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Message
re: Mississippi River Flooding - Links & Pictures in 1st Post
Posted on 5/4/11 at 11:21 pm to ScottieP
Posted on 5/4/11 at 11:21 pm to ScottieP
They are predicting the river level in Red River Landing to get to 65.5 ft so the rating give a discharge of 1.9 million.
-----------------------------------
-ScottieP
Thanks for putting up this info. I wasn't able to find out where they were getting the 1.9Mcfs number from, and from the NOAA hydrographs, the discharge disappears after the 61' stage at RRL. Here's my question for you- it seems according to the project flood that RRL was originally designed to carry only 2.1 Mcfs, and at 1.9, we're rapidly approaching that mark- i.e. the design capacity of the system. What kind of factors of safety were built into the original design- if any? In other words, if we end up getting say 2.1 Mcfs (or greater) when it crests- is everyone SOL?
-----------------------------------
-ScottieP
Thanks for putting up this info. I wasn't able to find out where they were getting the 1.9Mcfs number from, and from the NOAA hydrographs, the discharge disappears after the 61' stage at RRL. Here's my question for you- it seems according to the project flood that RRL was originally designed to carry only 2.1 Mcfs, and at 1.9, we're rapidly approaching that mark- i.e. the design capacity of the system. What kind of factors of safety were built into the original design- if any? In other words, if we end up getting say 2.1 Mcfs (or greater) when it crests- is everyone SOL?
1
Posted on 5/4/11 at 11:29 pm to NYNolaguy1
quote:
I wasn't able to find out where they were getting the 1.9Mcfs number from, and from the NOAA hydrographs, the discharge disappears after the 61' stage at RRL
I have seen that. Could very well be that they do not have measurements at that level to verify the rating so they are interpolating the flow at that stage.
Don't worry someone will be making Discharge measurements daily to verify Discharge.
quote:
What kind of factors of safety were built into the original design- if any? In other words, if we end up getting say 2.1 Mcfs (or greater) when it crests- is everyone SOL?
I do not know what they are but from what I gather their is a factor of safety in the design flood.
Posted on 5/4/11 at 11:46 pm to ScottieP
quote:
I do not know what they are but from what I gather their is a factor of safety in the design flood.
Good to know- I've always wondered about that. Hopefully we never have to guess at what it is (or isn't)
Thanks again.
Posted on 5/5/11 at 12:04 am to NYNolaguy1
LINK
The flood control plan is designed to control the "project flood." It is a flood larger than the record flood of 1927. At Cairo, the project flood is estimated at 2,360,000 cubic feet per second (cfs). The project flood is 11 percent greater than the flood of 1927 at the mouth of the Arkansas River and 29 percent greater at the latitude of Red River Landing, amounting to 3,030,000 cfs at that location, about 60 miles below Natchez.
_________________________________________________
As far as current levee construction goes, USACE's EM 1110-2-1913 addresses design and construction criteria.
There was some bitching in N.O. after Katrina that the floodwalls in urban areas only had a safety factor of 1.3, but since some of them (17th St and London Ave) collapsed still having about 4' of freeboard, the safety factor didn't really matter.
Levees outside of very populated areas can have much lower safety factors, like 1.1
The flood control plan is designed to control the "project flood." It is a flood larger than the record flood of 1927. At Cairo, the project flood is estimated at 2,360,000 cubic feet per second (cfs). The project flood is 11 percent greater than the flood of 1927 at the mouth of the Arkansas River and 29 percent greater at the latitude of Red River Landing, amounting to 3,030,000 cfs at that location, about 60 miles below Natchez.
_________________________________________________
As far as current levee construction goes, USACE's EM 1110-2-1913 addresses design and construction criteria.
There was some bitching in N.O. after Katrina that the floodwalls in urban areas only had a safety factor of 1.3, but since some of them (17th St and London Ave) collapsed still having about 4' of freeboard, the safety factor didn't really matter.
Levees outside of very populated areas can have much lower safety factors, like 1.1
Posted on 5/5/11 at 12:04 am to ScottieP
How are the levees holding from East Carroll Parish down to Tensas Parish? Is the Corp. worried about any areas around there??
Posted on 5/5/11 at 12:14 am to White Roach
quote:
I did a quick google search and all I see are stories about a levee that was intentional breached last week. Have you got more details?
i was watching WREG channel 3 when the reported said, "a levee in dyer county has failed". or something like that that.
Posted on 5/5/11 at 12:21 am to Rebel
thx
Posted on 5/5/11 at 12:33 am to White Roach
quote:
Levees outside of very populated areas can have much lower safety factors, like 1.1
I figured as much. That's what makes me nervous- considering subsidence of the existing levee material, quality of material in the levess, settlement of the soil underneath the levee, and a slew of other geotechnical issues for our levees. It's just when you look at the actual project flood the design capacity at RRL is 2.1 Mcfs. The number that was quoted in the Corps report was for that lattitude of Red River Landing, which includes water from the Atchafalaya, and the diverted water from the Miss. Thats more than just the Miss. at RRL. When they say that 1.9 Mcfs is coming down the Miss. that should ring alarm bells, because that means we're at about 90.5% of the design capacity. As you said, Katrina breached the floodwalls in New Orleans at a similar Factor of Safety (<1.0). Should that number go a lot higher, and we will be in the >1.0 FS range. I'm not insinuating that the levees will break, or that the Corps has any disinterest in the work they do- not at all. I'm merely saying that we've never put our levees and flood control structures under this much stress.
The project flood diagram I'm referring to can be found in the PDF below put out by the Mississippi River Commision on page 3.
Project Flood River Diagram on Page 3.
Posted on 5/5/11 at 12:33 am to Fireman17
Taken from the levee at Skip Bertman Dr. and River Road
MAY 2
MAY 3
MAY 4
MAY 2
MAY 3
MAY 4
Posted on 5/5/11 at 1:05 am to NYNolaguy1
Maybe the MR&T Project levees have different design standards than the Hurricane Protection levees. The river levees get beat on every Spring. I don't know...
After Katrina, all of the hurricane levees and floodwalls were inspected. In addition to rebuilding the damage areas, many other levees were raised and/or rebuilt. Out by the MRGO and in lower St Bernard Parish, they found areas that had subsided something like 2' since they were built in the late 60s/early 70s. The floodwall collapses were largely blamed on poor design (inadequate soil borings) and in some cases shoddy construction.
The Corps has received an enormous blackeye from Katrina. Many people in N.O. view them as incompetent, at best; criminally negligent, at worst. It's too bad that they all get painted with the same broad brush, because there are undoubtedly many fine people who work there. They've been busting their humps for almost five years and have spent $7.5 BILLION(!) on repairs and upgrades since Katrina. There was a segment on WWL tonight about them piledriving 24/7 to get add'l protection in place before June 1st (the start of hurricane season). Some of the neighbors were bitching about the noise!
After Katrina, all of the hurricane levees and floodwalls were inspected. In addition to rebuilding the damage areas, many other levees were raised and/or rebuilt. Out by the MRGO and in lower St Bernard Parish, they found areas that had subsided something like 2' since they were built in the late 60s/early 70s. The floodwall collapses were largely blamed on poor design (inadequate soil borings) and in some cases shoddy construction.
The Corps has received an enormous blackeye from Katrina. Many people in N.O. view them as incompetent, at best; criminally negligent, at worst. It's too bad that they all get painted with the same broad brush, because there are undoubtedly many fine people who work there. They've been busting their humps for almost five years and have spent $7.5 BILLION(!) on repairs and upgrades since Katrina. There was a segment on WWL tonight about them piledriving 24/7 to get add'l protection in place before June 1st (the start of hurricane season). Some of the neighbors were bitching about the noise!
Posted on 5/5/11 at 5:45 am to GREENHEAD22
quote:
ITS OPENING WEDNESDAY, going Friday to go get everything from our camps in the basin.
I don't see any way they open Morganza by Wednesday.
Unless some sort of failure somewhere.
Water is barely topping to potato levee this morning from what I am told. I don't think there is even any water in the forebay yet with out that it doesn't do any-good to open the damn thing.
They will open Bonne Carre long before they open Morganza.
However I think they can divert more flow to Atchafalaya via the old river structure which would also flood the basin
Posted on 5/5/11 at 7:13 am to ScottieP
ScottieP -
Thanks for your input.
Trying to help. Retired ChemE/bass fisherman here. I would like to add to your explanation. The equation cfs = average area of River at any one point (distance across x average depth at that one point as determined and calculated in square feet) x measured River velocity at that one point in ft/sec. That is, cfs at a point on the River = calculated area (sq. ft.) x velocity (ft/sec) = cubic ft./sec (cfs).
Sorry, no Cliff notes. If you really want to know how cfs levels are determined (since they influence decisions of ACOE), digest his explanations. If not, move on...........
ScottieP, your "profiler" should include a depthfinder and GPS to measure average depth x distance across the River plus a velocity meter as your boat crosses the River at that point. Could be more than this (like the Stealth helicopters in Pakistan ha ha - but, probably not). That means, cfs = a "calculated" result, not a direct measurement. The equation may be enhanced by a "Rating", but it is still calculated. Another assumption includes: any and all velocity measurements made on that river "plane" will be consistent from top to bottom of River and and from side to side of River.
Still, it's a calculation. I'm in complete agreement with you that it is a very accurate "plot" of the discharge. I just thought it is fair to let all our concerned posters know that it is still a "calculation" and not a direct measurement.
Further, let me add to your already stated "compounding" effect of rising waters. Not only does the area increase as waters rise (depth and also outwardly sloping levees that increase River distance), but also the increased water level increases the gradient and thus the velocity. Think Colorado River flowing through the Grand Canyon and the velocity increases in the rapids due to the gradient (elevation difference). I know the Mississippi is not the Colorado. Same principles apply, however.....
I really do apprecitat your contribution to this discussion so far. Keep up the good work. If I can help any please let me know.
Thanks for your input.
quote:
The estimates are quite accurate. USGS/CORPS uses a rating curve to detemine flows. It is a stage(level)/discharge(flow) relationship. As the stage increases so does the discharge.
Discharge measurements are made by driving from bank to bank via boat with a current profiler. We make measurements at different levels and plot the discharge vs level to determine a rating equation.
They are predicting the river level in Red River Landing to get to 65.5 ft so the rating give a discharge of 1.9 million.
We made a measurement yesterday morning in BR and measured 975kcfs. Take a look at the discharge for yesterday morning at our gage.
LINK
We were within the allowable error of the measurement. So our rating is accurate.
BTW this rating was developed during previous floods
Trying to help. Retired ChemE/bass fisherman here. I would like to add to your explanation. The equation cfs = average area of River at any one point (distance across x average depth at that one point as determined and calculated in square feet) x measured River velocity at that one point in ft/sec. That is, cfs at a point on the River = calculated area (sq. ft.) x velocity (ft/sec) = cubic ft./sec (cfs).
Sorry, no Cliff notes. If you really want to know how cfs levels are determined (since they influence decisions of ACOE), digest his explanations. If not, move on...........
ScottieP, your "profiler" should include a depthfinder and GPS to measure average depth x distance across the River plus a velocity meter as your boat crosses the River at that point. Could be more than this (like the Stealth helicopters in Pakistan ha ha - but, probably not). That means, cfs = a "calculated" result, not a direct measurement. The equation may be enhanced by a "Rating", but it is still calculated. Another assumption includes: any and all velocity measurements made on that river "plane" will be consistent from top to bottom of River and and from side to side of River.
Still, it's a calculation. I'm in complete agreement with you that it is a very accurate "plot" of the discharge. I just thought it is fair to let all our concerned posters know that it is still a "calculation" and not a direct measurement.
Further, let me add to your already stated "compounding" effect of rising waters. Not only does the area increase as waters rise (depth and also outwardly sloping levees that increase River distance), but also the increased water level increases the gradient and thus the velocity. Think Colorado River flowing through the Grand Canyon and the velocity increases in the rapids due to the gradient (elevation difference). I know the Mississippi is not the Colorado. Same principles apply, however.....
I really do apprecitat your contribution to this discussion so far. Keep up the good work. If I can help any please let me know.
Posted on 5/5/11 at 7:27 am to TaserTiger
Friend sent this to me. Just above Memphis I believe. Don't know the size of the tow. That is flying on the river.
Posted on 5/5/11 at 8:13 am to White Roach
quote:
The Corps has received an enormous blackeye from Katrina. Many people in N.O. view them as incompetent, at best; criminally negligent, at worst. It's too bad that they all get painted with the same broad brush, because there are undoubtedly many fine people who work there. They've been busting their humps for almost five years and have spent $7.5 BILLION(!) on repairs and upgrades since Katrina. There was a segment on WWL tonight about them piledriving 24/7 to get add'l protection in place before June 1st (the start of hurricane season). Some of the neighbors were bitching about the noise!
I think a lot of the problems with levee boards in Louisiana have to do with the way politicians have used them for years as tools to do as they please. While the COE certainly has some talented people on staff any time you take something like levee construction and maintenance which should be science/engineering based and add politics to the fray there can easily be problems. The issues of the levee boards are probably best discussed at another time on the Poli board, but it makes one wonder how this comes back into play.
Posted on 5/5/11 at 8:27 am to TigerDog83
Natchez crest has been knocked down to 62' now. that's good news. down 3 feet.
Posted on 5/5/11 at 8:29 am to mikelbr
quote:
Natchez crest has been knocked down to 62' now. that's good news. down 3 feet.
i cant say for sure, but i'm sure this is all the effects of them opening a hole in Missouri
Posted on 5/5/11 at 8:33 am to WoWyHi
quote:
That area was deserted today. I guess that stretch of the road is always lacking a human presence. Lots of cows though.
They are definitely patrolling though. I saw two levee police riding on top, and the one guy that stopped and talked to me.
Were you the guy walking the dog that looked at me funny when I drove by?
Posted on 5/5/11 at 8:33 am to mikelbr
quote:
Natchez crest has been knocked down to 62' now. that's good news. down 3 feet.
Where are you seeing this? NWS still shows 64 on their river page.
Posted on 5/5/11 at 9:01 am to PurpleGuy
May 4th around 5:30 PM
Taken across the levee from Beau Pre Townhomes/Farr Park at the rd going over the levee to the shipping company
I went two days ago (no Pics from that day) but I could see a noticeable difference just with my eyes.
Game Warden stopped my buddy who was fishing w/out a license. Asked if he caught anything? Said no. Asked for license. Nope. We can do this one of two ways: I can write you up...my buddy cut him off and said or I can pack it up. Nice warden.
Posted on 5/5/11 at 9:02 am to TigerDog83
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