A mightier Mississippi River causes navigation hazards

The Army Corps of Engineers is reviewing how it operates its giant flood control tools
Updated: May. 1, 2019 at 9:45 PM CDT
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NEW ORLEANS (WVUE) - The steam-powered calliope signals another cruise of the Steamboat Natchez in New Orleans as a boatload of tourists escape, for a couple of hours anyway, to a different place and time.

However, this is not Mark Twain’s Mississippi River.

Natchez Captain Don Haughton boasts 36 years of experience on the river and is noticing a change.

“I’ve never seen it this high for this long," Haughton said.

Haughton and others who command or pilot vessels through New Orleans must deal with one of the most treacherous turns on the entire river, the crescent-shape at Algiers Point.

“[It] makes a hard turn right here," Haughton said, "And all that water can’t make that turn. So, it backs up and runs upstream at our dock.”

Haughton said the Natchez handles the turn well, but vessels of every size can have a difficult time in the bend as the current catches them.

At its current flow, the Mississippi would fill the 125 million-cubic-foot interior space of the Superdome in a little over a minute and a half.

David Ramirez, Chief of River Engineering and Water Management at the Corps New Orleans District said heavy rainfalls have contributed to the river’s high waters.

“We’re seeing rainfall amounts that exceeded over 100 years in the Mississippi Valley,” Ramirez said.

The Mississippi drains roughly 41 percent of the United States, making it third only to the Amazon and the Nile among the world’s largest drainage basins.

However, it is arguably the most elaborate and heavily engineered drainage system on the planet.

Upriver from New Orleans, the Bonnet Carre Spillway acts as a giant relief valve, diverting river water into Lake Pontchartrain and sparing New Orleans from flooding.

North of Baton Rouge, the Morganza Spillway provides another layer of defense.

As it has through the centuries, the Mississippi wants to shift course, bypassing New Orleans and Baton Rouge and darting down the Atchafalaya River toward Morgan City.

The Old River Control Structure -- actually a series of structures -- prevents that by sending just enough water down the Atchafalaya (30 percent of the combined flow of the Red and Mississippi Rivers) to placate the Mississippi.

While there have been periods of unusually high water in the past -- notably the 1970s -- some experts like civil engineer H.J. Bosworth, believe the current high Mississippi represents a new normal.

“Every year, we should expect the potential for more and more water as our climate changes and as the landscape changes,” Bosworth said.

Bosworth pointed out man has altered more than simply the river banks, adding big box stores, subdivisions and other developments throughout the basin.

Water once absorbed into the ground, now runs off directly into rivers and streams as it begins it long trek down the Missouri, Ohio, Arkansas, Tennessee and other tributaries of the giant river.

“If somebody in the Dakotas or somebody in Iowa or Minnesota wants to build a subdivision, the local authorities there think, ‘Great go ahead and do it,’” Bosworth said.

Despite frequent calls on social media or in newspaper forums to run the spillways more often, federal law actually limits the Corps’ options.

The Bonnet Carre, for example, can only be operated when the river’s flow in New Orleans reaches 1.25 million cubic feet of water per second.

Nevertheless, Republican Congressman Garret Graves argued there are systemic problems with how the Corps manages the river, and the various tools in the flood control toolbox.

Corps hydrologists and LSU scientists have identified a large slug of mud and sand on the river bottom, stretching from Vicksburg to Baton Rouge and steadily creeping downriver, which has the effect of raising the river bottom.

“That is a dangerous situation because it is decreasing the capacity of the Mississippi River system," Graves said. "It is making us down here at the bottom of this huge watershed more vulnerable.”

Graves, a frequent Corps critic, authored language calling on the Corps to evaluate changes in the river and possible responses.

“We’re looking to see what can we do in the future that might be better than what we’re doing right now," said Jeff Varisco, a project manager.

Any significant changes to the operation of spillways or Old River would require congressional approval.

While the Corps said its assessment will take three years, Graves is not satisfied.

“We don’t have three years," Graves said. "The urgency is greater than that.”

Toying with the spillway’s operations opens up a host of other issues, some of them not directly related to flood protection, according to Mark Davis, director of the Tulane University Institute on Water Resources Law and Policy.

“Anytime you open the levees for any reason at all, you change the river,” Davis said.

More common use of the Bonnet Carre Spillway could bring more harm to Lake Pontchartrain and potentially run afoul of environment laws, such as the Marine Mammal Protection Act.

The Morganza Spillway involves other issues since people live in and operate businesses in the floodway.

“If you start putting more water down Morganza, and there are certain reasons you might want to, certain reasons I might want to, that will also have effects on the people who live and work in the spillway, who own property there," Davis said.

Changing how the Mississippi flows could build up sediment in other spots along the river bottom.

“It doesn’t mean you can’t do it," Davis said. "It just means you have to think it through first.”

Bosworth said he sees a need for some kind of national water policy or database to understand how water moves through the system.

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