The barge was trying to fix a bridge or overpass.Your aunt is nuts, she fed you a line, or you heard wrong.My Aunt saw it happen, then was rescued from her roof.
These 'canals' are NOT, repeat NOT used for any sort of comercial traffic or boats or ships, THEY ARE USED AS PART OF THE PUMPED DRAINAGE SYSTEM IN NEW ORLEANS.
You seem to know about the canals.
Do they have locks on the end to limit flooding in case of a break? And why such a big profile if just for drainage?
I would think that something on the order of 6' dia. would be sufficient given the size of the pumps.