An addendum on opening the Morganza Spillway (tmi3rd)

I know I'm breaking the blog rules by reading the blog before posting, but I just wanted to throw an extra knowledge log on the fire about what we're seeing down in Louisiana. A quick shout-out to 1LT J.T. Gabler, LA National Guard/ Army Corps of Engineers for his technical assistance in writing this- during the oil spill, he was the commanding officer on-scene in Plaquemines Parish, and you probably saw him interviewed during the TV time... he got a lot of air time in that time period.

Anyway, this is the first time Morganza has been opened since 1973. The Mississippi River, if not diverted, is predicted to get within about six inches of the tops of the levees in New Orleans and Baton Rouge, which causes all sorts of unpleasantries ranging from putting a lot of pressure on the levees to preventing shipping traffic from transit (ships can't get under bridges, power lines, cross-river pipelines, etc.) to the potential flooding of seven of the nation's gasoline refineries.

The Morganza Spillway is located roughly 40 miles northwest of Baton Rouge, at river mile 280. The official flow of water necessary to consider opening it is 1,500,000 cubic feet per second. Water will not flow into the spillway if open unless the river is well above flood stage.

Below the fold, a graphic and some more information...

Graphic from www.nola.com.

As you can see in the graphic above, there is a smaller spillway down at the southwest side of Lake Ponchartrain called the Bonnet Carre spillway- it allows the river to flow into the lake at a rate of 250,000 cubic feet per second. It is open as of this writing.

The Corps of Engineers is opening the spillway to 25%, allowing 150,000 cubic feet of water per second to flow into the Atchafalaya River Basin, flowing down to the Atchafalaya Swamp and Bay. The two big population centers affected by this are Morgan City and Houma, which are both significant port cities that handle shipping, fishing, and petroleum. Part of the run-up to this has been the significant presence in the news of the impending release- this is part of protocol to give residents in the area ample warning that an opening is coming and to prepare.

As mentioned in the article Drew linked to at www.nola.com (that's the Times-Picayune website, the newspaper in New Orleans), a swath 20 miles wide by 150 miles long will be flooded, affecting about 25,000 people and 11,000 structures. The big impacts will be on fishing, agriculture, petroleum, and shipping... there are cattle down there, as well as sugar cane, oil and gas production, and the usual port facilities. Also, the Atchafalaya Swamp- a key wetland for hurricane protection- will get a lot of water into it.

At the Wikipedia page on Morganza, there are graphics indicating the flooding scenarios predicted by the Corps of Engineers. By opening the spillway, the intention is to lower the amount of water travelling past Baton Rouge and New Orleans, as well as protect the seven oil refineries, assorted petrochemical plants, and nuclear power plant, from flood damage.

So that's some background... obviously, this is pretty historic flooding. This is, according to Mrs. tmi3rd (a meteorologist for the National Weather Service), a result of the days and days of continuous rain across the middle of the country. The stuff you've seen about flooding near Cairo, IL (requiring the levee to be blown up across the river on the Missouri side) and at Memphis makes its way down to the mouth of the river, and it's made a hell of a mess for everyone in its path.

Here's a link to video of the spillway opening.

posted by Open Blogger at 05:39 PM

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