I’ve learned a lot about the control of flooding along the Mississippi in the last few weeks. From the dynamiting of the levee by Cairo, IL to spare the city (and the purpose of that) to the long term US Army Corps of Engineering leases along the various floodways of the Atchafalaya River, to the very name “Atchafalaya” and the distribution of the systems that control the river during flood.
Did you know that, left to its own devices, the Mississippi might actually be flowing down the Atchafalaya, skipping Baton Rouge and New Orleans?
Today, the USACE opened the first gates in the Morganza Floodway. This structure is intended to allow Mississippi river water to flow into the Levee-Protected Atchafalaya river basin and exit to the Gulf of Mexico via the Morgan City area rather than go past Baton Rouge, New Orleans, the Port of New Orleans and all the other urban/commercial/industrial concerns along the river. This reduces the peak rise of the river. It also, unfortunately, floods the crap out of the area surrounding the Atchafalaya, between the levees. USACE maps of this are available here.
These two images are the same (river) side of the Morganza floodway. You can see the water is a bit higher in the first than the second. Concentrate on the bridge beams that you can see below the fence of the floodway structure. Those are the same in both pictures.
That second picture is from this resource, which describes the measures of flood control around the lower Mississippi