Hey, that was my old riding ground. 1968-1973 I was at LSUBR and I rode down river on the levee 20 miles or more. There already was a road(shell/dirt/gravel) on top of the levee then; it was used for levee inspections(ha,ha) and levee board police regularily patrolled it. Once you got about 5-8 miles down river you ran into obstructions-fences, plants of various types that denied access, docks and unloading/loading facilities-and the path became just a path. You frequently had to head 1-2 miles away from the river to find the River Road when the levee became inaccessible. There are so many curves in the river that the river road doesn't actually follow the levee all the way from Big BR to NO.
Once I went to NO I rode upriver. Even in 1973 there was a good road(sometimes asphalt, other times it was shell or gravel). It extended at least 10-15 miles upriver as a decent road, and probably all the way-for levee inspections/repairs/patrols) as a car passable path.
I also lived midway between BR-NO in Gramercy,La from 1958-1970. There was a car passable path all along there also.
I'm guessing the main cost(ignoring our thieving politicians) would be to get around the various obstructions. Heck, the actual bike path(dirt sheel, gravel is already there, and there is a smooth asphalt for at least 20-30 miles of the 120 or so miles needed. Big tires bikes can easily ride the path as is; asphalt would be necessary for narrow tires, and better speeds, of course.
Thanks,
Charlie
PS I have lived within 1 mile of the river since 1958.