Mississippi River’s Morganza Floodway May Be Opened for Third Time Ever

By | May 23, 2019

A major barrier that keeps the Mississippi River in its current path may be opened for just the third time in its history, potentially flooding a large part of rural Louisiana.

Concern is growing that heavy rains will cause the Mississippi to flood over the top of the Morganza Floodway — a long dam-like structure that is designed to divert 600,000 cubic feet per second of water to take pressure off the river. To prevent that, the Army Corps of Engineers may be forced to open the gates of the barrier.

The river has been high or flooding since last October, engorged by huge rainfalls that have slowed crop planting in the Great Plains and the upper Midwest. The Mississippi between New Orleans and Baton Rouge is lined with energy infrastructure including refineries, and the swell has caused shipping delays in the waterway, a main route for grain, chemicals, coal and oil.

There’s a risk that the river will flood over the Morganza by about June 5, which would render it useless, said Ricky Boyett, a spokesman for the Army Corps of Engineers. To avoid that, its 125 gates will have to start opening by June 2 at the latest, he said.

“The decision to open Morganza Spillway has not been made yet,” said Jean Kelly, a spokeswoman for the Louisiana Department of Environmental Quality. The state’s governor, John Bel Edwards, is scheduled to hold a press conference this afternoon, according to local media.

While the river is flooding, it’s not as severe as in 2011 — the last time Morganza was opened. In February, the Bonnet Carre Spillway was opened to help alleviate flood risks in New Orleans, about 28 miles downstream. After it was finally closed in April, the Army Corps of Engineers opened it again on May 10. The U.S. Coast Guard closed a portion of the Mississippi River near St. Louis because of high water and fast currents on Thursday.

The current round of flooding has lasted much longer than in 2011, said Jeff Graschel, service coordination hydrologist with the Lower Mississippi River Forecast Center in Slidell, Louisiana. Levels on the Mississippi River are a little less than two feet below its record crest that year just upstream from the Morganza barrier.

The Morganza spillway is located about 45 miles (72 kilometers) northwest of Baton Rouge, and if opened, will send water into the rural area between the Atchafalaya and Mississippi Rivers in central Louisiana.

The last time the Morganza was opened, an 80,000 barrel-a-day refinery in Krotz Springs, Louisiana, was forced to shut because of supply disruptions.

Total grain barge traffic was 54% below the three-year average in the week ending May 18, with 369,250 tons moving on the waterway, according to the U.S. Department of Agriculture’s Grain Transportation Report. For 2019, grain shipments are off 26%.

While the Mississippi could dip lower in the next few days, forecasters are expecting a new deluge caused by a week’s worth of thunderstorms across the Great Plains and Midwest to send the river rising again by the end of next week, Graschel said by telephone. A large amount of water is expected to flow into the Mississippi from the Arkansas River, he said.

(With assistance from Kevin Varley and Sheela Tobben.)

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