2011 Mississippi River Spring Floods

[cajun_civil]

_ This is my favorite post so far, and says what I thought about a million times better than I did. Probably becuase it appears to have been written by a civil engineer who is an expert.

Cajun Civil, what is your take on the risk of the river changing course? (not necessarliy due to this event, but say if "project flood" ever actually happens) _

Charlie,
I am by no means an expert on the Mississippi River and it changing its course. I will say that in the micro view, man has controlled the mississippi. Will man always win? There is only one person I know who has the answer to that. In the interim, the men and women of my profession will continue the good fight using scientific data and sound engineering judgement.

BigEd, Jumbo, or Helmut your thoughts?

[cajun_civil]

_ Thanks for your post. I was just skimming through that report myself & according to page 6 I believe they do note that there was a scour hole that went down some 130' & passed from the upstream side of the structure to the down stream side of it. I may be misreading, but the guy I talked to said they pushing junk cars off barges to attempt to fill the sink holes below the structure. I am greatful that this has been addressed & it seems as though the ORCS is working fine. I am going to assume this based on the Atchafalaya cresting at Simmsport. I will read through this report & thank you for your comments & will welcome your corrections. The report is pretty long & I plan on downloading it to the computer for later reading.

I also thank Charlie for posting the info on the report. _

BK,
I just re-read the section of the report you are referring to. I agree that scour holes existed on each side of the structure, but I did not see where they were connected. I would anticipate that should a scour develop completley beneath the structure failure of the structure would likely occur.

You are correct in that cars and other debris were deposited in the area to help control the scour, i have no idea how effective those measures were.

I have seen solid boulders larger than pick-up trucks deposited in the Mississippi River during LOW FLOW conditions. In order to place the rock in the correct location, it was placed upstream of its final location.

The Mississippi is certainly more powerful and complex than most realize.

[Bandwagon King]

_ BK,
I just re-read the section of the report you are referring to. I agree that scour holes existed on each side of the structure, but I did not see where they were connected. I would anticipate that should a scour develop completley beneath the structure failure of the structure would likely occur.

You are correct in that cars and other debris were deposited in the area to help control the scour, i have no idea how effective those measures were.

I have seen solid boulders larger than pick-up trucks deposited in the Mississippi River during LOW FLOW conditions. In order to place the rock in the correct location, it was placed upstream of its final location.

The Mississippi is certainly more powerful and complex than most realize. _

Ok. I'm gonna ask another one of "those" questions. Why build a structure with an enormous total flow capacity when it can't be substained & can be undermined & destroyed ? Does anyone know why this structure was designed this way?

[HelmutVII]

_ Ok. I'm gonna ask another one of "those" questions. Why build a structure with an enormous total flow capacity when it can't be substained & can be undermined & destroyed ? Does anyone know why this structure was designed this way? _

The designers did not have the benefit of computer modeling, CAD software and many other modern design tools that we take for granted today. The design was done by a bunch of guys wearing black pants, neck ties and white shirts with a pack of Camels in the pocket. Their tools were slide rules, and drafting was done with triangles, and parallel bars. They sharpened their pencils with sand paper. Pretty primitive but they got the job done. Also, they did not have the body of knowledge then that we have today.

They built the structure with state of the art materials for that time. Materials that are no longer used today like grade 40 Rebar and 3000 psi concrete.

The only saving grace was that if they figured 1 foot 6 inches was enough they probably made it 2 feet 0 inches. Things were heavier, thicker and wider back then. Not necessarily bad just different.

If they would build the same structure today you might see the same scheme but executed totally different. Different foundations, stronger lighter steel and rebar, higher strength concrete, wider gates.

The design is not bad, actually it's was excellent then as it is now. After all, it is almost 90 years old and has worked 24/7 since it was placed into service.

[HelmutVII]

_ BK,
I just re-read the section of the report you are referring to. I agree that scour holes existed on each side of the structure, but I did not see where they were connected. I would anticipate that should a scour develop completley beneath the structure failure of the structure would likely occur.

You are correct in that cars and other debris were deposited in the area to help control the scour, i have no idea how effective those measures were.

I have seen solid boulders larger than pick-up trucks deposited in the Mississippi River during LOW FLOW conditions. In order to place the rock in the correct location, it was placed upstream of its final location.

The Mississippi is certainly more powerful and complex than most realize. _

There were scour holes on both sides but they were not connected, but it came pretty damn close. If they would have connected they would have lost the structure and the Mississippi would be going through Morgan city right now.

[HelmutVII]

_ biged:

Thanks again for all of the info-very interesting. Thinking about taking a drive this weekend to see as much of this stuff as I can-like taking a loop-driving 190 from Opel-then going over the Morganza spillway, then to the Old River Control Structure, back down and over the new Audubon bridge-then back to Lafayette on I-10 over the basin. Any recommendations on areas to try to see that are open to the public or areas to avoid that are closed to the public? _

I did almost the same thing but I took 190 through Krotz Springs and went up through Lottie and Fordoche. All the roads were open, don't figure on stopping on or near any of the structures. There will be law enforcement everywhere and sometimes State troopers with a rolling 45 MPH road block.

The Audubon bridge is very nice. Just take HWY 10 from Morganza and it will take you right to it. It is not as big as the two Baton Rouge bridges because deep draft navigation stops at Baton Rouge.

[HelmutVII]

_ Charlie,
I am by no means an expert on the Mississippi River and it changing its course. I will say that in the micro view, man has controlled the mississippi. Will man always win? There is only one person I know who has the answer to that. In the interim, the men and women of my profession will continue the good fight using scientific data and sound engineering judgement.

BigEd, Jumbo, or Helmut your thoughts? _

I think eventually the Atchafalaya will capture the Mississippi. When I don't know, next year or next century. When it does it will be labeled an ecological disaster which is basically hogwash. It's a natural event that has taken place for hundreds of thousands of years. To say that it won't happen is betting against the norm. We as humans have a short sighted view of things based on our short time frame in history. If you look at things objectively you will come to the conclusion that the only thing constant in nature is change. The Mississippi river changing its course is part of that. All you have to do is look at Google earth, Bing, NASA imagery and see all the ox bow scars, Ox bow lakes along the river to come to that conclusion.

I have drilled water wells and hit wood logs at 120 feet deep. How many floods and course changes did it take to place 120 feet of alluvial deposits at that location. Who knows, but it happened. Me picking that particular place to drill that well to find that log was pure happenstance. I still have some pieces of the chips in a jar filled with water. When I picked up the chips, I wondered when the last time that log saw the light of day. My client may have to drill another well at the same site. I'll be there looking for wood chips.

[Bandwagon King]

_ I think eventually the Atchafalaya will capture the Mississippi. When I don't know, next year or next century. When it does it will be labeled an ecological disaster which is basically hogwash. It's a natural event that has taken place for hundreds of thousands of years. To say that it won't happen is betting against the norm. We as humans have a short sighted view of things based on our short time frame in history. If you look at things objectively you will come to the conclusion that the only thing constant in nature is change. The Mississippi river changing its course is part of that. All you have to do is look at Google earth, Bing, NASA imagery and see all the ox bow scars, Ox bow lakes along the river to come to that conclusion.

I have drilled water wells and hit wood logs at 120 feet deep. How many floods and course changes did it take to place 120 feet of alluvial deposits at that location. Who knows, but it happened. Me picking that particular place to drill that well to find that log was pure happenstance. I still have some pieces of the chips in a jar filled with water. When I picked up the chips, I wondered when the last time that log saw the light of day. My client may have to drill another well at the same site. I'll be there looking for wood chips. _

Helmut, would you mind reposting the link with times & flow charts when they opened the gates on the spillway? I can't seem to find the reference you posted on. Thanks.

[Bandwagon King]

_ The designers did not have the benefit of computer modeling, CAD software and many other modern design tools that we take for granted today. The design was done by a bunch of guys wearing black pants, neck ties and white shirts with a pack of Camels in the pocket. Their tools were slide rules, and drafting was done with triangles, and parallel bars. They sharpened their pencils with sand paper. Pretty primitive but they got the job done. Also, they did not have the body of knowledge then that we have today.

They built the structure with state of the art materials for that time. Materials that are no longer used today like grade 40 Rebar and 3000 psi concrete.

The only saving grace was that if they figured 1 foot 6 inches was enough they probably made it 2 feet 0 inches. Things were heavier, thicker and wider back then. Not necessarily bad just different.

If they would build the same structure today you might see the same scheme but executed totally different. Different foundations, stronger lighter steel and rebar, higher strength concrete, wider gates.

The design is not bad, actually it's was excellent then as it is now. After all, it is almost 90 years old and has worked 24/7 since it was placed into service. _

So you're saying the ORCS is always channeling water?

[biged05]

Orcs keeps the 70-30 split. This article is a pretty good one.

http://www.americaswetlandresources....erControl.html

igeaux.mobi

[Bandwagon King]

_ Orcs keeps the 70-30 split. This article is a pretty good one.

http://www.americaswetlandresources....erControl.html

igeaux.mobi _

This has probably been asked aleady, but have they used the overbank structure? Also, wouldn't it be fair to say that now that the Atchafalaya has crested & is receding in Simmsport above the Morganza & the river is still going down in Baton Rouge that the Atchafalaya & lower Mississippi are capable of handling the flow rate & they can now start looking at closing the gates on the Morganza?

[HelmutVII]

_ Helmut, would you mind reposting the link with times & flow charts when they opened the gates on the spillway? I can't seem to find the reference you posted on. Thanks. _

I don't remember that one. Maybe somebody else did.