The Mississippi River: Quo Vadis?

My last post dealt with Louisiana's plan to divert the Mississippi below New Orleans to save coastal wetlands. The picture below shows the river at New Orleans; Algiers Point is on the right and the city proper is on the left, so we're looking downstream.

To provide some perspective on the flow of the Mississippi, its average annual discharge is about 450 million acre-feet (MAF) or 17,700 cubic meters per second (cms). Contrast that to the Columbia (about 200 MAF or 7,900 cms), and the Colorado (14 MAF; 550 cms). Among world rivers, in terms of average annual discharge, it ranks 8th behind the Amazon (4900 MAF; 190,000 cms), Congo (1100; 42,000), Yangtze (890; 35,000), Orinoco (740; 29,000), Brahmaputra (510; 20,000),La Plata (500; 19,500), and Yenesei (460; 17,800). Yeah, it's a big one!

So why is a hydrologist who's done most of his work in the arid western USA blogging about the "Father of Waters"? Why not? My curiosity about the Mississippi River started early in life, but piqued in high school, when I got a copy of a new book, Modern Hydrology, by the late Raphael G. Kazmann, a legendary engineering professor at LSU in Baton Rouge. The book covered far more than just the Mississippi, but I was intrigued by Kazmann's discussion of the river's discharge and flood control.

Later, as a graduate student at the University of Arizona, I heard Kazmann tell a fascinating tale about the river and its "desire" (forgive the anthropomorphism - a trait of water nerds like me) to change its course - "delta switching" - which it had done a number of times over the past many thousands of years.

He described how the river really wanted to flow down the Atchafalaya River, a distributary of the Mississippi, formed by the confluence of the Red River with the Mississippi's main channel at the Louisiana-Mississippi stateline. It's about 170 miles (270 km) long and also serves as a shipping channel.

The Atchafalaya is actually building a delta into the Gulf of Mexico, one of the few places where the Louisiana coast is growing (see below).

If the Mississippi were left to its own devices, it would "prefer" to flow predominantly down the Atchafalaya, a more direct (190 miles or 300 km shorter) route to the Gulf of Mexico, leaving much less water in the main channel. This, of course, would leave the major ports

of Baton Rouge and New Orleans "high and dry", or nearly so. Suffice it to say that's not an option - these are two of the biggest ports in the USA and, along with the associated oil and petrochemical industries, are critical to the USA's economy. So maintaining the status quo is not just important to Louisiana, but to the USA.

The "ideal" (from society's standpoint) flow distribution is to have about 30% of the combined Mississippi River + Red River discharge flow down the Atchafalaya and about 70% down the main channel of the Mississippi. To maintain this distribution, at the behest of Congress the U.S. Army Corps of Engineers constructed an elaborate system, the Old River Control Structure Complex, which was completed in 1963. I have never seen these engineering works in person, but I've heard people, including engineers not impressed by just anything, describe this complex as something amazing.

   

This complex "keeps things right" - maybe not for the natural system, but for humankind's needs. In the above picture of the complex, the Mississippi is to the left, curving to the right in the background. The view is towards the east-southeast.

Kazmann felt strongly (see If the Old River Control Structure Fails? Louisiana Water Resources Research Institute, Bulletin 12, 1980, pages 1-8) that the river would eventually win out, and that most of the flow would wind up in the Atchafalaya's channel. The current mainstem would become an estuary, or perhaps "bayou" might be more appropriate.

John McPhee's book The Control of Nature has an excellent discussion on this issue. Katherine Kemp has a short article on "The Mississippi Levee System and the Old River Control Structure" that's very informative.

"One who knows the Mississippi will promptly aver...that ten thousand River Commissions, with the mines of the world at their back, cannot tame the lawless stream, cannot curb it or confine it, cannot say to it 'Go here or go there' and make it obey, cannot save a shore that it has sentenced." -- Mark Twain, Life on the Mississippi

Comments

[Michael]

Hi, Adam.

You're never too late! I just posted on the Mississippi River. Thanks for the comment and the links - much appreciated!

[Adam Engelhart]

I'm awfully late in the game here, but I just learned of the existence of the Old River Control Structure on Wednesday (due to that day's xkcd comic: http://xkcd.com/748/ ). It's a fascinating piece of engineering.

Anyway, I wanted to write to say that I found a copy of If the Old River Control Structure Fails? online at the LWRRI Digital Water Library ( http://www.lwrri.lsu.edu/dwaterlibrary.html ). The direct link is http://www.lwrri.lsu.edu/downloads/LWRRI_Bulletins/May2005/LWRRI_B12_1980.pdf . Be advised, it's a 300 MB file.

[Michael]

Hi, Jeremy.

Thanks for commenting.

If it is online, it is probably at:

http://www.lwrri.lsu.edu/

You might also try Googling him.

[Jeremy Furchtgott]

Very interesting piece.

Do you know if Kazmann's study is online?

Jeremy

[Michael Brian]

As rivers go, the Mississippi is one of the world’s biggies. It’s 3 734 km (2 320 mi) long and has a watershed of more than 3.2 million sq. km (1,245,000 sq. mi), the third-largest in the world.
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Michael Brian
Mississippi Treatment Centers

[Michael]

Hi, Katherine.

Thanks for commenting.

Yes, your excellent work lives on. I am nowhere near an expert on the Mississippi, but Katrina renewed an interest that was initially whetted by Ray Kazmann's book and lecture so many years ago. It's a fascinating system.

Hope you are staying safe and dry.

[Katherine Kemp]

I'm glad to see that my little article that I wrote as an undergrad is having a lasting impact as a resource. I'm currently living in the Midwest where we are having record flooding, and it's made me think again about the Mississippi's levee system...will this flooding event be the final straw for the Old River Control Structure? After seeing Lake Delton in Wisconsin left high and dry on the news after the river feeding into it carved a new path for itself, I can only imagine what the loss of the Mississippi would do to New Orleans, and the devastation it would cause to the communities along the Atchafalaya. I think this is a topic which needs wider discussion, thanks for keeping it alive!

[Dave Gill]

Thanks, John

I've been fascinated by this subject for a number of years - there was a NOVA about it, then I read McPhee's book. (I still love the "pissing on the volcano" section)