Great Flood Of 1993

The Mississippi, No Longer Muddy, Still a Threat: Steven Solomon

June 10 (Bloomberg) -- Reporter Peter Heller narrates a slideshow of photographs that chronicle flooding and flood-control efforts along the Mississippi and Atchafalaya rivers in Louisiana. In May, Mississippi water levels rose to unprecedented heights. The Army Corps of Engineers released water from the lower part of the river through a series of flood gates called the Morganza Control Structure to prevent the inundation of New Orleans and Baton Rouge. The torrent raised water levels in Louisiana's Atchafalaya River basin by more than 20 feet. (Photos by Franco Pagetti for Bloomberg Businessweek and by Getty Images. Source: Bloomberg)

As the floodwaters slowly recede along the lower Mississippi River, we can begin to take stock of the flood of 2011, the most devastating since the epic deluge of 1927.

Most striking, by far, is what didn’t happen: Although many people and communities suffered, overall economic and social life in and around the most important arterial waterway in the U.S. suffered only minimal injury. The national economy dodged a bullet at a vulnerable moment.

What went right? First and foremost, the emergency flood strategy devised by the Army Corps of Engineers after the 1927 disaster proved out. Think of it like this: The Mississippi Valley just south of St. Louis to the Gulf of Mexico is essentially a 600-mile funnel that drains two- fifths of the continental U.S. from the Rockies to the Appalachians and serves as the commercial lifeline for the heartland’s 12,000-mile inland waterway transportation network.

Until 1927, the Corps tried to forcibly contain floodtides within a narrow corridor of high, strong levees. But in 1927 the mighty Mississippi burst its levees, inundating an area nearly the size of New England ; displacing 600,000 people; drowning farmland; disrupting barge transport of grains, fuel and industrial goods; and tearing the economic and social fabric of the nation.

In response, the Corps built safety valves to divert excess water through floodways -- essentially temporary rivers parallel to the Mississippi -- to protect big cities and industries downstream. It took seven decades, but the flood of 2011 was the big test, and the plan passed with flying colors.

Still, having dodged disaster this time does not protect us from new crises brewing on the river. The Mississippi itself is changing, thanks to altered precipitation patterns in the Midwest, ongoing natural and man-made changes within the river, development on its floodplains and other factors.

Perspective

Let’s see if we can relate the Missouri River to something in your refrigerator.

We are embarking on a dangerous course because we’re going to use mathematics. Anyone who was a “C” student in math recognizes the perils of doing so. But we plunge ahead, not trusting our own figuring.

The runoff from heavy snowfall far upstream and heavy rains over the northern part of the Missouri River basin have upstream reservoirs full–and then some. Those reservoirs are designed to contain that water so it can be released in an orderly manner into the Missouri River each spring to (1) maintain water levels for various purposes and (2) restrain water levels to limit flooding downstream.

That does not mean those reservoirs are designed to prevent floods. They’re designed to manage them. Mother nature cannot be controlled. At best she can be managed but every now and then event he best of us rebels against being managed. And Mother Nature is no different. This is one of those times.

The Corps of Engineers, which manages that series of upstream reservoirs, is bleeding off water from them. It’s like an experiment we did in science class in grade school where we filled up one glass of water until it overflowed into another glass of water until it filled up and overflowed into another one, and so on. The hope is that you’ll run out of water before the last glass overflows. This year all of the glasses are overflowing.

The reservoir closest to us is at Gavins Point on the Nebraska-South Dakota border. It is releasing water at 150,000 cubic feet per second. The Corps of Engineers talks in kcfs (“k” meaning “thousand). How much is that to you and me?

Next time you empty a gallon container of milk, fill it with water. Do it with the next gallon container. And the next. And the next until you have seven. Then fill the eighth container about halfway. That’s the equivalent of one cubic foot of water–7.48 gallons. One cubic foot. And Gavins Point is releasing 150,000 of those EVERY SECOND.

If you had 1,122,000 of those milk containers, you would have as much water as is coming out of the Gavins Point Dam every second. If you had 67,320,000 of those containers, you would have as many gallons of water as are pouring through the flood gates every minute. And it’s all going into the Missouri River channel.

But the Missouri River can hold a lot of water. At 6:30 this Tuesday morning, the Corps measured the amount of water flowing past its gauge at St. Joseph as being 165,000 cfs. That’s water from Gavins Point as well as runoff from recent rains in Nebraska, Iowa, and northwest Missouri. On the worst day of the great flood of 1993, the Missouri River was flowing past and into St. Joseph at 335,000 cfs. In the great flood of 1951, it was 397,000 cfs.

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