Mississippi River spillways have kept Louisiana dry and safe. That may no longer be enough

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Beside the murky waters off Pass Christian, shrimp boats docked in the distance, David Gautier is worried about a threat many miles away that he cannot control.

Gautier, 64, runs a seafood business on the waterfront of this historic town along the Mississippi Gulf Coast. But his concern has less to do with his home state than with neighboring Louisiana — or, more precisely, the flow of the water from the mighty river that runs through it.

“We don’t control that Mississippi River,” says the owner of Gautier’s At The Harbor. He adds later: “If it’s not managed correctly, it can be catastrophic.”

Gautier went years without oysters and only recently began to emerge from that hit to his business. The reason? They were killed off in 2019, the result of high Mississippi River water diverted through the Bonnet Carre Spillway near New Orleans.

The freshwater and nutrient pollution that eventually inundated the Mississippi Sound wreaked havoc on the region’s ecosystem and tourism industry. It is a dilemma that is only expected to worsen in the decades ahead due to projections showing more extreme weather, and its implications range far beyond the Mississippi Coast.

A series of giant safety valves along the Mississippi River have helped protect the New Orleans area from catastrophic flooding for nearly a century. But now there’s a problem — several of them, in fact, and they’re converging all at once.

The Mississippi Gulf Coast’s protests over the use of one of those valves, the Bonnet Carre Spillway, have grown louder and led to lawsuits, particularly after record openings in 2019. The Morganza Spillway on the opposite side of the river has been rarely used, but opening it more frequently draws concern from landowners, residents and port operations in its path.

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Mississippi officials are careful to stress that they do not want New Orleans or anywhere else to flood. But they say solutions can be found, and the burden can be shared.

“This is a national problem, and it calls for a national solution,” said Gerald Blessey, the former mayor of Biloxi now helping lead a coalition seeking to draw greater attention to the issue.

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The need for a reliable shipping channel, as well as the obligation to protect cities from flooding, has created a largely manmade system of managing the Mississippi, and any change to it can reverberate elsewhere.

The current system is now nearly a century old, and it has worked largely as designed. Built in the wake of the epochal 1927 Mississippi River flood, the modern network of levees, floodwalls and spillways has prevented the lower river from breaking its banks and allowed shipping to flourish, including for grain exports from the country’s Midwest to ports around the world.

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The Bonnet Carre has in particular been vital to south Louisiana. To keep the river from rising above 1.25 million cubic feet per second — or more than 550 million gallons every minute — the Corps opens it.

It is a surprisingly analog process, with cranes removing wooden beams — or “needles” — set across 350 bays to allow river water to gush through. The number of bays opened depends upon the amount of water that must be diverted.

The water then tumbles through the spillway itself, guided by levees through a channel for nearly 6 miles to Lake Pontchartrain. It eventually reaches the Rigolets, the Mississippi Sound and the Gulf.

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For the first decades of the spillway’s existence, that prediction proved roughly accurate, though, as always, with lots of variation in weather patterns. Bonnet Carre was opened eight times between the completion of construction in the 1930s and the end of the century.

But since 2000, it has been opened seven times, and it looked as if it would again be necessary earlier this year. In the end, it remained closed thanks to river levels remaining just below the trigger.

The Corps had come under heavy pressure from Mississippi officials to use Morganza before opening Bonnet Carre. That did not happen, but, farther upriver, the flow of water diverted from the Mississippi River through the Old River Control complex to the Atchafalaya jumped significantly around that time, records show.

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The record 2019 openings were the last straw for Mississippi. For the first time, Bonnet Carre had to be opened twice in a year, for a total of 123 days. An estimated 10 trillion gallons rushed through it.

The muddy, brown water drained from parts of 31 states and two Canadian provinces brought with it harmful algae blooms and nutrient pollution. That was amplified by increased flow from the Pearl and Pascagoula rivers.

The result was a federally declared fisheries disaster in Louisiana, Mississippi and Alabama.

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Mississippi communities filed two separate lawsuits against the Corps in the flood’s wake. One was dismissed, and the other resulted in only a partial victory, requiring the Corps to consult with federal fisheries officials on Bonnet Carre openings.

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The Morganza Spillway could be considered a sibling of Bonnet Carre. Located farther upstream at the town of Morganza, not far from the Louisiana State Penitentiary at Angola, it funnels water to the river’s west bank, directing it to the Atchafalaya Basin and eventually down to the Morgan City area.

It has only been used twice in its history, in 1973 and 2011, but every year the Corps must notify by mail the roughly 2,500 landowners within the floodway of the possibility. The federal government purchased “flowage easements” from the landowners when the spillway was built, but they continue to own the land.

Cattle can be seen grazing in the shadow of the Morganza structure, where the water flows when it is opened. Before opening it, the Corps must also work with local and state officials to encourage wildlife to relocate, including black bears. Releasing water gradually helps signal to wildlife to clear out.

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In 2019, the trigger for Morganza was almost reached, but it ultimately fell just short. Mississippi officials point to that with bewilderment and disappointment, questioning why so much water must be funneled through Bonnet Carre while the Morganza stays closed.

Are there potential solutions? There may be, but politics and federal government cost-cutting are preventing them from being explored at the moment.

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One key change that was being looked at involved altering the amount of water allowed to be diverted through the Old River Control complex to the Atchafalaya River. The amount of flow through the complex on an annual basis — 30% of the combined flow of the Mississippi and Red Rivers — is locked in place by congressional mandate.

It is unclear whether altering Old River flows would be enough to adequately address the dilemma of the Bonnet Carre. Corps officials say a later “tiered study” could look at how to best operate Bonnet Carre, Morganza and Old River as one system.

Any change will draw controversy.

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