Corps predicts Morganza spillway opening not needed to control flood conditions along the Mississippi River

The U.S. Army Corps of Engineers reported Monday that it won’t need to use the Morganza Control Structure because the flow of water in the Mississippi River isn’t expected to be strong enough to trigger the opening.

The flow of water is one of the river conditions that need to be in place in order for the structure to be opened. The river is expected to meet one condition, of 57 feet at the structure, but it’s not expected to reach a flow of 1.5 million cubic feet per second. The Mississippi River flow is expected to top out at 1.44 million cubic feet per second.

Even without the Morganza opening, water levels within the Atchafalaya River basin are expected to rise because 30 percent of the Mississippi River water is diverted to the Atchafalaya River.

Water levels in the Atchafalaya River are expected to get up to 20 feet on Sunday in Butte La Rose and up to 8 feet on Jan. 21 in Morgan City. At 20 feet in Butte La Rose, some minor flooding is expected. At 8 feet in Morgan City, areas on the river side of the floodwall in Morgan City and Berwick will flood, according to the National Weather Service.

Marc Folse, Morgan City chief administrative officer, said businesses on the river side of the floodwall have already taken the necessary precautions.

“Eight feet is manageable and we’ll take it. It’s not terribly out of the norm,” he said.

Early forecasts indicated that the water could get as high as 9.5 feet at Morgan City, which would have caused more problems, but the lack of strong rains and a steady north wind have helped lower river level, Folse said.

Even with lower water levels forecast, there are still concerns about flooding because a south wind or high tides could push more water into the river and high water last year could have left some channels with less water-carrying capacity, he said.

“Eight feet is still a big flood,” said Tim Matte, executive director of the St. Mary Levee District.

The St. Mary Levee District is working to close off Bayou Chene which has been a conduit for backwater flooding.

Used in 2011, the levee district is installing a combination of sheet piling, rocks and a barge to keep water from backing up from the Atchafalaya River and putting more water in communities in the Lake Verret Basin, St. Mary, western Terrebonne and other low-lying areas. A plan to build a permanent structure in this area is going through the permit process, Matte said.

Closer to New Orleans, the Corps continued to open bays at the Bonnet Carre Spillway. Twenty of the bays were opened Sunday and another 18 were opened Monday. Based on Monday’s forecast, it’s expected that fewer than 200 of the 350 bays that make up the structure will need to be opened. A week ago, forecasts indicated that all 350 would need to be opened.

One of the reasons for the forecast changes is a reduction in water flow from the Arkansas River into the Mississippi River. That reduction also helps out the Atchafalaya River forecasts, said Jeff Graschel, service coordination hydrologist with the Lower Mississippi River Forecast Center.

It could take a couple of months for water levels to return to normal for this time of year, he said.

Follow Amy Wold on Twitter, @awold10.

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