2011 Mississippi River Spring Floods

[Cajunbander]

So, where would be a good place to take pictures of the high water in the Atchafalaya (I'm amazed I spelled that right) Basin? I'm not familiar with that side of Lafayette, I'm more familiar with Lafayette going west.

[CajunRed]

They are talking about levels that are FIFTEEN feet above what you are seeing here, so this is not even close to representing what we will see about two weeks from now.

These are pictures I took at the Bayou Benoit Landing from the top of the levee. First picture is Sunday (low tide) and the next two are Wednesday (high tide). If we get the amount of water projected, it might reach the top but probably won't. I saw government trucks (USGS) parked out there today, which is never a good sign. At least they parks on the other side of the levee so the fisherman could park at the landing.

igeaux.mobi

[HelmutVII]

_ If the river rises in Berwick until the hydraulic force up river causes it to flow hard enough to push that water out, it causes Bayou Shane to back flow into Amelia & even up to Stephensville, thereby exasterbating an already dangerous situation.

To start answering one of your questions this morning about the river coming up at Berwick and Morgan City already. The Old river Control structure is operated in such a way to divert 30% of the flow of the Mississippi water into the Atchafalaya river until the flow in the Mississippi River at the Red river landing reaches 1.5 million cfs. (After that the flow is split 50/50). Normally lets say the flow at that point is say 800,000 cfs (just to pick a number) 30% of that is 240,000 to the basin and then to Morgan City. 30% of 1.5 million is 450,000 cfs in the basin almost double 240,000. So right now there is about 450,000 cfs of water to Morgan City without Morganza opening. So the Morganza spillway does not need to be open for the water level to rise at Morgan City.

Secondly, When you get into river delta regions (like below Morgan City) the depth of the channel makes very little difference in the conveyance of water at higher levels. For example, if there would be no flood now, and they decided to go out and dredge the existing channel to a depth of one mile deep, how would that affect the water level of the channel. The answer is no affect at all, why, because every scoop of soil taken out of the bottom of the channel would be replaced by water coming in from the Gulf of Mexico. The only thing you would have been successful in doing is facilitating salt water intrusion. In flow conditions where there is a constant supply of water and the land slope is not great (rivers in Louisiana), the only way to significantly increase conveyance is to make the river wider at the water surface. (sounds like a flood to me).

I have to generate some maps and take some photos to TRY to more fully explain physically what is going on south of Morgan City but I have to go to work. If you have time today get on Bing or Google earth, travel up the west levee from Morgan City and try to find the Wax Lake outlet and the Charenton flood gates on the levee. Follow the Wax Lake outlet to the Gulf and you will see an almost perfect river delta. (About the same thing is happening at the Charenton outlet). Think about what is happening at that delta and try to relate that to what is happening at the confluence of the Atchafalaya and Bayou Shane.

[Big Buds]

Is there any possibility of the flood waters cresting I-10?

[awadelewis]

_ Is there any possibility of the flood waters cresting I-10? _

Current worst-case projections say it won't with the crest being about 4 to 6 feet below the level of the Basin Bridge.

[Big Buds]

_ Current worst-case projections say it won't with the crest being about 4 to 6 feet below the level of the Basin Bridge. _

Does that change the structural integrity of the bridge? Having that much water flowing beneath it.

[Chop]

What would happen in a worst case if they opened the Morganza and had mechanical problems and could not close it?

[MetryCajun]

_ What would happen in a worst case if they opened the Morganza and had mechanical problems and could not close it? _

I do not think that would be a problem. These are not automated gates. They are manually pulled up by a crane. Also, the river will receed at some point this summer where water would not flow through the gates even if they were left opened.

[MetryCajun]

Here is a good reference story on the Mississippi River and the River Control Structure.

http://americaswetlandresources.com/...erControl.html

[biged05]

Helmut,

Could you go down to Morgan City and explain the dredging part you posted to them?! Maybe they'll listen to you!

Chop,

The gates are lifted with cranes on the structure. If they would break down there are extra parts, and if there is still a problem they could be placed back with a mobile crane. The gates themselves slide into slots and have rollers on them.

igeaux.mobi

[cjr3888]

Red,
I understand the max of 15 feet, but what you can't see is that there is another body of water behind me. From my house, water naturally flows towards the basin so Fausse Point would have to back up before the flood reaches my area. If the water reaches me, then there will be alot more people underwater. I'll keep posting pics to show the level once it starts rising.


igeaux.mobi

[CajunRed]

Sorry.

Red,
I understand the max of 15 feet, but what you can't see is that there is another body of water behind me. From my house, water naturally flows towards the basin so Fausse Point would have to back up before the flood reaches my area. If the water reaches me, then there will be alot more people underwater. I'll keep posting pics to show the level once it starts rising.


igeaux.mobi

igeaux.mobi