Scientists see promise in ‘pulsing’ river diversion. State coastal czar says ‘It ain’t gonna work’

Wetlands in the Wax Lake Delta, one of the few places along Louisiana’s coast where land is growing instead of being lost. The science conducted at Wax Lake informed coastal restoration projects such as the now canceled Mid-Barataria Sediment Diversion project. (Elise Plunk/Louisiana Illuminator)

One of the key scientists involved in a now-defunct plan to rebuild coastal wetlands in southeast Louisiana has a new approach for how to take on the task. 

Ehab Meselhe, a coastal restoration scientist and professor at Tulane University, is researching a new way to operate the Mid-Barataria Sediment Diversion he says could be a compromise to move the project forward. But whether officials who control coastal restoration are willing to accept his idea is more uncertain than the science behind it.

The concept uses the bones of the previous large-scale sediment diversion, mimicking the natural processes that originally created the delta region at the mouth of the Mississippi River. The power of the river’s current slowly feeds layers of sediment to build new marshland along Louisiana’s coast.

But instead of keeping the flow of water constant, Meselhe is exploring a way to periodically turn off the faucet.

 His research has yet to be published, meaning it hasn’t undergone academic scrutiny. But it does draw from previous bodies of knowledge.  

“We started to think about exploring the concept of pulsing,” Meselhe said, along with piling dredged sand by the mouth of the floodgate that controls flow from the Mississippi River. When opened, the sediment and sand would be carried into Barataria Bay, helping build land in coastal Jefferson, Lafourche and Plaquemines parishes.

His idea would likely involve less of the river’s flow from the original plans, which Meselhe said would result in less land being built but far less dilution in the salinity of the bay’s water. The chief complaint among opponents of the diversion is its potential impact on the estuary, its sealife and the livelihoods it supports. Oyster farmers, in particular, have said their beds in the area would perish.  

Meselhe’s idea combines the pulsing concept with the idea to transport dredge material into the outflow area, which draws off previous scientific experiments to create sand or mud “engines.” 

A plusing diversion has been studied before, said Sam Bentley, professor and chair of LSU’s geology and geophysics department, as well as co-director of the coastal restoration research group MissDelta Consortium. 

The Netherlands and river systems in southeast Asia have used the sand engine concept successfully, Bentley said, but Meselhe’s plan would combine elements in a brand new fashion in North America. 

“The idea of engineering shorelines so that sediment is redistributed naturally by existing currents is something that’s been around for several decades,” Bentley said, “But Ehab’s design concept is unique, it’s exciting … and I think has great potential.”

The state official in charge of coastal restoration says “it ain’t gonna work.”

“Hats off to everyone who has an idea,” said Gordon “Gordy” Dove, chairman of the Louisiana Coastal Restoration and Protection Authority.  While explaining that he doesn’t mean to be “patronizing,” he said he doesn’t believe in further experimentation over traditional restoration land-building methods such as “dredging, dredging, dredging” or a smaller-scale diversion higher up in the basin. 

“My job is to protect the coast, and we don’t have much time. That’s why I believe in trying what’s worked in the past,” Dove said. 

Meselhe, Bentley and other scientists say dredging alone won’t be the solution Louisiana’s coast needs. 

“I think that we are at an inflection point in time right now where we have to find new solutions. We can’t rely on conventional engineering, you know, old old school solutions,” Bentley said, adding that dredging could be done in conjunction with other methods.

Scientists also see problems with relying only on a small-scale diversion for the Barataria Basin, saying it will still pour considerable freshwater into the bay. Meselhe’s computer models of different diversion projects in the region show that — even with much less water moving than the 75,000 cubic feet per second that Mid-Barataria called for — they still push salt water further away from the shore. 

“Whether it’s Mid-Breton or Mid-Barataria, or even some of the work that we have done on Caernarvon and Davis Pond, salinity has always been a challenge,” Meselhe said. 

“Unfortunately, changing the salinities within the basin doesn’t require that much fresh water input. It can really change pretty easily,” said Alisha Renfro, a coastal scientist with the National Wildlife Federation.

James Karst, communications director for the Coalition to Restore Coastal Louisiana, said he thinks an idea like Meselhe’s could bode well for a compromise. 

“Clearly, Mid-Barataria is no longer, and yet the crisis still exists,” Karst said. “We need to do something, and we need to do something urgently. It has to be something big.”

Some critics of the Mid-Barataria Sediment Diversion are open to Meselhe’s alternative. 

Mitch Jurisich, chairman of Louisiana’s Oyster Task Force, said if the research proves to be fruitful, he thinks the oyster industry will rally around a compromise. 

“We want to see land building,” he said. “Fresh water diversions can be used very beneficially to not only enhance the environment but to help the fisheries, if controlled.”

But even if enough people agree Meselhe’s idea has merit, there could be problems with moving it from theory into reality. 

“How feasible is it really to do that?” Renfro said. “What’s going to be the cost of the dredging and augmenting, like putting sediment into the diversion channel? Is that going to be a cost that increases over time?” 

Cost and promptness are critical, experts said. Meselhe’s previous research shows that, as more time passes, it will be harder to rebuild land within the Barataria Basin. 

“I am hoping that, because we are building on a concept that has been thoroughly reviewed, we can cut down on the time,” Meselhe said. “But I don’t know, does that mean months, or does it mean years? I don’t know, but I’m hoping that it’s not 10 years.”

“It’s totally within the realm of feasibility,” Bentley said. “You just have to get the right people at the table to do it, including state and federal government.”

“Not doing any restoration in the area is not an option,” Renfro said. “It comes down to funding, and it comes down to political will to actually restore the coast in a way that addresses the scale of land loss that we have.”

Jurisich believes that with more community engagement, compromise is possible for river diversions, even with tensions still high after fighting for so long over the original Mid-Barataria plans. 

“It doesn’t have to be one side or the other,” he said. “I think they should be engaging with communities, talking with the fishermen, especially generational fishermen” more than what officials did for the original diversion proposal. 

Meselhe said that while his research is still in its infancy, the early results are promising.

“There is nothing that you can implement in the landscape that has zero impacts, zero negative impact. That doesn’t exist. So we have to come to grips with that,” Meselhe said. “But if the negative impacts are a lot smaller, perhaps it can be palatable to the local communities and to the fishing community and to the parish residents.”

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