An old lobe of the Mississippi River last active about 1,000 years ago, the Atchafalaya is a distributary of the Mississippi capable of handling  1.5 million cfs, or roughly half of the maximum  flow at project flood stage. It branches to the west of the main channel. Starting just north of Baton Rouge, it flows through Acadiana and reaches the Gulf of Mexico fifty miles west of the Mississippi.

The old river control structure located up river from Baton Rouge allows engineers to control the flow down the Morganza Floodway and into the Atchafalaya River.

Levees along the Atchafalaya River are damaging the ecology of the Barataria Basin and the Terrebone Basin. The Corps is acting very slowly to address those concerns even while it proposes more levees but also some coastal restoration in a massive project known as Donaldsonville to the Gulf. This project has progressed at a glacial pace since its inception in 1998. Study recommendations are due for release in September 2007. Another similar project called Morganza to the Gulf concentrates on protecting the Houma area. Authorized in 1992 this project is awaiting Congressional approval to proceed with Preliminary Engineering and Design. The pricetag is currently $886 million.

Control  of natural forces like the Mississippi River is a tricky thing requiring constant vigilance. This New Yorker article about the Old River Control Structure was first  published in 1987 and is as relevant now as it was then.