The Atchafayala, A Twentieth Century Phenomenon

Atchafalaya, a Choctaw word meaning “long river,” is a distributary of the Mississippi River. Leaving the Mississippi near Simmesport, it runs approximately 125 miles to empty into the Gulf near Morgan City. Its thirty-five-mile-wide floodplain is America’s largest swamp wilderness.

Because of the incredible changes that have taken place on the river, some geologists refer to the Atchafalaya as the “phenomenon of the twentieth century.”

Looking at the broad, turbulent river today, it is hard to imagine that once upon a time a person could almost jump across it. In a 1973 newspaper article, one man remembered, “[G]randma . . . said that back before the Civil War when she was a child growing up on the river, it was a docile little stream. Her story, passed down through the family, said the Atchafalaya was so small in places in those days that you could throw a log across it and walk over.”

The river’s transformation into a mighty waterway is a cautionary tale of man’s sometimes reckless interference with Mother Nature. 

The Atchafalaya begins where the Mississippi, Red and Atchafalaya come together. In the early 19^th century, the Red flowed into the Mississippi, but the Atchafalaya flowed out of it. A huge log jam, or “raft,” at the head of the Atchafalaya acted as a dam and restricted the amount of water that could enter it.

When a severe drought in 1839 dramatically lowered the Atchafalaya, people claimed that it could be crossed on a fifteen-foot plank.

Government officials finally agreed to improve navigation on the Atchafalaya and hired Captain Henry Miller Shreve to clear the log jam. This project, however, set in motion a chain of events that completely transformed the river. 

[Read about all the different ways you can explore the Atchafalaya Basin: Here are our guides to Biking, Camping, and Paddling one of Louisiana's most majestic natural resources.] 

For three hundred years, the log jam had forced the Red River to flow into the Mississippi. When Shreve cleared the raft, it was as though a plug had been pulled and the Red suddenly began discharging its water down the Atchafalaya. When the Mississippi overflowed during floods, even more water poured into the basin. In a short time, this huge increase in water volume scoured out what had been a minor stream channel and turned it into a significant river.

Faced with an ever-widening river, landowners began building levees to try to contain the Atchafalaya, but the banks caved in after every flood, and they had to keep moving levees, homes, and buildings farther back. One cotton farmer living below Simmesport was forced to move his house and store twice.

The millions of tons of sediment that were deposited in the basin every year also transformed the landscape. Whenever the river flooded, these sediments filled in much of the backswamp and created new land that was soon covered in hardwood forests.

In the lower basin, the sediments at first created deltas in the large lakes and then gradually filled them in. During the Civil War, Yankee gunboats patrolled Grand Lake and Six Mile Lake. One hundred years later, Grand Lake had essentially disappeared and Six Mile Lake was rapidly filling in.

The steady growth of the Atchafalaya River can be seen in the increasing amount of Red River water roaring through it year by year. In 1850, it was less than ten percent, in 1920 it was eighteen percent, and by 1950 nearly one-third of the Red River flowed down the Atchafalaya.

The new and bigger Atchafalaya dramatically changed the basin’s ecosystem, but that was not the most significant result of Shreve’s “improvements.” Water seeks the path of least resistance and about every thousand years the Mississippi River changes course to find an easier route to the Gulf. The lower Mississippi has been in its present channel for about a thousand years, so it’s time for a shift. 

The Atchafalaya channel is 190 miles shorter to the Gulf than that of the Mississippi, and it has a steeper grade. As a result, the Mississippi began trying to change course and flow down the Atchafalaya soon after Shreve removed the log jam.

To keep that from happening, in 1963 the federal government completed a massive concrete barrier that regulates the amount of Mississippi River water that can discharge down the Atchafalaya. It is called the Old River Control Structure.

The structure nearly collapsed during the devastating flood of 1973, and today a close eye is kept on it during abnormally high water. If the Old River Control Structure should ever fail, much of the Mississippi would divert down the Atchafalaya, and there would not be enough water in the lower Mississippi to accommodate ocean-going vessels. Salt water would intrude upstream as far as Baton Rouge, and Louisiana’s economy and geography would be changed forever.

Dr. Terry L. Jones is a professor emeritus of history at the University of Louisiana at Monroe. For an autographed copy of “Louisiana Pastimes,” a collection of the author’s stories, send $25 to Terry L. Jones, P.O Box 1581, West Monroe, LA 71294.