This morning, the Mississippi River crested in Memphis, rising just shy of the all-time record height of 48.7 feet set during the great 1937 flood. The river, normally half a mile wide at Memphis, is now about three miles wide.
The only reason that this flood didn't set a new record was because the Army Corps of Engineers blasted levees and opened up two "floodways." The first was upriver, near Cairo, Illinois. As I wrote last week, this levee breach flooded thousands of acres of farmland in Missouri. (You can see incredible before and after satellite photos here.) While it seems like a tragedy for the Missouri farmers, in fact, flooding their land is exactly what's supposed to happen in this sort of storm. These floodways are part of the Army Corps' actual engineering plan. There's a reason the Army Corps calls this action "activating the floodway."
Earlier this week, the Army Corps opened up a second release valve—the Bonnet Carré Spillway, about 28 miles upstream from New Orleans. Here's a look at the Spillway when it's closed, in an Army Corps photo from 1999. When opened, water spills across that big rectangular field and into Lake Pontchartrain.
This Great Mississippi Flood of 2011 is a stark reminder to Americans of how the Mississippi River is not—and hasn't been for many decades—a naturally free-flowing body of water. It is, rather, a highly-engineered system of public works. (For the best piece I've ever read about how we try to wrestle these natural bodies into submission, read John McPhee's classic essay Atchafalaya.) And that highly engineered system is being tested by what Jeff Masters of Weather Underground describes as the "river's highest flood crest in history."
Masters explains what we can expect over the next couple of weeks.
Downstream from Memphis, flood waters pouring in from the Arkansas River, Yazoo River, and other tributaries are expected to swell the Mississippi high enough to beat the all-time record at Vicksburg, Mississippi by 1.3' on May 19, and smash the all-time record at Natchez, Mississippi by six feet on May 21, and by 3.2 feet at Red River Landing on May 22. Red River Landing is the site of the Old River Control Structure, the Army Corps' massive engineering structure that keeps the Mississippi River from carving a new path to the Gulf of Mexico...Its failure would be a serious blow to the U.S. economy, and the great Mississippi flood of 2011 will give the Old River Control Structure its most severe test ever.
In times like these, I can't help but think that we might have lots to learn from the Dutch, who have probably know the most about how to live with water. Four years ago, Dutch authorities came up with a water management plan called "Room for the River." Reversing generations of water control convention, the Dutch decided that rather than battle rivers with expensive dikes and levees and canals, they'd give rivers more room to flow freely. This video explains the program.
Here's the official "Room for the River" website.