Restoring Nature at Loch Leven
The Nature Conservancy plays a key role in the largest floodplain reconnection project in the Lower Mississippi.
Ever since humans first sought to control the Mississippi River, success has come at an ecological cost. Protecting human communities from floods and maintaining the river as a transportation artery meant disconnecting it from its floodplain, often with bad results for the plants and animals that depend on it. In Wilkinson County, Mississippi, an ambitious ongoing restoration effort on a 6,000-acre river island is showing the good things that can happen when river and floodplain are reconnected.
Led by The Nature Conservancy, a partnership including a dozen other conservation groups, government agencies, universities and private companies has reconnected Loch Leven Island, long cut off by a 12-foot ring levee, to the Mississippi’s natural flood pulse.
Thanks to a marriage of nature and human engineering, an area that had seen increasingly damaging floods, degraded bottomland hardwood forest, and dwindling diversity of plant and wildlife species now has resurgence in fish and wildlife populations and the bottomland hardwood forested wetlands are recovering.
Scott Lemmons, The Nature Conservancy's state director in Mississippi, has overseen the Loch Leven project since 2016. That’s when the owner, weary of repeated flooding that periodically turned the island into a giant bowl of water 12-foot deep with no drain plug, reached out to TNC for help. The solution? A box culvert, cutting through the levee and running through the island, allowing water to flow on and off gradually as the river level rises and falls.
It could become a model for problem spots up and downriver.
“From TNC's perspective, we’re looking for floodplain reconnection projects such as this for improved water quality,” Lemmons said. “There are wildlife habitat benefits for fish migration, spawning opportunities, migratory waterfowl, bottomland hardwood forest health – there’s a multitude of conservation benefits, including flood storage capacity. The key is keeping the water on the landscape.”
Loch Leven was created in 1776, when the river changed course, creating a new oxbow surrounding 6,000 acres. The ring levee was built in the mid-19th century to make the island farmable. That worked well enough for more than a century, but time, development and climate change brought new challenges. Stronger levees upstream, combined with more-frequent flooding, send higher, faster-moving water volumes downstream. As the waters bypass the floodplain, more nutrient rich sediment from farmlands upstream have nowhere to go but into the Gulf of Mexico, contributing to the oxygen-deprived hypoxic or “dead zone” that develops there every summer.
For Loch Leven, floods overtopping the ring levee were catastrophic. Each time, the instant inundation trapped thousands of deer and other wildlife that were unable to swim the miles suddenly required to reach dry land. Prolonged standing water smothered the bottomland hardwoods, threatening the food source for countless wildlife species.
Restoring Loch Leven as floodplain has many ecological benefits, but none more remarkable than for migratory fish species. Bryan Piazza, TNC's Director of Freshwater and Marine Science in Louisiana, points to the alligator gar, a species that had seen steep decline in recent decades with the loss of its floodplain spawning habitat.
“Some people call the gar a trash fish,” Piazza said of the giant, prehistoric-looking creatures “but study after study has shown that if the habitat is right for gar to get on that floodplain, the habitat’s right for everything else that needs that floodplain.”
Since the Loch Leven restoration, scientists from Nicholls State University in Thibodaux, have documented 28 species of young of the year fish there, indicating that they’re spawning in the floodplain.
TNC has installed a state-of-the-art monitoring system that will use a satellite to determine how much nitrate is being removed from the water.
“We're testing whether we can monitor fertilizer runoff, the nitrate that comes from fertilizer runoff from agriculture and comes down the river, goes out to the Gulf of Mexico and makes the dead zone,” said Bryan Piazza.
Floodplain projects like Loch Leven, remove nitrate from the water, and it is estimated that these floodplains can remove about 40% of the nitrate that comes into them. So, the water has at least 40 % or more less nitrate when it leaves the Loch Leven floodplain.
He adds, “Usually, we monitor nitrate with probes that are in the water that must be downloaded, they must be cleaned. We are now using optical sensing technology. Every time satellites pass over and take a signature picture of this area right here, we can estimate what the nitrate is at this point on the ground from a satellite."
When the culverts are closed, allowing Loch Leven to fill temporarily to its full full depth, the levee holds back 72,000 acre-feet of water for gradual release, alleviating potential flood damage downstream. While the water is impounded, metric tons of sediment fall to the bottom of the basin. When water is later released gradually, it’s largely clear. Piazza figures one prolonged flood in 2019 kept the equivalent of more than 1.2 million truckloads of sediment from washing into the Gulf.
Champions of Loch Leven, including U.S. Sen. Roger Wicker of Mississippi, credit collaboration with making it happen, said Brad Ferguson, Wicker’s State Field Director, “It’s a great partnership between private nonprofits, landowners, private industry, our government both federal and stateside, the Corps of Engineers and U.S. Department of Agriculture and others, all coming together.
“Tens of billions of dollars (in commerce) flow up and down this river annually and it’s vitally important to keep this channel open, while also protecting life and property and enhancing wildlife habitat.”
For Loch Leven owner Erik Piazza (no relation to Bryan), the broad partnership was a unique opportunity. “TNC has been wonderful to work with,” he said. “They and their partners have been able to provide resources and funding that we would never have been able to provide on our own.”
Lemmons still marvels at what the Loch Leven reconnection has achieved but recognizes that the Mississippi needs many more projects just like it, up- and downstream. “You can’t just do it on the lower river,” he said. “You have to start on the Missouri in the Midwest. It has to start on the Ohio, the Tennessee. The Mississippi River basin encompasses 32 states and two Canadian provinces. It’s the fourth-largest drainage basin on the planet and we need a basin-wide approach.”
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