The recent flood is the highest since 1937-the width of the river (at memphis, TN) has tripled.
My question: given the enormous volume of water, why doesn’t the Missisippi break through to the Achafalaya River (at Baton Rouge), and find a new path to the Gulf of Mexico?
Probably because of the billions of dollars invested in the Lousiana river control structure, which was put in place to prevent that very thing.
The river is held in it’s current location by man-made structures. If it was just to take the path of least resistance, it would have rerouted itself.
In extreme flood stages like we’re having this year, there are additional measures taken to be sure the river doesn’t get out of control. The Bonnet Carré Spillway was opened this week to divert some of the water to Lake Pontchartrain, which will lower the crest at New Orleans by a foot or so.
On Saturday, they plan to open the Morganza spillway, just upriver from Baton Rouge, which will divert a lot of the water into the Atchafalaya basin, which eventually flows into the Gulf.
If the levees in New Orleans were compromised, I’m sure that the path of the Mississippi would change…it could possibly divert to where I’m sitting right now.
By opening the spillways, the amount of water flowing between Baton Rouge and the mouth of the river is reduced enough that the levees can handle it.
The answers have been given. It is modern marvel of engineering. The path of the lower Mississippi used to wander around abruptly over a huge area but we sealed it off so it isn’t easy for that to happen now. The earth works projects to make that happen are something to behold if you have never seen them yourself. I wonder if there is any remotely feasible scenario which would cause it to change course today and how that could be dealt with.
Someday the river will win this fight. I suspect it won’t be pretty, but I also think it’s inevitable.
I agree - it will be a mess. For additional reading about the Old River Control Structure and the Morganza Spillway I highly recommend Control of Nature by John McPhee.
Actually, engineers think that a really big flood might tip the river over into the Atchafalaya River, which is currently a minor distributary of the Mississippi. They’re worried that if that happens, it might be almost impossible to get it back on course. If it did jump its banks, it’d flood a lot of the area along the Atchafalaya and crash the economy of New Orleans. The current flood is straining the current system, but it’ll probably hold. However, it’s clearly possible that a flood could burst the control system and create a new river mouth.
New article today in Salon. It says that this year’s flooding is worse than in 1973 - when the river almost switched the main channel to the Actchafalaya. New engineering of the control structures was put in place then, sounds like this will be a real test of it.
This river needs an enema!
Imagine, NOLA becomes a backwater town-and the might Miss surges through to a new outlet!
One more link with a history of changes in the Mississippi channel… I’ll stop now.
And all the industry built along the lower Mississippi becomes inoperable overnight; leading to massive shortages and commercial disruption.
It’d be interesting to see New Orleans famous for its port and no longer having any river near it.
I’ve been watching the news about the thousands of homes, farms and business that are going to be flooded as the various spillways are opened. While I’m sympathetic to their plight, I don’t understand why someone would build their home in a spillway.
I’m not talking about the hundred year old mansion that was passed down for generations. Just those that have been built since the spillways were created. Any ideas?
They’re supposed to open the Morganza tomorrow.
Here’s a real concern. The Morganza spillway structure was built in the early 50s and only was opened once, in 1973, to relieve stress on the Old River Control Structure during the river’s spring crest.
Worst case scenario, they open the Morganza structure and as the water starts to go through, the whole thing collapses. At that point, a large percentage of the water starts flowing through the spillway. It’s the path of least resistance, much steeper than the current river.
Sediment would instantly start to build across the old river and would form a natural dam or levee.
At that point, they probably couldn’t get things back to the way they were before.
The Mississippi wouldn’t dry up in New Orleans, and the port wouldn’t cease to operate, although all of the traffic that goes up the river to points north would no longer pass through New Orleans.
The major problem would be that New Orleans would no longer have a source of drinking water. The water in (what we currently call) the river would be saltwater backwashed from the Gulf.
Sure everybody could start drinking bottled water, but when saltwater starts flowing into water heaters and iron bathtubs, things would start to corrode pretty quickly. Water would have to be piped in from the nearest fresh water river, which would then be about 100 miles away.
That’s ok…at the rate the coastline is eroding, New Orleans will be waterfront property soon anyway.
Because it only has basic cable.
THe mighty Miss meanders…in his classic “Life On The Mississippi”, Twain relates how the river was always changing its course…and how someday (jokingly) cairo, Ill. would be adjacent to New Orleans.
Ok, I lied. I have another link - New Yorker mag has brought the above mentioned McPhee article out from behind the paywall and anyone can read it. Worth a read.
I’ve been in the flood study business for 23 years. I have noticed that people like to live … where the like to live. 
Sometimes it’s a matter of “functionally dependent use”. Examples: a farmhouse needs to be located on the farm; a marina has to be located on the riverbank.
Sometimes it’s a case of a really nice area, or other family already living there, or a university which attracts people.
There is also a false sense of security given by levees, which kind of encourage people to build behind them. In theory, people are supposed to elevate their homes above the base flood elevation. In reality, if that’s a great height it can be seen as onerous, and local governments may grant variances, or may not enforce any restrictions on elevation.
Then you have the rarity of the event. This particular flood event has not been equalled or exceeded since 1937. Therefore, people don’t think about it happening.
Our State Floodplain Coordinator posed a video on his FB page yesterday showing some homes in Coahoma County which had been built with their finished floors 4.7 feet BELOW the base flood elevation. The County had granted them a variance.
One could propose that we should plan to * deliberately allow *the Atchafalaya to become the main outlet, and install new control structures to force a partial diversion of freshwater flow into an old Mississippi now turned into a canal (and build a proper aqueduct, while we’re at it; if we supply Los Angeles by aqueduct it should not be a major miracle to do so for New Orleans). But besides the large upfront expense, that would involve the political headache of on one side people claiming that the lower river is being “abandoned”, and on the other people saying “no bailout for NOLA!”. BTW a lot of the receeding shore problem is complicated by the very measures designed to keep the river commercially/industrially viable, as they prevent natural sedimentation.