Atchafalaya Flow Change Proposed

By Richard Burgess
Jul 5, 2009; The Advocate

A mass of concrete and floodgates near the head of the Atchafalaya River acts as a faucet of sorts to control how much water flows out of the Mississippi River into the vast Atchafalaya Basin swamp.

The U.S. Army Corps of Engineers has kept a careful hand on that faucet for fear the larger Mississippi River might change course down the Atchafalaya.

After resisting years of calls from farmers, crawfishermen and conservationists for more or less water — depending on who is asking and when — the corps is considering the possibility of change.

The impetus is the idea that the colossal load of sediment flowing down the Mississippi and Atchafalaya rivers could play a key role in rebuilding the state’s shrinking coast.

“There might be an opportunity to maximize the effect of those two river systems,” said Nancy Powell, chief of the corps’ New Orleans district hydraulics and hydrologic branch. “It’s kind of exciting.”

Powell keeps  a watchful eye on the corps’ Old River Control Structure near Simmesport, where the federal agency raises and lowers giant gates to regulate how much of the Mississippi River is allowed to flow into the Atchafalaya.

The Atchafalaya is fed by the Red and Mississippi rivers, and if the relationship were not managed, there is little doubt the Mississippi would choose to take the route of the Atchafalaya, which offers a shorter path to the Gulf of Mexico.

The corps operates under a 1950s congressional mandate that only 30 percent of the Red and Mississippi rivers should flow into the Atchafalaya — freezing in time the distribution that existed at mid-century.

The ability to regulate water flowing into the Atchafalaya Basin has led to repeated calls that the corps wield that power for reasons other than keeping the Mississippi in check.

“You have a control system in place to manage it, but you are not managing it,” said Paul Kemp, vice president of the National Audubon Society’s Gulf Coast Initiative. “We see it as a place to achieve big ecological improvements very quickly with minor water changes.”

The corps has agreed only a handful of times to increase the flow into the Basin.

“Those have been what we consider short term, small-scale changes,” Powell said.

She said what the corps is now researching is the possibility of larger, long-term alterations.

The driving interest is coastal restoration.

Louisiana’s current coastal plan rests heavily on using the sediment-laden water of the Mississippi and Atchafalaya rivers to rebuild land.

The idea is to open up levees or build large pipelines to spread the water around, recreating how the rivers would have built land centuries ago when freely meandering back and forth along the coast.

While a recent LSU study questions whether the Mississippi carries enough sediment to stave off massive land loss, the concept of using the river as a tool remains attractive to many coastal restoration experts.

The Old River Control Structure could play a critical role in that effort because it controls not just the water, but the massive load of sediment the water carries.

Kemp said not using the Old River Control Structure as a tool in directing sediment to the coast is like “doing coastal restoration with one hand tied behind our back.”

“Is it possible that the management of the Atchafalaya can be incorporated into the whole coastal program?” Kemp said.

The biggest question is whether the corps could keep the Mississippi from changing course should more water flow down the Atchafalaya, or keep the structure from failing while holding back more of the Mississippi.

“Can we change the split and still have that stability? That has yet to be determined,” Powell said.

Complicating the issue is damage that part of Old River Control Structure suffered during flooding in the 1970s, which limits how much of the Mississippi can be held back.

“So we need to be careful how we allocate water,” Powell said.

Beyond the questions about the stability of the rivers and the control structure, there are concerns about what effect altering the Mississippi-Atchafalaya split would have on everything downstream. Those issues include the flooding of communities, the impact of changes on other waterways that depend on river diversions and the maintenance of navigation channels on both rivers.

Some conservationists also hope that any changes at the Old River Control Structure would take into account the needs of the Atchafalaya Basin, the vast swamp that stretches along the river from Simmesport down the Gulf of Mexico.

“There is a lot of sense that it could be managed better,” Kemp said. “There is not a lot of agreement on how that should be done.”

The competing interests are many.

Recreational fishermen often want to keep water up to allow for boat access, while farmers might want less to keep fields dry.

And some natural processes, such as the development of cypress forests, depend on a natural cycle of flooding and drying out.

“They (cypress) don’t regenerate anymore because it is always flooded,” said Paul Davidson, director of the Black Bear Conservation Coalition, a nonprofit group that has worked to conserve and expand habitat for the threatened species.

Davidson said he would like to see more of a focus on mimicking the natural flooding cycle of the swamp.

“I personally have advocated trying to get closer to the historical hydrology of that system,” he said.

The natural flooding cycle is also critical for the Basin crawfish crop.

The few times the corps has put more water into the Atchafalaya for reasons other than flood control have been to raise water levels in the spring to aid the crawfish crop during an unusually dry year.

“In other words, when you don’t have a good spring flood, you create one,” said Louisiana Wildlife Federation Director Randy Lanctot.

But putting more water into the Basin, whether for coastal restoration or a controlled spring flood, could deposit sediment in areas of the swamp that are already rapidly filling in with dirt, he noted.

“It’s the distribution of sediment. The resource is direly need in some areas and not needed in others,” he said.

Reconciling all the concerns and issues might be made easier with work being undertaken by the state’s Atchafalaya Basin Program and The Nature Conservancy.

The two groups signed an agreement earlier this year to collaborate on issues in the Basin.
The Nature Conservancy has just begun a year-long process to synthesize the volumes of past research on the Basin to help guide future management decisions.

“It’s been fairly disconnected. Nobody has put all that together,” said The Nature Conservancy’s Louisiana director, Keith Ouchley.

A related project by the state Atchafalaya Basin Program’s Technical Advisory Group is pulling together data on the Basin that is scattered in the files of various federal and state agencies.
That information will be used to evaluate different proposals in the Basin, said state Wildlife and Fisheries biologist Mike Wood, who chairs the Basin advisory group.

“The Basin is terribly complex. Any water fluctuation will affect all manner of aquatic vegetation, fishing interests, oil and gas operations, and on and on,” Wood said. “Without a tool or someway to analyze the data, it’s a guessing game.