2019 Mississippi River

[angeleast]

May be a stupid question... but would water have any possibility of reaching Lafayette in worst case scenario????

not stupid.. I want to know too

[gorcajun]

Rising Tide: The Great Mississippi Flood of 1927 and How It Changed America by John Barry might provide some interesting information

[CajunRebel]

I suppose the worst case scenario would be a repeat of the flood of 1927, which reached right up to Lafayette, but didn't flood it. Almost all of St. Martin Parish was underwater. Of course Lafayette is much bigger now, so there may be some lower lying areas, or areas around the Vermillion that might be flooded.

I'm pretty sure there would have to be some massive levee failures for this to happen.

The green is what flooded in 1927.

[HelmutVII]

May be a stupid question... but would water have any possibility of reaching Lafayette in worst case scenario????

No.....The worst case is getting to the base of the coteau ridge. The coteau ridge is very prominent in the area if you know where to look for it. Starting in the south you can see it at Spanish lake north of new Iberia. Traveling east from Broussard to St. Martinville you will go down a hill about a mile east of 90. Highway 90 at the vermilion river is a cut in the ridge, as is Surrey street. If you have ever been to Oakbourne country club you are traveling on the edge of the ridge as you enter the gate. The new UL Golf practice facility is built on the edge of the top of the ridge. Traveling on the old breaux bridge highway you go down a fairly large hill right before the turn off on the Cypress Island road. This is the historic location of the edge of the 1927 flood. My father and uncles volunteered to help rescue people in Breaux Bridge during that flood. The water wasn't too deep as they used national guard trucks to evacuate people. As you travel east on I 10 you will go down a very pronounced hill and traverse a cut in the ridge just east of the Moss street over pass. If you travel east on Pont Des Mouton, Butcher Switch and Gloria Switch from Moss street you will travel down a very pronounced hill. But the most classic example is the over look you get on I-49 near Doctors Hospital in Opelousas. Look to the east and you will see what was the edge of the Mississippi river over 10,000 years ago. There are cattle grazing on that property most of the time. Highway 190 just east of Opelousas going to Port Barre is another pronounced cut. I 49 north of 190 heading to Washington is very hilly and that is the Coteau Ridge.

Once you get north of Washington on I 49 you will get to and travel through the Pleistocene era Mississippi flood plain. There is a reason why I-49 is built up on about a 20 foot embankment. The fill for the embankment was obtained from the lake that was created at the rest area on the east side of I-49 about 4 miles north of La Highway 10 exit. This is called Dubuisson Lake and was a 640 acre lake purchased from Nick Dubuisson in the late 1970's for the borrow pit. The coteau ridge veers to the north and west north of Washington.

On a side note. The Contractor that did the embankment work on the Interstate was from either Minnesota or Wisconsin so they didn't know too much about floods. They were leaving one weekend in the spring for a few days off. An Old guy that lived on the access road to the pit told the guys "you better get you machines out of dat pit". They asked him why. He said "De flood is coming". They said "what flood" The old guy said "it's going to be here in about 2 to 3 days." They thought he was crazy. When they came back about four or five days later only the top parts of the booms of the drag lines were sticking above the water and every other piece of equipment was under water. It took them 6 MONTHS after the flood receded to pump the water out of the pit.

[HelmutVII]

As well as altered stream hydrology not allowing for normal deposition.

While that may be true to a degree. It was found after the Kat-Rita event of the fall of 2005 that the entire portion of South Louisiana from Mississippi to the Texas border and beyond was in a generalized subsidence area. From Lafayette west subsidence varied from 0.5' to 1.5 feet. Subsidence was most pronounced in areas where heavy ground water pumping was taking place by rice farmers. Lafayette area was 0.5 feet to 0.8'. To the east of Lafayette through the basin and over to New Orleans it was more pronounced as the geologic age of the land was very small and was never really stabilized prior to human habitation and development. Subsidence is more than 2.0' in many places. That was one of the reasons why FEMA and the USC&GS decided to void all published elevations for bench marks and require all elevation work with respect flood zone work and Flood elevation certificates to be perform using GPS observations. I know that for a fact because I had to purchase over $20,000.00 in equipment to perform that work. All flood certificates and flood studies to this date are done using GPS observation using the latest GEOID.

So even though the levees are blocking natural soil deposition, the main culprit is subsidence in the eastern portion of the state. That along with storm surge that basically washes away the barrier islands makes it a multi faceted problem that in many ways cannot be solved because it is very difficult to fight subsidence.

Last I heard subsidence was at the rate of about 0.5 to 1.5 centimeters per year. Our GPS equipment is sub centimeter accuracy.

This publication by the USGS might be helpful

https://pubs.er.usgs.gov/publication/70028078

[CajunJeaux]

No.....The worst case is getting to the base of the coteau ridge. The coteau ridge is very prominent in the area if you know where to look for it. Starting in the south you can see it at Spanish lake north of new Iberia. Traveling east from Broussard to St. Martinville you will go down a hill about a mile east of 90. Highway 90 at the vermilion river is a cut in the ridge, as is Surrey street. If you have ever been to Oakbourne country club you are traveling on the edge of the ridge as you enter the gate. The new UL Golf practice facility is built on the edge of the top of the ridge. Traveling on the old breaux bridge highway you go down a fairly large hill right before the turn off on the Cypress Island road. This is the historic location of the edge of the 1927 flood. My father and uncles volunteered to help rescue people in Breaux Bridge during that flood. The water wasn't too deep as they used national guard trucks to evacuate people. As you travel east on I 10 you will go down a very pronounced hill and traverse a cut in the ridge just east of the Moss street over pass. If you travel east on Pont Des Mouton, Butcher Switch and Gloria Switch from Moss street you will travel down a very pronounced hill. But the most classic example is the over look you get on I-49 near Doctors Hospital in Opelousas. Look to the east and you will see what was the edge of the Mississippi river over 10,000 years ago. There are cattle grazing on that property most of the time. Highway 190 just east of Opelousas going to Port Barre is another pronounced cut. I 49 north of 190 heading to Washington is very hilly and that is the Coteau Ridge.

Once you get north of Washington on I 49 you will get to and travel through the Pleistocene era Mississippi flood plain. There is a reason why I-49 is built up on about a 20 foot embankment. The fill for the embankment was obtained from the lake that was created at the rest area on the east side of I-49 about 4 miles north of La Highway 10 exit. This is called Dubuisson Lake and was a 640 acre lake purchased from Nick Dubuisson in the late 1970's for the borrow pit. The coteau ridge veers to the north and west north of Washington.

On a side note. The Contractor that did the embankment work on the Interstate was from either Minnesota or Wisconsin so they didn't know too much about floods. They were leaving one weekend in the spring for a few days off. An Old guy that lived on the access road to the pit told the guys "you better get you machines out of dat pit". They asked him why. He said "De flood is coming". They said "what flood" The old guy said "it's going to be here in about 2 to 3 days." They thought he was crazy. When they came back about four or five days later only the top parts of the booms of the drag lines were sticking above the water and every other piece of equipment was under water. It took them 6 MONTHS after the flood receded to pump the water out of the pit.

Thanks for such a detailed response, your knowledge is impressive...regarding property in opelousas east of the hospital, i had heard before that that was once the MS River...beautiful piece of property

[HelmutVII]

I’d be willing to bet that they open the Morgansa Spillway. We have tremendous floodwaters headed out way from upriver. Opening the Bonnet Carre isn’t going to relieve enough pressure on the river.

The magic number is 1.5 to 2.0 feet per second velocity of the water near the levees That velocity will start scour of the levees and "balling" of the grass and vegetation protecting the levees. No vegetation on the levees could result in levee failure.

[mahtoo]

Anybody have any thoughts/news about the River, the subject of the thread, not related to politics, religion or any other completely unrelated tropic?

We're in for a rough spring/early summer. IMO will be worse than 2011.

[mahtoo]

I’d be willing to bet that they open the Morgansa Spillway. We have tremendous floodwaters headed out way from upriver. Opening the Bonnet Carre isn’t going to relieve enough pressure on the river.

I suspect you're right about Morganza. And opening Bonnet Carre will help with river stages below that structure, not reaches above Bonnet Carre except for the near vicinity of BC due to a drawdown effect.

[cajun4life]

The magic number is 1.5 to 2.0 feet per second velocity of the water near the levees That velocity will start scour of the levees and "balling" of the grass and vegetation protecting the levees. No vegetation on the levees could result in levee failure.

I believe that will be a major issue this time around. The levees are saturated already and the continued high water could lead to sand boils. Although a levee breach is much less likely than before, it’s still a possibility.

[CajunNation]

As usual, great info Helmut. Thanks.

[Cajun90]

I believe that will be a major issue this time around. The levees are saturated already and the continued high water could lead to sand boils. Although a levee breach is much less likely than before, it’s still a possibility.

I think it was 2011 when there were concerns with the levees around Angola. On top of all the other concerns can you imagine having to move over 6000 prisoners; many of whom are dangerous. After all you don't end up in Angola for jaywalking.