Click on the map for the larger view.
The map above shows the locations of the Old River Control Structure and the Morganza Floodway.
Above is an aerial view of the Old River Control Structure. Image from Wikipedia.
Shown above is the Morganza Floodway with one bay open. As of now, 11 bays are open. The US Corps of Engineers expects to open 31 of the 125 bays in the floodway.
In the comments to this post at Wounded Bird, Paul (A.) asks a question and references an article in the New Yorker by John McPhee, written in 1987:
Is the opening of the floodway to the Atchafalaya the beginning of the end for Baton Rouge and New Orleans?
In response, I wrote a long comment which I decided to edit and use in a post.
Paul (A.), I read the article by McPhee when it came out in 1987. He writes about the Old River Control Structure at Simmesport, north of the Morganza Floodway. The Mississippi River wants to take the most direct route to the Gulf of Mexico, which is through the Atchafalaya River basin. If that happened vast areas would be flooded, and the Baton Rouge and New Orleans ports would be finished as major ports. The passage of large ships between NO and north of BR would cease, because the Mississippi River would not have enough water to support major shipping.
The Old River Control Structure was built to direct the major flow to the Mississippi River rather than the Atchafalaya River at roughly 70%/30%. McPhee and others think that the structure could fail and the river eventually have its way, and they may be right. However, since the article was written, an additional structure was added to the ORCS complex, which serves as further reinforcement to prevent a failure. We shall see.
The purpose of the Morganza Floodway is entirely different. It's built to send water into the Atchafalaya River basin to protect Baton Rouge, New Orleans, and the refineries and chemical plants along the Mississippi between Baton Rouge and New Orleans in the event the Mississippi reaches flood stage, which it has now. The flooding of the Atchafalaya River basin is to lower the level of water in the Mississippi River to prevent overtopping of the levees and to reduce the intense pressure from the high waters in the river, to prevent breaches. Either event could have catastrophic consequences.
I hope this helps.
Posted with the caveat that I am neither a flood engineer nor an expert on flooding.
