A little bit of a twist...
In the early 1800s there was a plan to make Bayou St. John the port of New Orleans because access from the Gulf into the Lake would have been a shorter and direct line into the city.
Hind sight being 20/20... if this came into to fruition you wouldn't have needed such a monumental and encompassing levee system but maybe minor one to protect the City and the smaller communities to the south.
Then you could have built a more elaborate spillway/ dike system at Morganza where you could control flood levels flowing water either through the actual Mississippi River and through the Atchafalaya.
The encompassing levees along the entire river to Venice would not have been needed and would have allowed sentiment to move through the natural flood plains.
Even with this system there would have been erosion but probably extended the life of our present marshes(Venice to Timbalier Isles) another 100yrs or so...
ETA: The man who had the idea... James Pitot Wikipedia Link
He was President of the New Orleans Navigation Company, which was granted the right to operate a toll canal extending from Bayou St. John into the Tremé neighborhood,terminating in the 'turning basin' which eventually gave its name to Basin Street. This route saved shippers many expensive days and risks of navigating the winding Mississippi River, in the days of sail.
This post was edited on 8/30 at 8:41 am