After 57 years, new study to see if changing Atchafalaya’s flow improves swamp

 

For more than half a century, the Old River Control Structure has regulated the flows of the Mississippi and Atchafalaya rivers, preventing the all-important Mississippi from changing course.

Now, for the first time, the U.S. Army Corps of Engineers is going to team up with an environmental group to experiment with using the structure to bolster the swamps and forests surrounding the Atchafalaya.

South of Morgan City, the 1 million-acre Atchafalaya River Basingives way to Atchafalaya Bay, one of the few areas along Louisiana’s coast that is building land. However, upriver from the bay, the flow of river water and sediment has been disrupted in the basin due to changes made to accommodate ships and oil and gas pipelines.

In some cases, water flows in the wrong direction through the system, causing flooding that harms forests, according to The Nature Conservancy.

Plans for the new Atchafalaya River Project call for scientists from The Nature Conservancy to partner with the Corps to eventually test whether changes to the river’s flow could improve the basin’s health.

Currently, the Old River Control Structure is authorized to send 30% of the Mississippi River’s flow down the Atchafalaya annually, leaving some flexibility in the flow day-to-day. On a given day, the flow may be slightly above or below 30%, averaging out over the year.

Karen Gautreaux, The Nature Conservancy’s director of government relations, said scientists have long been curious about the possibility of using the Old River Control Structure for more than flood control.

“Even when there’s not a flood, it’s being managed for flood control,” said Gautreaux. “The Sustainable Rivers Partnership is asking the question: can we manage the Old River flow for nature when flood control is not needed?”

Gautreaux said the aim is to have different experimental flows mapped out and ready to test by the project’s third year. The actual testing of those flows will depend on river conditions and flood control needs.

“We think this partnership is very exciting because we’ve never been able to ask these questions before,” she said. “By asking them, we add a potential new universe of possibilities for restoration in the basin and beyond.”

Gautreaux added that the flows could send more or less water down the river and mimic the natural functions that have been broken, like trying to give habitats more time to dry out or adding more freshwater to the system.

“Whatever flow benefits the ecosystem,” she said.

Eventually, the data collected could the Corps to change the way it manages the Old River Control Structure.

“This partnership … provides an opportunity to investigate whether the structure can also help to improve the health of the Atchafalaya Basin while achieving its authorized mission,” said Mark Wingate, the Corps’ deputy district engineer in New Orleans.

The Louisiana Coastal Protection and Restoration Authority will serve in an advisory role throughout the process.

Bren Haase, the authority’s executive director, called the basin “an incredible natural, cultural, and economic resource” for the state.

“The ecological health of the Atchafalaya Basin has positive implications not just for the basin, but also for our coast,” he said.

The project is one of nine selected for the Corps’ national Sustainable Rivers Program, which aims to look at how modifying dam operations can enhance habitats while protecting communities from flooding and maintaining navigation channels.