things kevin hates

This year’s Mississippi River flood is the worst in decades, with record flood stages set in many places throughout the system. There are two main ways to deal with the threat of river flooding:

1) Build huge levees to contain the water.

2) Create outlets where water can be released from the river.

There are a few other possible solutions, but those are the two major ones. Unfortunately, each has its drawbacks. Levees force a river through a narrower path; the only place for the water to go is up, causing the river to get higher, so that the levees must be built taller, and so on. Along the Mississippi, the building of levees has historically been combined with a practice of shutting off almost all of the natural distributaries of the river. It doesn’t take an expert hydrologist to figure out that closing off places where water flows out means more water downriver.

Using outlets of some sort—diversions into other rivers, spillways, or simply flooding large areas of low-lying land—can damage the property or livelihood of whoever owns the land that is deliberately flooded. In some cases—for example, the Bonnet Carré Spillway—only a small amount of land is used. The Bonnet Carré is roughly six miles long and two miles wide; it empties into Lake Pontchartrain. Though the spillway is used for recreation purposes when not in use for flood control, there are no land owners to appease. Thus, it is fairly low-risk (from a political standpoint) to open it up. Sending dirty river water into the lake does annoy the environmentalists and the fishermen, but all things considered it’s not going to piss anyone off too much.

However, the two other major outlets along the Mississippi present a much greater risk to property when opened. One of them is the Bird’s Point-New Madrid Floodway in Missouri. A so-called “fuse-plug” levee is designed so that it can be blown up, allowing the river to flood more than 200 square miles of farmland. As you could probably guess, the farmers don’t really want to see that floodway opened. In fact, they took the Army Corps of Engineers to court to prevent it, but were unsuccessful.

Farther downriver is the Morganza Spillway, which runs from the town of Morganza along the Mississippi and guides water into the Atchafalaya Basin, with guide levees some 20 miles apart channeling water toward the gulf. The Atchafalaya Basin is a huge swamp surrounding the Atchafalaya River. Levees surround the basin, and ring levees surround some of the towns inside of it, but opening the Morganza means there’s going to be lots of flooding within the basin, and many homeowners are at risk.

Obviously I sympathize for the people in the Atchafalaya Basin. But I steadfastly reject the idea that we shouldn’t have opened the Morganza Spillway. Opening the Morganza is a last-ditch strategy, and one that is rarely called for. In fact, the only other time it was ever opened was 1973 (contrast that with the Bonnet Carré, which has been opened ten times). And the people know that they are living in a floodway, albeit a seldom-used one. Because it is so large and so rarely used, there is some development within it, as opposed to the smaller, more frequently-opened Bonnet Carré. And while one hopes that the Morganza will be opened as rarely as possible, when it is opened, that is only because it is in the best interests of the state and the nation as a whole.

The Mississippi River from Baton Rouge through New Orleans to the Gulf of Mexico is a vitally important corridor of industry, with refineries galore, petrochemical factories, and four of the country’s thirteen largest ports. Flooding along this stretch of the river would be bad, of course, but there is a far greater risk involved, one which would have been heightened by not opening the Morganza. That risk is the possibility of the Mississippi changing its course to follow the Atchafalaya.

Rivers in their natural state will roam all over, depositing sediment to new places, meandering back and forth, forming oxbow lakes and different channels. Water runs downhill, and it wants a steep path. Right now, the path along the Atchafalaya River is much, much steeper than the path along the Mississippi. If Mother Nature had her way, the fury of the Mississippi would roar down the Atchafalaya, reducing the flow of the Mississippi to a relative trickle.

So what’s stopping this from happening? The Old River Control Structure, named for what people called the “Old River.” Formerly part of the main course of the Mississippi, the Old River was bypassed when steamboat captain Henry Shreve (namesake of Shreveport) cut off a meander of the river to create a shorter path. The Old River then connected the Mississippi with the Red and Atchafalaya Rivers to the west. (Lots of details about this are available here.) Water could flow in either direction depending on the relative levels of the river, but by the mid-20th century it was clear that if nature remained unchecked, the Mississippi would switch its course to the Atchafalaya. Thus, the Old River Control Structure was built. Completed in 1963, it allowed the Corps of Engineers to control the amount of water flowing into the MIssissippi and Atchafalaya, and it was decided that 70% of the flow should go to the Mississippi, with the other 30% going to the Atchafalaya. It’s done its job so far, but in 1973 the structure was damaged by that year’s flood. In 1986 the Auxiliary Structure was completed to alleviate pressure on the rest of the system.

So what would happen if the Mississippi shifted its course? It would be a horrific disaster. Let me put it this way: I grew up scared of The Big One, the powerful hurricane that would strike New Orleans. Now I’m more scared of the failure of the Old River Control Structure. The most direct effects would be felt in the Atchafalaya basin, with massive flooding, damage to bridges and pipelines, and so forth. But the long term effects on Baton Rouge and New Orleans would be worse. The cities’ major source of fresh water would be gone, with water from the gulf turning the river into a brackish estuary. Shipping would be disrupted—remember how I said we have four of the largest ports in the country? Factories would be devastated, and life as we know it would be gone. The nationwide impact would be enormous. The energy, chemical, and food industries would be directly affected, while the interruption of the ports’ normal operations would affect giant swaths of the American economy—imports from Latin America and Asia, exports of grain traveling from the Midwest. Just as New Orleans is vulnerable to hurricanes, it is vulnerable to the vagaries of the Mississippi River. But the city’s value makes it worth defending from both of those threats. Given the significance of the Old River Control Structure, it is obvious that the Corps made the correct decision in opening the Morganza.

For additional reading, I suggest these links:

http://www.wunderground.com/blog/JeffMasters/show.html
A brief discussion of the possibility of course change.

http://www.newyorker.com/archive/1987/02/23/1987_02_23_039_TNY_CARDS_000347146?currentPage=all
A lengthy article about the river, its history, and the people who call the Atchafalaya Basin home.

I also highly recommend John M. Barry’s book Rising Tide, which you can probably find fairly cheap at a bookstore. (I think I picked mine up off a discount shelf at Barnes & Noble for $5 or so.) It focuses on the 1927 Mississippi River flood, delving into the history of man’s attempt to control the river and the competing theories about the best means of doing so; it also discusses the upper-crust of New Orleans society and Senator LeRoy Percy’s role in the politics of Mississippi. Barry’s website features this essay about the importance of New Orleans.