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Atachafalaya after Morganza Opening: Where the water goes; when does it get there.

The Corps of Engineers has released maps that show where the floodwater released through the Morganza Spillway will goes, how long it will take to get there, and how deep it is expected to get. It will over time cover all of the Atchafalaya Basin between the guide levees and all of the Terrebonne Basin to the Bayou Lafourche ridge. The maps can be found here. If you need to review the structure of the floodway, go here.

The first 48 hours

In the first 48 hours water will fill the Morganza Floodway and the eastern half of the Atchafalaya Floodway between the East Protection Levee and the eastern Atachafalaya River Levee, which ends a little north of I-10. Within 30 hours it will come to the end of the western Atchafalaya River Levee and start filling the Atchafalaya Floodway between the river levee and the West Protection Levee. The water will move north through that portion of the floodway.

The first 48 hours, Part 2

That water backing up outside the floodway at 144 hours and 192 hours comes from water spreading out through the western Terrebonne Basin south of the floodway.

At 72 hours in the Atchafalaya Basin

At 72 hours the water will have filled the floodway, reached Morgan City, and begun streaming into Atchafalaya Bay along the Lower Atchafalaya River and the Wax Lake outlet. The Gulf Intracoastal Waterway crosses the Lower Atchafalaya, picks up water streaming out of the floodway, and carries east to the Vermillion Basin and west to the Terrebonne Basin at 84 hours, reaching the Bayou Lafourche ridge at 192 hours.

At 96 hours water begins to bleed into the Terrebonne Basin

The Corps has also estimated how deep the water will get at each point along the way. Maps found at AskLouise.gov.

Scenario #1, Bonnet Carre fully open, the Morganza at 50% capacity

Scenario #2: Morganza closed, Bonnet Carre fully open

Scenario #3: Morganza closed, Excess water through Old River, Bonnet Carre fully open


5 Responses

  1. So, I spent all afternoon getting stuff off the ground in the shed up at Camp Dularge. Tomorrow, taking care of more stuff just in case we get some water here.

    • Bayou Woman:

      You all get it from the Gulf; now you get it from the river.

      I will check on Paul Kemp and the 20-80 split.


  2. Good luck they are saying no 50% open but 25% open at peak so that might help some people.

  3. I’ve been quite intrigued by articles such as this one, which point to wetland development, etc., all along the Mississippi as a way to help mitigate future disasters.

    I’m curious about your view of this. Reasonable? (I suspect it’s time to move on to your book, now!)

    Of course there always are the politics and such, but I’m one of those who has thought of wetlands only in terms of, say, south LA. Clearly that’s an inadequate view of things.

    While there’s a Mississippi River Commission, I think a whole lot of people think of the river only in terms of their “chunk” of it and pay little attention until it starts getting dramatic in Memphis, Vicksburg, NOLA, etc. A larger view – in every sense – has to come, and this may be a good time for that to happen.

    • In 1993, the states that had lost the most wetlands, both in the uplands and in the floodplain, experienced the worse flooding.

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