Corps Eyes Opening Morganza Spillway

The rain keeps falling in the Midwest, which has seen the wettest year on record. And much of that runoff is bound for the Mississippi River, already in the midst of one of the longest high water periods ever seen.

River gages throughout the Lower Mississippi River are nearing record heights and setting new records for most days above flood stage.

“We are in a historic river flood,” said Col. Michael Clancy, commander of the Corps’ New Orleans District. “It’s the wettest year on record for 124 years, since the National Weather Service began keeping records. We’re breaking records up and down the river right now for longest period in flood stage.”

Clancy was speaking at the 91st meeting of the Inland Waterways Users Board (IWUB), which met in New Orleans May 23.

At Red River Landing, the Mississippi River has been above flood stage (48 feet) since December 27—147 days at press time and counting. The record time above flood stage is 152 days, set in 1927. That record will be broken May 29. The record height at Red River Landing, set in 2011, is 63.39 feet. The National Weather Service forecasts the river will crest at 62 feet there around June 5.

The timing of that forecast crest at Red River Landing matches a notice the U.S. Army Corps of Engineers recently sent to property owners and stakeholders within the footprint of the Morganza Spillway, warning that the agency could begin opening the spillway in less than two weeks.

“Based on the forecast rain in the coming week, we think we’ll hit the trigger for Morganza the first week of June,” Clancy said.

The trigger point for opening Morganza, which diverts water from the Mississippi River through a floodway to the Atchafalaya River, is a flow rate of 1.5 million cubic feet per second (cfs.) at Red River Landing. Forecasts call for the river to approach that trigger point around June 5. The Corps is also afraid the river could overtop the spillway structure around that same time, which would make opening the spillway impossible. Thus, the Corps is considering opening the spillway a couple days ahead of time to prevent overtopping.

Clancy added that opening Morganza is much more complicated and requires much more coordination and communication than the Bonnet Carré Spillway downriver.

“At Bonnet Carré, the Corps of Engineers owns the spillway and we don’t flood anyone,” Clancy explained. “Morganza is a totally different story. We’re going to be deliberately flooding private property. We have to evacuate property and livestock. There are endangered species issues. It’s an incredibly complicated operation.”

The last time Morganza was opened was 2011. Prior to that, the Morganza Spillway was utilized only one other time, in 1973.

Opening Morganza will take pressure off long-stressed levees between Red River Landing and Bonnet Carré, including levees in Baton Rouge, where the river has been above flood stage a record 137 days and counting. The river in Baton Rouge surpassed 35 feet on January 6.

The Corps continues to open bays at Bonnet Carré Spillway, which diverts water from the Mississippi River to Lake Pontchartrain and on to the Gulf of Mexico. The Corps opened Bonnet Carré a second time beginning May 10. As of May 21, the Corps had opened 168 of the spillway’s 350 bays for a total discharge of 161,000 cfs.

“There’s no end in sight for Bonnet Carré,” Clancy told IWUB members.

The trigger point for operating Bonnet Carré is a flow rate of 1.25 million cfs. at the Carrollton Gage in New Orleans, which loosely translates to a stage of 17 feet.

While operating Bonnet Carré protects communities on both sides of the river below the spillway, not everyone supports opening it. Operating the spillway drops the salinity in Lake Pontchartrain, which is typically brackish, and injects fresh water into Lake Borgne farther east and into the Mississippi Sound, prime fishing grounds for oystermen, crabbers and shrimpers. What’s more, some have attributed an uptick in dolphin and sea turtle deaths earlier this spring to the first opening of the Bonnet Carré Spillway.

Mississippi Attorney General Jim Hood issued a letter to Maj. Gen. Richard Kaiser, commander of the Corps’ Mississippi Valley Division and president of the Mississippi River Commission, May 21 bemoaning the Corps’ flood management strategy.

“I write to you because I have profound concerns regarding the need to both protect our citizens and their properties from river flooding and reduce adverse impacts to the marine ecosystem from floodwater management,” Hood said in the letter. “I am particularly concerned about the opening of the Bonnet Carré Spillway.”

Hood mentioned the deaths of dolphins and sea turtles, along with the impact on Mississippi’s fishing and tourism industries. Hood also pointed to backwater flooding from the Yazoo River, which has inundated an estimated 512,000 acres in the state’s Delta Region, including 208,000 acres of farmland.

“Farmers are unable to plant crops under water, and residents have evacuated or remain trapped,” Hood said.

Hood asked for a meeting with Kaiser “to better understand the situation and the Corps’ plans to protect Mississippians and our state’s natural resources in both the Coastal and Delta regions.” He also asked to see the Corps’ environmental monitoring plan and environmental impacts study with regard to Bonnet Carré, the Corps’ plans to reconfigure its flood control plan to avoid the frequent use of the Bonnet Carré, and the agency’s plan “to address federal regulations to provide greater flexibility with flood control management in the Mississippi River Valley.”

The letter is just the latest dust-up between the state of Mississippi and the Corps. Earlier this year, Mississippi Secretary of State Delbert Hosemann and Hood announced the state was suing the federal government over the “unconstitutional taking” of thousands of acres of state-owned land due to persistent river flooding.