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The Louisiana Coast: Last Call — River Diversions

NASA Earth Observatory

It’s almost impossible to find anyone in coastal Louisiana opposed to the idea of “coastal restoration.” Storms like Katrina, Gustav and Isaac have shown everyone the value of the marshes and swamps that once stood between them and the Gulf.

But when “restore” means turning things back to the way they once were, problems can arise.

The best-known example of that is the conflict over using river diversions.

“You have to be careful with the large water diversions, says Kerry St. Pé, head of the Barataria-Terrebonne National Estuary Program. He says that for his organization to support a massive water diversion, they would have to consider how big it is and how much it is.

The Atchafalaya River, yeah, it’s building marshes, building a delta; yeah, we support that fully — there’s no people living there,” St. Pé says. “It’s a fresh water river, building a delta in a fresh water area, certainly there’s no problem, let her rip.  West Bay — we support West Bay completely. West Bay, just like the Atchafalaya River it’s coming from the Mississippi River, and it’s building a small delta in a fresh water area. But when you start talking about a massive water diversion at Myrtle Grove, we cannot support that. It would drastically change the things that people depend on for their living, and more importantly, has a very, very high potential to flood people.”

River diversions would open big holes in the levees to let the river’s fresh water and sediment build wetlands the way the river once did on its own. Of course, these would be engineered projects, with lots of steel and concrete, to steer the water and sediment in the direction the engineers and planners want it to go.

The Coastal Protection and Restoration Authority’s scientific team says that, over 40 to 50 years, diversions could change the wetlands around them from the salty and brackish bays they have become over the last 70 years back to the fresh water ecosystems they were before levees disrupted that natural process.

Now, land can also be built with slurry pipelines — a method that uses dredges to mine sediment from the river bottom, mix it with a little water, and then pipe it into the sinking basins. Because it uses far less fresh water, the salinity in the marshes will stay pretty much the way it is today.

But the consensus among coastal scientists has been only diversions rebuild land affordably on a long-term basis.

Well, oystermen, shrimpers and some sports fishing guides have been fighting diversions, because changing the salinity of the water could move the species they target — brown shrimp, oysters, speckled trout and redfish — much farther south.

So they ask: Why hurt our industries and a way of life if there’s an alternative?

“What is going to happen to these two parishes?” asks Oyster fisherman and recreational fishing guide Robert Campo. “St. Bernard, Plaquemines Parish, even parts of Jefferson and Lafourche is going to feel this. Where was the economic study? Did anybody have an economist do a study on how was this going to affect these two parishes, Plaquemines and St. Bernard? Did anybody come in here and see what kind of monkey wrench this is going to throw into the cogswell cogs when they put these diversions in?”

Campo says he’s talking about a wide range of businesses affected — everything from marinas to oystermen to the shrimping business. “But it don’t stop there,” he says. “This is going to affect the insurance businesses. How is this going to affect the insurance business? Well, when I can’t pay my bills I’m definitely not paying for insurance.”

“Is it going to injure the fisheries? No, I don’t think it is," says Garret Graves, head of the state's Coastal Protection and Restoration Authority. “I think that what happens — from the studies that we’ve seen and from the projects we have out there now for fresh water diversions — is that it does move the fisheries. In the case of things like oysters, which is a static species — they don’t swim, they don’t move — it’s an important component of this to ensure that we get ahead of these diversion projects, and work with the leaseholders to move these oyster leases to areas that will be within the right salinity levels. But it boils down to a scenario where you either move these oyster reefs or you move your people.”

Credit USGS
The top photo was taken after Hurricane Gustav on the west side of Bayou Terre aux Boeufs, which is in the outflow of the Caernarvon Diversion. The bottom photo was taken on the east side of the bayou, which is largely blocked from Caernarvon's fresh water. USGS researcher Chris Swarzenski said the images demonstrate the weakness of the soil caused by the nutrients in the river water.

There are some credible scientists who disagree with their colleagues on diversions. Recent research has shown the fertilizer-based pollutants carried in today’s river can kill marsh plants and lead to a rapid deterioration of the wetlands soil base.

These scientists understand the state’s sense of urgency to do something big, and do it now. But they urge caution.

Chief among those is Gene Turner, a distinguished coastal scientist at LSU.

“The Master Plan has a list of the anticipated land gain from all those diversions," says Turner. “Now, I want to frame that: that total gain is 23 times higher than the history of land gain for 7000 years on this coast.

"Let me say that another way: the land gain over 7000 years has been on the order of a square mile, square mile and a half per year. All those diversions are supposed to — if they’re successful over 50 years — it’s going to bring in 23, 25 times more land than we had for the whole coast for 7000 years."

Turner says that’s for half the river, which means it will actually be on the order of 50 times more effective than nature has been for 7000 years. He says the diversions are also not mimicking nature, per se, since they'll be created by a hole in a levee — the natural system was an overbank flooded for the whole length of the levee.

"So we’re using a less than natural way to bring water overbank, and we don’t have good examples of where it’s worked," he says. "In fact, we have examples where they’ve been harmful, and they’re way above what the natural system has done for 7000 years. So, I think that’s cause for some pause.

“At this point that doesn’t seem likely to happen. The coastal restoration community from the CPRA to a list of environment groups are all working hard to get funding from Congress and the Deepwater Horizon spill to fund these big projects,” he says.

Slurry pipelines will be used — in fact, they are already being used. But the community driving this effort keeps looking in the rear view mirror, and they see a monster approaching.

“The diversions are absolutely fundamental,” says Graves. “You can do things like this mechanized dredging and pumping sediments out of the river like Bayou Dupont, but when you look at the cost of projects like that as compared to the benefits of them, you get a major return of investment — in fact, about four times the return on investment, or more — from doing  diversion projects as compared to marsh creation or restoration-type projects.”

So far, the state Legislature has agreed unanimously. It’s a pretty good bet at this time that river diversions are coming — as soon as the state gets the money to build them.


Support for The Louisiana Coast: Last Call comes from the Greater New Orleans Foundation, an organization that addresses the challenges facing people who live and work in the coastal communities of Southeast Louisiana.

The Louisiana Coast: Last Call is written and reported by Bob Marshall of The Lens, and produced by Fred Kasten.

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