US vs. Nature: What It Takes to Stop the Mississippi River from Changing Its Course | environment

Baton Rouge and New Orleans exist because of the Mississippi River, and vast swaths of the region and nation’s economy have always depended on it. But the great river does not always flow where it does now.

And if it weren’t for a 60-year-old collection of dams, gates, waterways, and canals called the Old River Control Structure, the Mississippi likely moved away from those cities already.

Located in the back of the Louisiana Boot, where the Mississippi, Red and Atchafalaya rivers meet, the structure may have prevented the Mississippi River from switching course and sending the majority of its flow down the Atchafalaya River in the late 1970s or early 1980s, the Corps of Engineers officials who run it say.

The battle of the ancient river control structure to keep the Mississippi, Atchafalaya, and Red Rivers in their places, circa 1950, has attracted the interest of writers and researchers who see it as a powerful symbol of humanity’s struggle to bend nature to its will.

“Nature, in this place, has become an enemy of the state,” concludes author John McVeigh in his 1989 book Nature Control, which examined the ancient river complex and other attempts by people to tame nature.

Some researchers who study the Mississippi say the Legion can’t stop nature, and the Mississippi River will move someday. But Corps officials are confident that they and Old River are still up to the task and that a change of course for the Mississippi is highly unlikely any time soon.

However, after decades of fighting in nature, Old River is under more pressure than it has ever been before, Corps officials say.

“We’ve seen flooding at the highest frequency we’ve ever seen, so these structures are under great load, you know, more often than ever,” said David Ramirez, head of the Corps’ River Engineering Branch in the Arab Republic of Egypt. New Orleans area. “And they are not young.”

In the face of these facts, the Corps plans a major inspection that will include temporarily cutting an important structure, known as a low sill structure, from the Mississippi River. Engineers will make sure the structure is still strong enough to keep Mississippi where Louisiana needs it.

He added: “They were operated in the 1960s, so just looking to the future, if we’re going to continue to have floods of this frequency and this magnitude, it was just decided that maybe it’s just wise, let’s just take the water out of it and get to it and just make sure we feel confident that we have A structure in place that can do what it’s supposed to do.”

flood stress

The last time the Legion worked like this, it was after a low threshold structure approached failure.

The 1973 flood caused one of the Low Sill Guide walls to collapse and swept under a wide area of ​​its foundations, all the way to the steel support piers. The Morganza Spillway had to be opened down the river to relieve the pressure. In 1987, the Corps blocked the Mississippi River to make major repairs to the lower sill.

Even after repairs, Low Silll couldn’t handle the stress caused by the flood waters as well as it once did. Therefore, before those repairs began, the Corps built the additional structure to compensate.

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The accident shows the stress that great floods can put on the ancient river. Since then, the complex appears to have handled major floods in 2011 and 2019 without major damage.

But as climate change causes more extreme weather events, the Corps is planning for more major floods in the future.

To study the lower sill more closely, the Corps plans to build a large dam, likely an earthen, to block river water from the 566-foot-long structure, which usually remains covered by water, allowing the Mississippi River to flow over it into the Red. Wachavlaya.

Ramirez said Corps officials are still working on the details of the dam and the planned inspection, as well as any potential repairs and floodwater treatment in action.

Underwater inspections are carried out regularly, but Corps officials believe that removing all water around the lower threshold will provide a much better appearance and provide the ability to make necessary repairs.

Ramirez noted that the work will take place during the traditional low-water period in Mississippi, which begins in August, and may not last more than 90 days.

“We don’t want it drying up in the winter because that’s when the rains start and the water starts to rise,” he said.

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curb nature

For thousands of years, the river has been rolling across southern Louisiana like a garden hose at full blast. It changed course every thousand years or so to find steeper and more direct roads into the Gulf of Mexico where the old roads became elevated and clogged with silt.

These cyclical natural forces received some help from the humans in Old River.

The removal of major crises in the Red and Atchafalaya rivers helped separate those waterways in the 19th century. Besides the early drilling of the Mississippi short cut in the Old River, the Atchafalaya, which eventually joined with the Red, was allowed to deepen, expand, and begin to capture more and more of the Mississippi’s flow through the connection in the Old River.

By the early 1950s, researchers realized that the Mississippi River would begin to flow into the Atchafalaya, leaving it to its own devices. This means that eventually, the river will stop flowing past Baton Rouge and New Orleans in any significant way.

This fear is what prompted the construction of the ancient river complex.

The structures were designed to lock the waters of the time: the combined flows of the Red and Mississippi over the Old River were split 70/30 between the Mississippi and Atchafalaya down the Old River.

The split keeps the entire state of Mississippi able to support international river trade, providing fresh water to more than 1.2 million people in the New Orleans area, and the many industrial facilities that support the state’s economy.

How long will it last?

But Yi-Jun Xu, a professor of hydrology at LSU, believes that a major flood or other dramatic event, will one day break the Mississippi — likely permanently.

Shaw and other researchers made exciting findings in late 2017 that the bottom of the lower Mississippi River, which began a few miles under the ancient river, has risen 30 feet since 1992. Since then, he and others have shown that the Atchafalaya River below the ancient river deepens at the same time.

Combine that with slowing river speeds and the possibility that climate change will dump more water into the river, and you have the seeds for the next great change in the Mississippi, Shaw argues.

“We believe the system will fail at some point,” he said.

He added that the exact time is unknown. But if the river turns completely, the flows will be significantly reduced and the river can turn from Creeping Bay to Baton Rouge.

Torbjörn Törnqvist, a professor of geology at Tulane University, noted that hurricane risk remains a greater immediate concern for the state. But he said rising sea levels could increase the possibility of a major shift in the river’s course, what is known in scientific circles as a “reversal.”

“There is some evidence from the geological record that eruptions become more frequent when rates of sea level rise increase,” he said. They also tend to move farther inland due to sea level rise.

Corps management plans for the river date back to the period after the Great Flood of 1927. Corps officials have heard concerns about climate change and a desire to take another look at the 70/30 split in the ancient river, Ramirez said, in part to restore coastlines.

The agency was approved last year and is trying to drum up funding for a comprehensive look at the administration of Lower Mississippi.

“So this is a big study that we have to look at and see: is the system still relevant,” Ramirez said. “Do we need another structure? Should we act differently? What changes need to be made?”

Craig Colten, a professor emeritus of geology at LSU who has spent his career studying Louisiana’s infrastructure and battling with nature, drove over the lower stratum during a ’73 flood when he was a curious student at LSU. He remembers the horrific feeling of the structure shaking from the flowing water.

He welcomes the Corps’ new view of things but believes the agency is already behind attempts by other parts of the military to account for climate change. Colten noted that infrastructure changes are moving slowly.

While the agency may have confidence from its past experiences in Old River, the future may bring new challenges.

“We still haven’t seen a flood really go through, really, significantly ’27 or ’73. I don’t know it’s been fully tested, and I think with the amount of rain we can get in the spring these days, it will be tested,” Colton said.

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