WI Missisippi changes course?

Apparently there is a view among those who control the Missisippi that it wants to go west and flow out through the Atchafalaya River, which would bypass Baton Rouge and New Orleans. This could happen if a flood was bad enough and overcame the flood control measures.

So WI the flood control measures broke and the Missisippi's main outflow went through the Atchafalaya River?
 

BlondieBC

Banned
It is a when, not if. As slit builds up, the pressure to move to a new channel increase a little each year. There have been at least 7 river beds in the last 10K years.

Now to what happens. Morgan city is lost. The infrastructure to support the oil industry has to be rebuilt, probably just at a higher elevation. Painful but manageable. The Mississippi at NO is only 7 feet above sea level, so the port will be kept open with dredging, just as now. NO needs a new water source, but fixable with cash. The swamp below the city will start to "waterfy" faster than now since it lose the silt coming in. Man's activities have reduced it, but not eliminated silt deposits each year. New land will start to form at the new mouth. Very bad, but manageable. Now if you get an unexpected failure, you could lose 20K people, but likely there will be warning since it is most likely at a very high flood stage.
 
All in all, expensive but manageable in it's own right, effectively the same as what it takes to keep it where it is. The really scary scenario would be another major New Madrid earthquake, aside from everything else this would trigger there is a very good chance the river could shift almost instantly, and in the middle of what is probably going to amount to generalized chaos.
 
The sensible answer when it was discovered this was going to happen would have been to design a system to manage a slow shift of the main flow to the new channel, so that measures adapting to the new behavior could be implemented relatively gradually and cheaply, rather than try to permanently prevent it with things like the Old River Control Structure. I don't know why the Corps of Engineers didn't do this.
 
Would the money be spent on NO, or would the change be accepted as fact and NO left to wither? Perhaps the money could be better spent on building up infrastructure on the new course.

BTW this could probably go into Future History since it hasn't happened yet, only threatened to a couple of times.
 
Apparently there is a view among those who control the Missisippi that it wants to go west and flow out through the Atchafalaya River, which would bypass Baton Rouge and New Orleans. This could happen if a flood was bad enough and overcame the flood control measures.

So WI the flood control measures broke and the Missisippi's main outflow went through the Atchafalaya River?

As stated above, when not if. If memory serves, there is a dam preventing a major change of flow. Said dam is already undermined and some day the river is going to move, with or without the permission of the Army Corps of Engineers. When it does, there are a LOT of people downstream.
 
The sensible answer when it was discovered this was going to happen would have been to design a system to manage a slow shift of the main flow to the new channel, so that measures adapting to the new behavior could be implemented relatively gradually and cheaply, rather than try to permanently prevent it with things like the Old River Control Structure. I don't know why the Corps of Engineers didn't do this.

I suppose it's because New Orleans, a massive port of great strategic importance, is currently downstream. No longer being downstream would render it pretty useless. Also the diaspora that would have resulted along the new course would have been a costly disruption in its own right.

Believing that they could fight Nature and win may turn out to be unfounded arrogance; time will tell. Personally, I'm betting on Nature.
 
According to Wiki the Atchafalaya River does have significant industrial shipping, would this be enough to forestall a major recession after a course change? What about the old course, surely it won't just die? Would it stay open for less than 50% of the flow and remain a shipping channel in the 18 or so months after the flood which causes the change?
 
I suppose it's because New Orleans, a massive port of great strategic importance, is currently downstream. No longer being downstream would render it pretty useless. Also the diaspora that would have resulted along the new course would have been a costly disruption in its own right.

Believing that they could fight Nature and win may turn out to be unfounded arrogance; time will tell. Personally, I'm betting on Nature.

Well, that's why I said make a slow and controlled change. For instance, if you conducted a 1% course change per year (such that 0% means the current situation and 100% means whatever a diverted Mississippi would look like), it would take a century to actually make New Orleans useless. That's far more than enough time for facilities to relocate to the new delta region, rebuild infrastructure accounting for the new channel, and so on. Already they divert 30% of the Mississippi's flow down the alternate stream, actually.
 

BlondieBC

Banned
The sensible answer when it was discovered this was going to happen would have been to design a system to manage a slow shift of the main flow to the new channel, so that measures adapting to the new behavior could be implemented relatively gradually and cheaply, rather than try to permanently prevent it with things like the Old River Control Structure. I don't know why the Corps of Engineers didn't do this.

The corp has more of a "conquer nature" mentality than "work with nature".



Then you can get to the details of what it means. Manageable is not cheap. So once you decide to do it, the real go point is appropriating a huge amount of money (I would guess 200 billion USD) to start the five year process. Morgan city is not large, but it is critical. It is where much of what supports the off shore industry is located. It would have to be rebuilt somewhere else. Imagine trying to explain at the last Presidential debate why Obama "gave the oil companies 50 billion and produced no new oil". You would have to dredge down about 120 miles of river by 7 feet. This is 7 feet by 1500 feet wide by 120 miles. Lot of dirt. Build pipe line to bring in water to city of 1 million (NOLA). Not sure where this comes from, put probably water intake north of Baton Rouge. Then some dry summer (lower water time), you would need to start diverting the water. Few % at a time. It needs to be slow so you don't mass drown the wild life. And you will have to dredge out new ship channel to Ocean from the diversion point to the ocean. You may need to build temporary locks to bypass the dam. And I would guess that in this process of the actual diversion (3-9 months??), you can't take any ship from St. Louis to the ocean ports. Have to think how you get one years grain harvest to world markets.

All of this is doable. Corp is good organization. But it is always the easiest call to say "not in the next few decades".
 

BlondieBC

Banned
Would the money be spent on NO, or would the change be accepted as fact and NO left to wither? Perhaps the money could be better spent on building up infrastructure on the new course.

BTW this could probably go into Future History since it hasn't happened yet, only threatened to a couple of times.

If you want it moved, just petition it.

NOLA is not hurt, once you get the water. The water depth at New Orleans is over 60 feet. The water height is only 7 feet above sea level. New Orleans is still a port, if you do the dredging. Might even be better port since I might cut a shorter path to sea now that river will not refill. And there is an issue on sewage. Have to build pipes to dump farther from the city. NOLA is cut off from river cycle (silt) by levee. No change. Now we will start to see the swamps die faster, but new land will be built at new mouth. It is more places like Venice that are at risk, but I would guess it would turn into an Island over time.

And there will be a huge amount of new infrastructure. The port of NO can still unload stuff for RR. The chemical plants are fine. But you have to now move grain to new port. Probably Port of Fourchoun. Not sure if they ever got around to building it.
 

BlondieBC

Banned
Well, that's why I said make a slow and controlled change. For instance, if you conducted a 1% course change per year (such that 0% means the current situation and 100% means whatever a diverted Mississippi would look like), it would take a century to actually make New Orleans useless. That's far more than enough time for facilities to relocate to the new delta region, rebuild infrastructure accounting for the new channel, and so on. Already they divert 30% of the Mississippi's flow down the alternate stream, actually.

No can do. Can't get grain to market. This will starve millions in areas of world. Water is the only practical way to move this much weight to markets in other continents.
 
No can do. Can't get grain to market. This will starve millions in areas of world. Water is the only practical way to move this much weight to markets in other continents.

o_O. So, over a century-long period they can't build new port facilities? Add rail "bridges" (in the sense that the Panama rail line, before they built the canal, was a bridge) to move grain over the now-dewatered sections? Because, you know, I'm pretty sure most of the physical facilities of the Port of New Orleans are less than a century old (even if the port itself is, of course, much older).

The whole point of managing the change slowly and gradually is so that problems like this can be dealt with instead of continually building up the existing facilities so that when the Mississippi changes course you have a crisis like half the world starving because major transshipment points for US grain are now useless. And I really, really, really doubt that shifting 0.06% of the Mississippi's flow per month (or 0.002% per day) is going to cause ships to be unable to navigate the Mississippi all of a sudden. (And this is assuming that a "diverted" Mississippi would have a 100% flow down the Atchafalaya River, rather than, say, simply reversing the present 70/30 split so that the minority flows down the present channel. If you did that, you would be diverting 0.001% per day). Given a high-end mean annual flow for the Mississippi, about 20,000 m^3/s (according to Wikipedia), this would mean changing the amount of water moved by the main channel in a day by about 17-18000 cubic meters, on average. This sounds like a lot of water, but it's about the same volume as a cube 25 meters on a side. It's less than a second of the river's discharge flow. It really isn't significant to navigation.

The corp has more of a "conquer nature" mentality than "work with nature".

Well yeah, of course.

Then you can get to the details of what it means. Manageable is not cheap. So once you decide to do it, the real go point is appropriating a huge amount of money (I would guess 200 billion USD) to start the five year process.

Well no, it's not cheap. What's also not cheap is fighting nature the way the corps does. What's also not cheap is having tens of billions of dollars in investments go down the drain because you chose to fight a battle you were inevitably going to lose rather than start a long-term process to mitigate it, like I proposed.

Given that I was talking about a 100-year process, too, it wouldn't cost nearly that much. Most of the actual funding would come in routine spending, where you would build or repair existing infrastructure to fit the planned limits or private industry would build new facilities in new locations rather than reconstructing old facilities which will become useless. That's the whole point of doing it gradually, you don't need to spend hundreds of billions or trillions of dollars to make the changes because your intent to do so spurs, well, markets to do a lot of that spending instead, or local government.

Morgan city is not large, but it is critical. It is where much of what supports the off shore industry is located.

Fair enough, but there are other ports that are major offshore support bases, like the Houston/Galveston/Texas City area, or the Beaumont area. And, again, this is supposed to be a gradual process, so all this investment won't be irrelevant at once. Instead, what would happen would be the relevant corporations choosing to invest in facilities elsewhere while they work out their equipment in Morgan City. Or just in different parts of Morgan City, where the enlarged flow won't actually have a negative effect.

You would have to dredge down about 120 miles of river by 7 feet. This is 7 feet by 1500 feet wide by 120 miles. Lot of dirt. Build pipe line to bring in water to city of 1 million (NOLA). Not sure where this comes from, put probably water intake north of Baton Rouge. Then some dry summer (lower water time), you would need to start diverting the water. Few % at a time.

You know, if you actually read what I wrote, it would help. I was envisioning a much, much longer-term process, not merely a controlled version of the "flood breaches Old River Control Structure" scenario. Of course if you do that you have to spend a lot of money and go to a lot of trouble--that's why you don't do that! So you dredge out that area by slightly increasing the amount dredged routinely, so that over time all that extra volume will be taken out. You don't spend billions of dollars on relocating oil refineries and chemical plants and so on, you tell ExxonMobil and BP and Total and all them that, well, in fifty years or so it's going to be real hard to reach those plants, so they might want to think about spending on building new ones rather than upgrading existing ones. You don't need to make special arrangements for shipping grain for one harvest, or at worst you need a relatively short rail bridge from the branch point to the new terminals at Morgan City or thereabouts. Nice, gradual, not horribly expensive, not the result of a disaster.
 
While it would be great to start developing the other distributary nnow and then plan to move to it, from thhe limited reading I've done you might not get that chance. That's what I'm interested in, the sudden paradigm shift flood and couple of years afterward.
 
While it would be great to start developing the other distributary nnow and then plan to move to it, from thhe limited reading I've done you might not get that chance. That's what I'm interested in, the sudden paradigm shift flood and couple of years afterward.

Here's the disaster study I used in "A Very Bad Year (1973)" :

Kazmann, Raphael G. and David B. Johnson. 1980. "If The Old River Control Structure Fails?"

http://www.lwrri.lsu.edu/downloads/L...I_B12_1980.pdf
(section beginning at page 101)
 
Considering the amount of dredging and other maintanence for naviagation's sake, wouldn't it take a major event to change the course nowadays, at least concerning a rapid change.
 
Well, that's why I said make a slow and controlled change. For instance, if you conducted a 1% course change per year (such that 0% means the current situation and 100% means whatever a diverted Mississippi would look like), it would take a century to actually make New Orleans useless. That's far more than enough time for facilities to relocate to the new delta region, rebuild infrastructure accounting for the new channel, and so on. Already they divert 30% of the Mississippi's flow down the alternate stream, actually.


I suppose we'd need an engineer to say for certain, but such a gradual series of changes might not be possible. The basic technology is still the static dam, and even a small dam (which the Atchafalaya project isn't) is a huge project. Build one, then another, then another? I'm not sure what you have in mind as a means for gradual change.
 
mrc_map.gif


Hmm I wonder if New Orleans was held by a foreign power (Britain France or Spain) if it would be feasible for the USA to dig a channel to devert the Mississippi.

If you look on this map you can see what is stopping the Atchafalaya taking a greater share of the water is that joins against the flow. However the Red River that flows into the Atchafalaya runs about 5 mile from where the Mississippi has a tight bend so a canal at the right angle would be flushed clear and capture maybe half of the rivers flow.
 
I suppose we'd need an engineer to say for certain, but such a gradual series of changes might not be possible. The basic technology is still the static dam, and even a small dam (which the Atchafalaya project isn't) is a huge project. Build one, then another, then another? I'm not sure what you have in mind as a means for gradual change.
Well, I'm not a civil engineer, but...how's this?

The amount of water that is allowed to bypass Old River Control and flow into the Atchafalaya is controlled by spillways gates. Open the gates a little bit more, and the Atchafalaya will pick up a bit more of the flow. During a "design flood" (the worst-case scenario for preventing a whole bunch of rain upstream from causing the Mississippi from overflowing its banks downstream), they'd dump 600,000 cubic feet per second into the Atchafalaya through the Old River Control Structure, which is pretty close to the non-flood average flow of the entire Mississippi . The river, as you can see here averages around 450,000 cfs, plus or minus about 200,000 cfs. So I think if they wanted to, they could do what truth is life is suggesting without needing a new river control structure.
 
Top