Flooding on the Mississippi River Becoming More Common and Severe

By Becky Gillette

It seems that every year when the Mississippi River rises, it is getting higher and higher. During the past ten years, the frequency of flooding has greatly increased in some areas of the Mississippi Delta. Something isn’t right here.

Peter Nimrod, Chief Engineer of the Mississippi Levee Board in Greenville, isn’t exactly sure why the flooding has become more frequent in the past ten years.

“In 1927, Congress passed the Flood Control Act of 1928, which authorized the Mississippi River & Tributaries Project for flood control measures,” Nimrod says. “The first 80 years we got major high water in only four years, 1927, 1937, 1973 and 1983. We averaged a major flood stage once every twenty years. We have hit that major flood stage four times in the last eleven years, in 2008, 2011, 2016 and 2018. Now we get major flooding every three years instead of every twenty years.”

Improvements have been made to significantly strengthen the flood control system.

“Since the 2011 flood, a lot of repairs were made along the levee system,” Nimrod says. “We have made permanent solutions to all eleven problem areas. Now the problems we are working on are minor and insignificant compared to 2011 when we had all those major problems.”

Nimrod speculates the flooding is being caused by more precipitation throughout the Mississippi River Valley, and more runoff from development in the watershed.

“When you look at some of the historic precipitation, in the late 1800s until the 1927 Flood there was very heavy precipitation and then from 1950 to 1972, there was very little precipitation and we never reached flood stage on the Mississippi River,” Nimrod says. “In my mind I think it has to be a weather pattern of very wet cycles that we are in. Hopefully, we are at the top end of the wet cycle and will stop having so many of these long, heavy rains.”

Kelley Williams of Jackson, who owns a large farm south of Natchez that floods frequently, blames the increased flooding on flood control projects.

“Floods are higher, longer, and more frequent than ever,” says Williams, a former CEO of First Mississippi Corp. “Levees contain the river. The Corps builds them higher and higher.  So, floods get higher too—and more dangerous. The higher and longer the flood, the greater the risk of levee failure. The most damaging levee failure could be between Natchez/Vidalia and Baton Rouge on the west bank.  It could send the Mississippi River to the Gulf at Morgan City.  The course change could be irreversible.”

The mouth of the Mississippi River moves about every 800 years when the old channel gets higher, longer, and flatter from sediments deposited over time.

“It’s about time for a change,” Williams says. “So, how could the Corps buy some time? It could send more flow to the Gulf at Morgan City and lower the river. A lower river would reduce the frequency, duration, and height of floods and risk of levee failure. But Congress said no to more flow 64 years ago.  The Corps still follows that order.  Madness.”

Nimrod understands Williams being sick of flooding.

“Kelley knows if the Corps would push more water out of the Mississippi River into the Atchafalaya River, it would give him some flood reduction in his area,” Nimrod says. “But if they divert more flow to the Atchafalaya, you are going to introduce more flooding through Louisiana and Morgan City. You would also possibly negatively impact navigation in New Orleans. Whatever you do, it is going to have a positive effect one place and a negative effect somewhere else. There is going to be some good and some bad so you have to decide what is the best for everyone.”

If the river changed course, it would have a huge economic impact. It is hard to imagine a New Orleans without the Mississippi River.

Dr. Yi-Jun Xu, a hydrologist at Louisiana State University, said the danger of the Mississippi River taking a new course during a major flooding event has been known for decades.

“The issue has been known for a long time, since the 1940s,” Xu says. “The Old River Control Structure (ORCS) was built in the 1950s to control the flow into the Atchafalaya. Since completion of ORCS, the Mississippi River is diverted to the Atchafalaya River in order to prevent the Atchafalaya from completely capturing the Mississippi River. People have known about this risk for a long time. But what studies have shown is that the risk is higher today because of the river bed. A lot of the sediments have been accumulated so the river bed has increased in elevation. That is a danger for the Mississippi River to change its course into the Atchafalaya.”

What should be done is complicated. Xu said the focus of his work is an assessment of the risk, determining how real the risk is and what flood event would trigger the course change. But as far as solutions, he said that question needs to be directed to the U.S. Army Corps of Engineers.

“They are the people who manage the river and control the hydrology and the ORCS,” he says.

Charles Camillo, executive director of the Mississippi River Commission, said there is no one blanket answer to whether or not flooding has increased on the Mississippi River. Flood frequency and flood severity depend on several factors, especially the baseline being used as the starting point for the comparison. Flood frequency and flood severity also depend on the location along the system.

“For instance, if you asked questions about flood frequency and flood severity in regard to the City of Greenville, you would receive entirely different answers than if you asked the same questions about the river gage at Greenville on the riverside of the levee,” Camillo says. “As a matter of fact, the City of Greenville has not experienced any Mississippi River flooding since 1927. The same can be said of other river towns, such as Cairo, Ill., New Madrid, Mo., Hickman, Ky., Tiptonville, Tenn., Helena, Ark. and Lake Providence, La.”

Camillo says the Mississippi River & Tributaries (MR&T) project is a comprehensive engineering system designed to convey a flood that is up to three million cubic feet per second through the seven states along the lower Mississippi River. The MR&T system uses a variety of engineering techniques to provide enhanced flood protection to the 4.5 million people living in the project’s footprint. Camillo said those techniques include:

An extensive levee system—complete with relief wells and seepage berms—to prevent overflows from flooding developed lands.

Floodways and backwater areas to reduce pressure on the levee system by providing room for the river to expand.

Channel improvements and stabilization features to protect the integrity of structural flood control measures from scour and to ensure proper alignment and depth of the navigation channel.

Tributary basin improvements in the form of drainage ditches, levees, headwater reservoirs, flood gates, and pumping stations that maximize the benefits realized on the Mississippi River main stem by expanding flood protection coverage and improving drainage into adjacent areas within the alluvial valley.

There are also hundreds of non-MR&T project reservoirs in the watershed that provide flood storage and reduce stages downriver.

Camillo says all of these features help to accommodate the natural tendency of the river to flood, while protecting 4.5 million people and 1.2 million residential structures; 22.5 million acres of prime agricultural lands; 108 power plants; more than 500 manufacturing sites, etc.

“Since its inception in 1928, the MR&T project has prevented more than $1 trillion in damages to these key components in the lower Mississippi Valley,” Camillo said. “During the 2011 flood and subsequent floods on the lower Mississippi River in 2016 and 2018, the MR&T system has operated as designed. With each flood event, the system sustained damages that the nation thankfully and wisely helped to repair through supplemental emergency appropriations.”

But the system is only a good as its last performance. Simply put, the Mississippi River is a powerful and dynamic force that requires constant vigilance, he said.

“The nation, the U.S. Army Corps of Engineers, states, local levee districts and the local people can never let their collective guard down when confronting the challenges that living with the river presents, especially in light of the fact that the MR&T project is currently incomplete, built to about 87 percent of completeness,” Camillo says. “Until the MR&T project is finished, although capable of passing significant and record floods, it is incapable of passing its project design flood.”

Camillo says their intention is to continue to maintain and operate the ORCS as designed to ensure the Atchafalaya does not capture the Mississippi.

“Remember, water is the most powerful force in nature,” he says. “We cannot control nature, but we can—and do—harness this energy for the good of this nation.”