WI: The Old River fails; Atchafalaya captures the Mississippi

[QuoProQuid]

For about a century and a half, the United States Army Corps has been engaged in a slow motion battle with Mother Nature. The Mississippi River with its sand and silt has created most of Louisiana. It could not have done so by remaining in one channel. Instead, for most its history, the river has meandered across an arc about one hundred miles wide. Recently, pressure has built within the Mississippi to divert its course. If allowed to flow naturally, the water would jump the bank from its current position into a little known distributary called the Atchafalaya River.

For the Mississippi to make such a change is normal. Unfortunately, the United States cannot afford normal. The consequences of the Mississippi diverting would include the loss of fresh water and trade from New Orleans. The ports of Baton Rouge would become silt bars. Morgan City would find itself underwater in hours. It would reap untold economic devastation onto the American South.

Louisiana is protected from catastrophe by the Old River Control System, a system of floodgates in Central Louisiana. In 1973, however, the system almost did fail during a Mississippi flood. Large scour holes formed on both sides of the control structure. Had they met, the entire system would have collapsed and the Mississippi suddenly would have returned to its natural course.

So, what if in April 1973 the two holes had met? What would be the social, economic and political ramifications?

 

[Riain]

I wondered the same thing in January, this is the discussion.

https://www.alternatehistory.com/discussion/showthread.php?t=265970

 

[The Doctor]

Be interesting to see this idea constituted into a timeline or have more discussion here as that other linked thread kind of ends.

 

[thekingsguard]

Given the calls to allow more inflow to help preserve the Bayou, maybe the enviromental movement calls for a transition?

 

[QuoProQuid]

Given the calls to allow more inflow to help preserve the Bayou, maybe the enviromental movement calls for a transition?

What do you mean by this? The course of the river would change suddenly and without warning.

 

[Carl Schwamberger]

I see several imeadiate outcomes. 1. The crisis would inevitably affect the US Presidency and the 1976 election.

2. The business community in New Orleans would be frantic to have the channel restored and exert every effort to that end, no matter how unrealistic.

3. Grain prices globally would become 'volatile' as the primary outlet for US grain exports is disrupted.

4. Internally transport and port prices would be come volatile as well as alternate export routes are sought. Farmers would be looking at price volatility as well.

5. Food wholesalers, retailers, consumers, and commodities brokers would be seeing panic buying/selling and of course price vola...

All that will take off in the first few days. Despite the lack of a internet bad news spread with the speed of light in 1974 and the markets will hardly lag behind this event by 24 hours, in some cases the sort of price volatility mentioned above will be seen in one to six hours of the catastophe being understood nationally.

Then there are the long term effects...

 

[Carl Schwamberger]

Quote:
Originally Posted by thekingsguard
Given the calls to allow more inflow to help preserve the Bayou, maybe the enviromental movement calls for a transition?

What do you mean by this? The course of the river would change suddenly and without warning.

He must mean something that should be considered now or in the future?

 

[Captain Jack]

I thought he meant that there would be calls for a transition between the two courses with the river only partially diverted back to its current course.

 

[Mad Bad Rabbit]

So, what if in April 1973 the two holes had met? What would be the social, economic and political ramifications?

My view, from A Very Bad Year (1973):

Immediate impacts:
- Morgan City destroyed, over a thousand people drowned.
- All road, rail, and pipeline crossings south of the ORCS are washed out
- - Traffic has to detour hundreds of miles north via Natchez or Vicksburg.
- - Broken pipelines cause nationwide disruptions in natural gas supplies.
- The Gulf Intracoastal Waterway is closed at the Atchafalaya.

By late summer:
- Brownouts along East Coast, as peaking power becomes unavailable due to natural gas shortages.
- Ammonia fertilizer shortages (also due to natural gas shortages) ahead of fall planting.
- Old River channel is down to 1/4 of normal flow, and has to be closed to barge traffic.
- Atchafalaya channel is still much too turbulent and dangerous for navigation

By fall harvest:
- Lack of fertilizer and shipping (plus previous Soviet buying) leads to massive spike in grain prices and worldwide unrest.
- Lack of cooling water forces refinery and chemical plant shutdowns along Old River channel.
- - Shortages and price increases for all petrochemical-based products, from gasoline and diesel fuel to housepaint and insect spray.

The shortages and price spikes will play hell with the Nixon Administration's attempts at wage and price controls.
The blackouts and economic instability will probably spark riots (especially in New Orleans, where a third of the workforce has been
temporarily laid off, and water rationing is in effect).

 

[Orville_third]

Could this be possible in a Katrina scenario?

 

[Carl Schwamberger]

It is possible in any scenario that combines severely heavy rain fall in the Mississippi basin and miscalculation by flood control engineers. The rainfall must cause severe flood at the barrier to the Atchafalaya. That implies a lot of rain up stream. A hurricaine would not itself dump enough rain that far north. The juncture of the Atchafalaya Mississippi is too far from the coast to be affected by the sort of tidal surge that drowned New Orleans a few years ago.

 

[QuoProQuid]

Could this be possible in a Katrina scenario?

You need severe flooding up north. The reason the scour holes opened up in 1973 is because of debris that dug into the bottom of the riverbed. The Mississippi is at risk whenever the North has a particularly bad winter.

All the levees and anti-flood designs around the former path of the Mississippi will have suddenly been rendered unnecessary. The government will have to rebuild these along the Atchafalaya before the end of winter or risk further loss of life and property.

For the Nixon administration, the failure of the Old River Control System happens at the worst possible time. He's lost his top advisers, individuals who would have helped the President develop an appropriate response. The only positive for Nixon is that the disaster might overshadow the ongoing investigations against him. It will also probably force the media to come up with a different name than "Watergate".

 

[BlondieBC]

I see several imeadiate outcomes. 1. The crisis would inevitably affect the US Presidency and the 1976 election.

2. The business community in New Orleans would be frantic to have the channel restored and exert every effort to that end, no matter how unrealistic.

3. Grain prices globally would become 'volatile' as the primary outlet for US grain exports is disrupted.

4. Internally transport and port prices would be come volatile as well as alternate export routes are sought. Farmers would be looking at price volatility as well.

5. Food wholesalers, retailers, consumers, and commodities brokers would be seeing panic buying/selling and of course price vola...

All that will take off in the first few days. Despite the lack of a internet bad news spread with the speed of light in 1974 and the markets will hardly lag behind this event by 24 hours, in some cases the sort of price volatility mentioned above will be seen in one to six hours of the catastophe being understood nationally.

Then there are the long term effects...

Not that bad for Port on New Orleans. River surface is only 7 feet or so above sea level, and channel is 60+ feet. Lake Ponchitrain is 4 feet. Probably only lose a couple feet of elevation on river. Little extra dredging for CoE. Most stuff goes to RR pretty quick if unloaded. Chemical plants may have issue. But probably fixable long-term with more dredging.

Now the immediate problem is you probably can't get bulk goods (grain) from midwest to port of New Orleans or various other related terminals without using rail. It will be fixed in a year or two, one way or another, but we do see major export bottleneck. CoE has a lot of work to do. This is a no budget limit project.

Now we could see things like famine in places. Can't give you world food situation that year. We could see a lot of it rot, since I doubt we have enough storage for a full year grain crop, sitting idle. And it was wet year, so above ground, outside storage does poorly.

And we see the delta of the Mississippi decline in size faster than OTL, and build up near new river channel.

 

[Carl Schwamberger]

And we see the delta of the Mississippi decline in size faster than OTL, and build up near new river channel.

I wonder if the delta along the Mississippi channel would decline fast enough to allow a Katrina size storm surge around New Orleans a decade or more earlier?

 

[QuoProQuid]

Just one bump.

 

[Mike Stearns]

What do you mean by this? The course of the river would change suddenly and without warning.

I think what he means that the river's course is going to eventually shift regardless, but with planning you can manage the transition and ensure minimum disruption.