As we all know by now, the U.S. Army Corps of Engineers began opening the Morganza Spillway in Morganza, Louisiana, yesterday. This is a drastic step, but a necessary one to protect the levees, engineering structures, and the Major port cities of Baton Rouge and New Orleans. There is a lot of coverage of the opening in today’s news because 1) this man-made flood will affect a lot of lives and property; and 2) it is a rare event.
In the past several days, I’ve read some rather interesting questions concerning the opening of this particular spillway. Most of them came from concerned citizens who are in harm’s way down there in Terrebonne Parish.
Here’s one question that caught my attention. The Morganza Spillway has only been opened one time, and that was 38 years ago. At least one person was concerned that they wouldn’t be able to close it once it was opened.
This isn’t some crazy notion. If you’re familiar with the lower Mississippi, you’re probably aware that the river “wants to go that way” anyway. In the natural, non-engineered world, rivers like the Mississippi meander quite a lot, and this one has a tendency to want to meander right through the Atchafalaya basin by merging with the Atchafalaya River, instead of following its present course. To prevent it from doing that, an ingenious piece of engineering was done by building the Old River Control Structure, (the ORCS), in 1975. This dam-like structure blocks the river from going the way it wants to go. But this historic flood is testing the ORCS like never before. The engineers are reassuring everyone that it will hold, but if it doesn’t, there will be a disaster with a capital “D.” The river will have its way after all.
The Old River Control Structure complex. View is to the east-southeast, looking downriver on the Mississippi, with the three dams across channels of the Atchafalaya River to the right of the Mississippi. Concordia Parish, Louisiana is in the foreground, on the right, and Wilkinson County, Mississippi, is in the background, across the Mississippi on the left. From Wikipedia.
So that’s part of the concern about opening the Morganza Spillway. The river “wants to take” the shortest route to the Gulf of Mexico, and that route is right through the Atchafalaya Basin. Maybe that is why they decided not to open all the bays of the spillway. I’m glad I’m not the one who has to make decisions like this.
The second good question I read was that since the spillway has not been opened in 38 years, how do they know the basin still has the same capacity it had 38 years ago. One person claimed with great certainty that the basin is shallower now. Here’s hoping they’ve done some recent land surveys to make sure the water is going to go where they intend for it to go.
Wikipedia’s map showing existing channels, probable new channel, and levees.
These two questions will be answered in due time. Like the drought in Texas, this is a sort of slow-motion disaster that plays out a little bit at a time.