Coastal Restoration Director Nick Matherne said the parish needs $1.5 million in state money for engineering and design work.
The plan is doable, officials said, as Atchafalaya River water is regularly funneled through Bayou Chene and the Gulf Intracoastal Waterway into Terrebonne and Lafourche parishes.
The path was blocked by the sinking of the barge, an act intended to keep floodwaters out of Terrebonne.
It was successful, but it also kept out the freshwater, said Denise Reed, a wetlands ecologist with the University of New Orleans.
Multiple agencies have looked at using the Gulf Intracoastal Waterway as a conduit for freshwater. It delivers freshwater through Minors Canal, the Houma Navigation Canal and Company Canal into various parts of Terrebonne.
“The challenge is to make the most of it for restoration, but not get water into people's houses,” Reed said. “Hopefully we can work that out in the future.”