I'm not sure. But there is a band of higher ground between the two rivers and a band of lower ground suitable for a canal running close to the existing Mississippi channel from the low ground along the Atchafalaya. That IMO is the logical place to build - because it's close enough to surviving NOLA infrastructure to where workers in the new town could commute to it but close enough to a possible Atchafalaya canal that the town would become the primary port once the canal was complete.
what? are you wanting to rebuild near Breaux Bridge????
Boudreaux and Thibodeaux might get upset with all the jigs coming that way...