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All Eyes on Mississippi River Levees, Spillways as Flood Tensions Continue

May 11, 2011 at 12:00 AM EDT
Crews filled sandbags and shored up levees along the Mississippi River as enormous volumes of water surged south. Jeffrey Brown takes a closer look at the levee and floodgate system with the Association of State Floodplain Managers' Larry Larson and Author John Barry.
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JEFFREY BROWN: Flood tensions on the Mississippi River kept building today. The drama played across a vast stage, south from Memphis to the Gulf of Mexico, as Army engineers tried to lighten the load at key pressure points.

The enormous volume of water surging down the Mississippi is now moving at more than double the river’s normal speed. And there’s mounting urgency to finish sandbagging before it’s too late. Boats navigated the city streets of Tunica, Miss., today. The casino town had already lost an estimated $87 million in gaming revenue, but townspeople said they would get by.

MELANIE DELHOME, Tunica, Miss.: We love it here. We don’t want to leave here. We want to go home. And we’re going to do whatever it takes to stay there.

JEFFREY BROWN: The moving disaster is testing a $13 billion flood control system that protects the land and the four million people who live in the potential flood zone along the Mississippi. It was begun after 1927, when record flooding on the great river killed hundreds of people.

All told, an elaborate system of levees stretches 2,023 miles, starting in Illinois and Missouri, and ending in Louisiana, near where the Mississippi dumps into the Gulf of Mexico.

Along the way are a series of floodways and spillways, channels that can carry surplus water away from a levee when needed. It was near the New Madrid Floodway in Missouri that the Army Corps of Engineers blew up a two-mile stretch of levees last week to spare the town of Cairo, Ill. As a result, 130,000 acres of nearby farmland in Missouri were flooded.

Farther downriver, near Baton Rouge, the Corps has asked permission to open gates on the Morganza Floodway for the first time since 1973. That would flood thousands of acres, but might prevent even worse flooding in seven parishes. The Corps already opened some of the gates at the Bonnet Carre Spillway 30 miles north of New Orleans to ease pressure on that city’s levees. Now some of the levees themselves need reinforcing against the increasing water pressure.

KAVANAUGH BREAZEALE, U.S. Army Corps of Engineers: We are actually on the backwater levees. These levees attach to the mainline Mississippi River levees. And what we are doing is, just for a precautionary measure, we are adding a polyurethane-type plastic to the backside of the levee.

If they, water get — if the water gets high enough that it flows over the levee and flows down the backside, this helps with erosion to keep it from damaging the levee if the water should go over.

JEFFREY BROWN: The potential for catastrophe was evident at Memphis, Tenn., where the water may take weeks to retreat, after cresting on Tuesday. These before-and-after photographs taken from space show the effects on the city and its surroundings. Damage estimates so far have reached $320 million.

Across the river, in Arkansas, the damage to farms and crops is already much higher, at $500 million and counting.

NATHAN REED, Arkansas: I have got a neighbor that’s got $2.5 million worth of wheat flooded right now. And it’s — I mean, it’s gone.

JEFFREY BROWN: Now, town after town along the southern Mississippi can only wait. Over the next week, the river is projected to crest at or above records set during the Great Flood of 1927.

And we take a closer look now at the levee and floodgate system.

For that, we turn to Larry Larson, executive director of the Association of State Floodplain Managers, representing flood specialists in both the public and private sectors, and John Barry, a New Orleans resident and author of “Rising Tide: The Great Mississippi Flood of 1927 and How It Changed America.” He joins us tonight from Memphis.

Larry Larson, starting with you, is it, in fact, correct in terms of its construction and mission to think of this all as one system?

LARRY LARSON, Association of State Floodplain Managers: Well, in fact, the Lower Mississippi River from Cairo south was designed as a system, correct.

It has a series of levees, thousands of miles of levees. And then — and then along the points when the water gets really high and constrained by those levees, it provides relief points through spillways and floodway bypasses. So, it is — it’s intended and does operate as a system, correct.

JEFFREY BROWN: And just to fill in that — the details a little bit more, so, you — the floodgates and the spillways are when the water — they’re stuck there, right? And when the water gets a certain height, that’s when they come into play?

LARRY LARSON: Yes. Typically, they wouldn’t be open, because, if you have a small amount of water in the river, you want to keep that water there, because, remember, the water is all — the river’s also used for navigation. So, you want to keep the water there. But when the water gets extremely high, it threatens to overtop the levees.

So, when it gets extremely high, you need to provide relief points to allow some of the water to escape the main channel and flow in other directions.

JEFFREY BROWN: Now, John Barry, we talk a lot about the 1927 flood. What was the flood protection system like before that and what were the major changes afterwards?

JOHN BARRY, “Rising Tide: The Great Mississippi Flood of 1927 and How It Changed America”: First, let me also add that I’m on the board that oversees several levee districts in metro New Orleans. So, I have not simply an academic interest in this.

Prior to the’ 27 flood, the Corps of Engineers had what they called the levees-only system. And that’s pretty self-explanatory. The river is capable of filling its entire floodplain of 35,000 square miles and it came close to doing that in 1927.

At its widest the river stretched probably over a hundred miles wide. So, it was a true inland sea. And there’s enough water in the river right now to do that. But, as Larry was saying, there is a sophisticated system and part of that system involves these floodways that essentially give the river room to operate.

They — really takes up part of the floodplain. There is going to be flooding in this here, not only a relatively little bit in Memphis, although, if I had suffered a flood, it wouldn’t seem so little to me, but considerably more along the Yazoo River. Pretty soon, it will start getting quite serious, I think.

And I think it’s inevitable the Corps of Engineers opens the Morganza Floodway north of Baton Rouge, which runs for 100 miles more than that, 20 miles across. And, frankly, that’s going to threaten some people, probably several thousand people in Louisiana. That’s a lot of land.

JEFFREY BROWN: And, Mr. Barry — yes — is what we’re dealing with today all from the aftermath of 1927, or have there been constant fixes, updates and so on? In other words, is this system — has this system mostly been in place all this time?

JOHN BARRY: Well, it’s been in place pretty much from the ’50s.

The — the — although the spillway immediately above New Orleans, which they opened early this week, that was first used in ’37. They had just finished construction of it. They have made changes. The biggest one would be in 1973. This is probably the second biggest flood in history — 1927 was the biggest; ’73 was probably third.

And, in ’73, when they did — the only other time they opened the Morganza Floodway, the river was powerful enough that it almost destroyed the control structure that it was pouring through. And they obviously recognized that weakness and buttressed it, built another control structure and strengthened that considerably. That is the main change from the design that came out of the ’50s.

JEFFREY BROWN: Now, Larry Larson, we also keep hearing about decisions and tradeoffs that have to be made about opening the floodgates and flooding some farmland in order to save other areas.

Has that always been with us as well? I mean is that designed into the system that these kinds of decisions and tradeoffs are going to be made?

LARRY LARSON: That was designed into the system after the 1927 floods. And it’s not a unique approach. It’s been used elsewhere in this nation. We use it in different rivers. It’s on the Sacramento River and other areas.

It’s used in other nations. China has major bypass systems and storage systems where, when the major industrialized cities are threatened, they flood farmland and other land. It’s a tradeoff. And in this case, the — at the Birds Point-New Madrid Floodway that was opened up by the Corps, that — the Corps was directed to buy flooding easements for that land in the late ’20s, so that, when the river did get this high, then there were — part of the plan is to open that levee across the river and relieve the pressure on the levees at Cairo, Ill.

JEFFREY BROWN: And is there — how much leeway is there for officials? Or how much of this is built in — built in into guidelines, or is it always a question of making a new — a decision each time?

LARRY LARSON: Well, pretty much…

JOHN BARRY: Well, there’s…

LARRY LARSON: … the Corps has to — has to make that decision. It’s in the plan. It’s in the operational plan. When the river gets to a certain stage, they know it threatens the levees on one side of the river, and, therefore, they’re directed to open it on the other side, the same thing true, as John talked about, as we get down by New Orleans on the other bypasses, Morganza and so on.

At a certain stage, the plan is set up to say, when the river reaches this stage, provide those relief valves.

JEFFREY BROWN: And, Mr. Barry, of course we — we — there is criticism. There’s always — probably always criticism of these decisions. Does that — does that go back to 1927 and the aftermath as well, in terms of the tradeoffs?

JOHN BARRY: Well, the Corps took a lot of heat, deservedly so, in 1927. I think some of that disaster you could lay at the Corps’ doorsteps, just like Katrina.

However, in terms of — since ’27, on the Lower Mississippi River, I think the Corps has performed pretty well. And I think they have made — I think it was a close decision on the Birds Point Floodway, because the town of Cairo, the value of that is not exactly enormous vs. the farm property.

But as you get to the Baton Rouge and New Orleans metropolitan area, vs. agricultural land that you have — already own a flood easement for, so the people in the floodway know it can be used for that, and the alternative is to threaten both Baton Rouge and New Orleans, that is a pretty easy decision to make.

I mean, this flood would overtop the levees in those cities. And overtopping means potentially a disastrous breach that could flow for weeks that would, in fact, probably rival or be worse than Katrina.

JEFFREY BROWN: Well, what — well, what do you worry — just, in our last minute, Mr. Barry, what — you mentioned Katrina. I mean, what do you worry about now? When you look at this system, what point — what points do you look at and still worry about?

JOHN BARRY: Well, I mean, the system has performed very well many times. So, you know, you always have to monitor levees. You — there’s always going to be some problem on some levee, sand boils and other problems developing, but you address them. That’s why you have constant surveillance and constant vigilance.

This flood is within the design capacity of the system. I won’t say that I’m not worried. I’m very alert, but — I mean, it’s a serious flood, but there’s no particular weak spot. You know, having said that, there are going to be thousands of people who are flooded, some already in Memphis, more in the Mississippi Delta, and when Morganza opens.

You know, the Corps does have a trigger. When the river exceeds 1.5 million cubic feet a second, they’re going to open Morganza. And it will exceed that, and I’m certain they will open Morganza.

JEFFREY BROWN: All right. Well, thanks for the explanation and the history.

John Barry and Larry Larson, thanks for joining us.

LARRY LARSON: You’re welcome.

JOHN BARRY: You’re welcome. Thank you.