2011 Mississippi River Spring Floods

[Bandwagon King]

Please clue these people in on how important the river gauge data is? It is like THE determining factor for how many gates they will open or does someone just pick a number & say we'll open three then ten, then thirty more tomorrow sounds good.

The reason they use the river gauges is because no matter how smart anybody thinks they are, there are so many variables that the river gauges are the only sure way to decide when to open or shut the gates.

[CharlieK]

Almost certain flow rate has something to do with opening the flooways too....think maybe I read that somewhere.....also pretty sure no one said that the river gauge readings were unimportant. You are arguing with yourself on that one.


Of course I'm not too good at analization, so I could be wrong.

[Bandwagon King]

_ Almost certain flow rate has something to do with opening the flooways too....think maybe I read that somewhere.....also pretty sure no one said that the river gauge readings were unimportant. You are arguing with yourself on that one.


Of course I'm not too good at analization, so I could be wrong. _

The single most important overrididng factor that trumps all others is the river level at Baton Rouge & Donaldsonville. If the river level continues to remain static or fall in Baton Rouge & the river level upstream has peaked out already then where is the water going to come form that is going to cause the increase in flow rate you are projecting to come forth. As the river level upstream falls the pressure causing the flow rate to move water decreases.

If the level down stream continues to fall ahead of it, then that is proof in itself that the system as is, is working. I don't know how else to explain that one. You can't have flow rate without a source & the source is going down pretty quickly. if it doesn't hurry up somewhere in the chain, the level at Butte larose won't even make 24'. I would say this is a good thing. Wouldn't you?

[CharlieK]

_ The single most important overrididng factor that trumps all others is the river level at Baton Rouge & Donaldsonville. If the river level continues to remain static or fall in Baton Rouge & the river level upstream has peaked out already then where is the water going to come form that is going to cause the increase in flow rate you are projecting to come forth. As the river level upstream falls the pressure causing the flow rate to move water decreases.

If the level down stream continues to fall ahead of it, then that is proof in itself that the system as is, is working. I don't know how else to explain that one. You can't have flow rate without a source & the source is going down pretty quickly. if it doesn't hurry up somewhere in the chain, the level at Butte larose won't even make 24'. I would say this is a good thing. Wouldn't you? _

I DID NOT predict anything about the flow rates of the river, I ASKED if anyone knew what the current flow rates THROUGH the control structures at old river were. As the Atchafalaya river has dug a deeper channel and the Missississippi river has risen since the original design of the structures, the height distance between the two has grown. This increases the head and would tend to lead to greater flow rates and velocities through the structure for the same relative river stage as 20,30 or more years ago. That velocity and high flow (turbulent, violent flow) is what can scour and undermine the structures leading theoretically to a failure resulting in the river shifting channels. If this happens we have a whole different problem.

The system seems to be working fine now, and as long as those structures hold all will be ok (unless your house is in between the levees). IF the structures fail, though.......

[jumboragncajun]

_, I ASKED if anyone knew what the current flow rates THROUGH the control structures at old river were.

660,000 cfs

[CharlieK]

_ 660,000 cfs _

Is that through the control strucutures (low sill and aux.) or through morganza?

Also where can you find the information online?

[CajunRed]

Man...this is getting interesting. :-)



igeaux.mobi

[CajunRed]

Sometimes I don't fully understand some of the info you engineer types are posting, but I thank y'all just the same for taking the time to share your knowledge with us. We are all going thru something not seen in almost 50 years...and, hopefully, won't see again in our lifetimes. I appreciate the chance to study it as it happens.

Thanks, guys!

Red

Look Commander Eads, I know the damn river stages are important, everybody does. I also DID NOT predict anything about the flow rates of the river, I ASKED if anyone knew what the current flow rates THROUGH the control structures at old river were. As the Atchafalaya river has dug a deeper channel and the Missississippi river has risen since the original design of the structures, the height distance between the two has grown. This increases the head and would tend to lead to greater velocities through the structure for the same relative river stage as 20,30 or more years ago. That velocity and the subsequent flow (turbulent, violent flow) is what can scour and undermine the structures leading theoretically to a failure resulting in the river shifting channels. If this happens we have a whole different problem.

The system seems to be working fine now, and as long as those structures hold all will be ok (unless your house is in between the levees). IF the structures fail, though.......

igeaux.mobi

[HelmutVII]

_ Is there anywhere that the corps is posting what flow rate the control structures (low sill and aux.) are flowing? Curious to see how they compare with the design flow rates. I know during 73 the low sill flowed at a higher rate than expected due to the increased head difference between the two rivers since the structures were designed. _

I think ORCS is pretty much maxed out. Since 1973 they have constructed the Auxiliary Structure which increases the flow rate through the ORCS complex. Anything below Baton Rouge should be labeled as "Crested" or "Cresting" because the combination of Morganza and ORCS should take enough water out of the Mississippi River to cause it not to go any higher. (this is as planned). I don't know whether there is anything in the RAS model versus current conditions that would cause the current predicted river stages to fluctuate up or down. I just heard that they are still predicting 27.0 at Butte La Rose sometimes in the next week or two. They are predicting the water to remain high for about 6 to 8 weeks. Whether that holds true or not remains to be seen.

One of the things you have to remember is that the areas flooded upstream all the way to Illinois are not yet completely drained. They will not completely drain until the current plug of high water being handled by the basin and the lower Mississippi has passed. Once this happens there should be little or no adverse slope in the water surface or the hydraulic grade line all the way to the Gulf of Mexico. In other words, both the water surface AND the Hydraulic Grade Line will indeed be sloping down to the Gulf of Mexico. That fellas is a good thing but that isn't happening yet.

[jumboragncajun]

When you have gone & studied all the charts & understand that the river has already peaked at Natchez today

"peaked at Natchez today" you say? That alone should tell you something.
i.e. if the peak flow is at Natchez today, it's not in Baton Rouge yet.

I don't need to 'study charts'. Flow in/flow out.....DETERMINE what those elevations are that you are such a fan of. Nobody said gauge levels were not important. You are talking elevations, and elevations alone. I am saying there is more than just that. I am speaking in VOLUMES. Volume is volume no matter what, where, when...it is still a volume. Elevation is dependent on MANY MANY things....area, depth, velocity, wind, tide, elevation of the surrounding area. The discharge DETERMINES the gauge elevations. A large volume of water is still coming down the river.

& that the river at Knox landing just 15 miles to the south is going down in level as well as the Red River Landing & Baton Rouge

2 more bays were opened yesterday.

without Morgan City or Butte Larose going up aprreciably then you don't understand that the Calumet Cut & the river at Morgan City are more than capable of handling the excess overflow of the existing structures as they now stand & they won't have to open any more gates to contain this thing at present & lower levels.

You have a fundamental misunderstanding of the entire process. The basin is a storage container. It does not matter if it handles what they are putting in, it is serving it's purpose well and as long as the flow in is larger than the flow out, it will rise. That DOES NOT determine if they need to open more gates. The capacity of the mississippi river will determine if more gates need to open.

I am not the one running the thing, I am just giving an honest analization that at the present can't be argued against without having better data. Come back when you have better data than the river levels. Obviously this is the most important piece of information the Corps uses or they wouldn't spend so much time collecting it. _

River levels are what people understand. People know the elevation of their house, the top of the levee, how deep so they can put their boat in the basin...etc... What determines those levels are the discharges. If I tell someone in Natchez that 2.7mcfs is passing thru the river, they want to know what that means to them, or how that effects them...ie. level.. It is also the easiest thing to measure. But the control structures are designed and controlled based on volumes. If I ask you to read me the level of a full 5-gallon bucket, you might say to 2 feet. But if you throw that 5 gallons into cypress lake, the level of cypress lake will not change, but the volume did.

[CharlieK]

_ Sometimes I don't fully understand some of the info you engineer types are posting, but I thank y'all just the same for taking the time to share your knowledge with us. We are all going thru something not seen in almost 50 years...and, hopefully, won't see again in our lifetimes. I appreciate the chance to study it as it happens.

Thanks, guys!

Red

igeaux.mobi _

Some of these are listed elsewhere in this thread, but good reading:

"The Control of Nature" McPhee
"Rising Tide" Barry
"Crevasse: The 1927 Flood In Acadiana" Conrad and Brasseaux
"If the Old River Control Structure Fails?" Bulletin 12 Louisiana Water Resources Institute - Kazmann and Johnson

[HelmutVII]

There is nothing that Jumbo said that is in error. I would not argue with him.