2011 Mississippi River Spring Floods

[biged05]

Ok guys.I've been busy riding all day and this is a lot if info to process on a cell phone as I wait to see if our col. Is coming in my area.

Jumbo,
Not sure where you got 660,000 from but you're close as of the readings this morning Not sure if it's available to the public so I'll just say it's less than that but the max so far that I know of In this event was almost there.

King,

As much as stages make sense the determination of gate openings is almost 100% on flow in cfs. Sometimes I'd wish they would go a little more on stage readings, but when they talk about trigger points it's all about cfs.

igeaux.mobi

[jumboragncajun]

_ 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. _

One more thing. Between the Wax and Atchafalaya outlets, 632,000 cfs is currently being discharged out of the basin.

Coming into the basin is 660k at Old River, 114k at Morganza, 11k from Red River. That is more than what is being discharged. If we assume no more bays are opened, the old river is at max flow, the Red River alone is projected to dump 350k into the basin. That is 492,000 MORE cfs going into basin than what is dumping out of it. To put that in perspective, that is nearly 221 MILLION gallons EVERY MINUTE going in the basin to be stored.

[NewsCopy]

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The rest of the story

[HelmutVII]

_ As much as stages make sense the determination of gate openings is almost 100% on flow in cfs. Sometimes I'd wish they would go a little more on stage readings, but when they talk about trigger points it's all about cfs.

igeaux.mobi _

I think that's because the original congressional act referenced flow rates and percentages of the flow rate that is split between the Atchafalaya and Mississippi. I could be wrong though. If that is the case and IF they do it any other way YOU KNOW somebody is going to catch them on it and there will be hell to pay.

It could be a good thing too. Given that hydrologic and hydraulic conditions could vary over time, you could have a different flow rate at the same stage at a given point. It certainly is a model that not only is complex but varies.

[LsuULfan]

_ I think that's because the original congressional act referenced flow rates and percentages of the flow rate that is split between the Atchafalaya and Mississippi. I could be wrong though. If that is the case and IF they do it any other way YOU KNOW somebody is going to catch them on it and there will be hell to pay.

It could be a good thing too. Given that hydrologic and hydraulic conditions could vary over time, you could have a different flow rate at the same stage at a given point. It certainly is a model that not only is complex but varies. _

Seems to be based upon the Project Design Flood

http://en.wikipedia.org/wiki/Project_design_flood

[CajunRed]

That was a helluva chart to the right. I got a little nauseated just looking at it.


igeaux.mobi

[sportsfanatic21]

Is there a RaginPagin dictionary so I can figure out what the hell y'all are talking about?!!!

Seriously, this is the most educational outlet I've seen regarding this situation. Thanks to all that are contributing, and keep it rolling!!!

igeaux.mobi

[HelmutVII]

_ Seems to be based upon the Project Design Flood

http://en.wikipedia.org/wiki/Project_design_flood _

You are correct but they define what a "project design flood" is by flow rate and not stage. And I think that was established in the original 1928 act. I could be wrong though.

However, all of the spliways and flood gates are rated in flow rate. One of the things that defines rate of flow is "Delta H" (difference in head) which can be measured as "Delta stage" (difference in stage). (trying to explain without being too technical. After doing this for over thirty years it's like knowing 2 + 2 is four)

[LsuULfan]

_ You are correct but they define what a "project design flood" is by flow rate and not stage. And I think that was established in the original 1928 act. I could be wrong though.

However, all of the spliways and flood gates are rated in flow rate. One of the things that defines rate of flow is "Delta H" (difference in head) which can be measured as "Delta stage" (difference in stage). (trying to explain without being too technical. After doing this for over thirty years it's like knowing 2 + 2 is four) _

Have not read it yet-but the Wiki footnotes an information paper from the MRC which seems to explain how they came up with the project design flood over the years

http://www.mvd.usace.army.mil/mrc/mr.fo%20paper.pdf

[CharlieK]

The problem for the control structures is they won't flow only what they were designed for. They will flow what they will flow based upon the head (elevation difference) between the two rivers along with other factors. Now if the structures are designed to move 620,000 cfs of water, but the head and flow rate of the rivers forces more than that through the structure there is nothing to stop the water. If this happens they are exceeding the design rating of the structure and it could be damaged. I think this actually happened during the 73 flood. Even though the river was no where near the Project Flood flow rate in 73, the increased head between the two rivers (due to the natural deeping of the Atchafalya channel and rise of the Mississippi) caused the flow through the low sill to exceed the capabilites of the structure. Morganza was opened to relieve this pressure (reduce the head) and the structure survivedbarely. It was badly undermined, lost one of the inlet retaining walls, etc. This is why the aux. structure was built.

I'm not saying this IS happening, I'm asking how close we are. There are two issues here one is flooding Baton Rouge, New Orleans, etc., the other is stopping the river from changing course into the Atchafalaya. Honestly the second scares me far more than the first, as it would change life as we know it in Louisiana, and would be a terrible blow to the economy of the country at a time we can ill afford it.

[NewsCopy]

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The rest of the story

[Bandwagon King]

_ That is your standard line when someone dares to disagree you.


"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 thingsarea, 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.


2 more bays were opened yesterday.

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.


River levels are what people understand. _

Levels are confirmation factors of these volumes the brainiacs are so in love with If the level is lower & the crest is sooner, obviously either the flow rates volumes used were inacurate, because the flow rate to handle the total volume was higher than calculated or the volume to evacuate was less than expected. That is why levels are the final trump card in determining how many bays are open to the floodway.

In this case I believe both were the case. That & the fact man misdiagnosed mother nature's ability to take a drink. A single water oak can drink up to 500 gallons of water a day. Multiply that by milllions & millions of thirsty trees & that is an incalculable amount of volume.

As for the case of not needing to study flow charts, I'm pretty sure that's what the Co. man, Tool pusher, & Engineer on the Macondo well said about two hours before the greatest man made disaster in the history of America.

[Bandwagon King]

_ The problem for the control structures is they won't flow only what they were designed for. They will flow what they will flow based upon the head (elevation difference) between the two rivers along with other factors. Now if the structures are designed to move 620,000 cfs of water, but the head and flow rate of the rivers forces more than that through the structure there is nothing to stop the water. If this happens they are exceeding the design rating of the structure and it could be damaged. I think this actually happened during the 73 flood. Even though the river was no where near the Project Flood flow rate in 73, the increased head between the two rivers (due to the natural deeping of the Atchafalya channel and rise of the Mississippi) caused the flow through the low sill to exceed the capabilites of the structure. Morganza was opened to relieve this pressure (reduce the head) and the structure survivedbarely. It was badly undermined, lost one of the inlet retaining walls, etc. This is why the aux. structure was built.

I'm not saying this IS happening, I'm asking how close we are. There are two issues here one is flooding Baton Rouge, New Orleans, etc., the other is stopping the river from changing course into the Atchafalaya. Honestly the second scares me far more than the first, as it would change life as we know it in Louisiana, and would be a terrible blow to the economy of the country at a time we can ill afford it. _

I understand your worries & I would like to more about that occuurence myself. It certainly appears that the worst is over. The lower Atchafalaya is handling everything the upper Atchafalaya is throwing at it & that's a good thing. The Mississippi goes below flood stage on or before May 30th in several places according to the weather channel.That was the original expected crest date. If the flooding is going to happen it will have to happen between now & then.

[Bandwagon King]

_ Ok guys.I've been busy riding all day and this is a lot if info to process on a cell phone as I wait to see if our col. Is coming in my area.

Jumbo,
Not sure where you got 660,000 from but you're close as of the readings this morning Not sure if it's available to the public so I'll just say it's less than that but the max so far that I know of In this event was almost there.

King,

As much as stages make sense the determination of gate openings is almost 100% on flow in cfs. Sometimes I'd wish they would go a little more on stage readings, but when they talk about trigger points it's all about cfs.

igeaux.mobi _

Don't levels determine the basis for calculating flow rates to begin with. Not being a math major or engineer, it would seem to me that determining the CSF of a river would be done by calculating the the height by the width by the length of the discharge. I also don't get how a hydrostatic head can be put in there to determine pressure without levels. The bottom line to a lot of people is if the river goes up you open the gates. If it goes down, they should swing the other way. I don't suppose I have to tell you the conspiracy rumors are already starting to boil. It would be a real shame to see gates flying open when the Mississippi is already turning the other way.

[HelmutVII]

_ Have not read it yet-but the Wiki footnotes an information paper from the MRC which seems to explain how they came up with the project design flood over the years

http://www.mvd.usace.army.mil/mrc/mr.fo%20paper.pdf _

The paper does indeed give a brief synopsis of how they came upon the different flow rates to determine what a project design flood is at various stations of the River. However, they still define a Project Design Flood in CFS and not stage.

What one needs to remember is that any given stage at a SINGLE point along a river DOES NOT define what the flow rate is. What defines the flow rate is the DIFFERENCE in stage between two or more stations of a river AND the distance between those stations. It has everything to do with the slope of the hydraulic grade line and the cross sectional area of the channel (that is the cross sectional area of the channel until it gets to areas affected by tides).

It is entirely possible to have a stage of lets say 50.0 at a given point in a river and have, lets say 150,000 cfs flow rate during one event and then have a stage of say 50.5 at the same point and still have the same flow rate of 150,000 cfs. The flow rate at any given point is ENTIRELY dependent on the relative stage of the points upstream AND downstream.

The TOP of the water is literally falling down the river and how fast it falls depends on the relative difference in the top of the water from one point to another. (it's hard to explain the concept because common sense asks how can something fall when it's on the ground).

It took me a long time to fully comprehend this concept, but once I did, it made perfect sense. To this day, I will stand on a drainage structure (especially one that I designed) and just watch the water (even in the rain). Really satisfying to watch it work as designed. It also helps me to understand the nature of the beast.