1. In New Orleans, that would be m called a “levee breach”.
You don’t get any actual “waterfalls” until you go north to Tunica Hills, near the border with Mississippi.
And that’s not a bayou…mostly piney woods.
2. How the water got to Brer Fox’s lair was spelled out, if one bothered to actually read the “Rabbit Tales” newspaper signs in the queue.
Chick-a-Pin Hill is a wooded hill which served as home to many critters. The peak of the hill was marked by a dead-tree, which was home to the conniving Br'er Fox.
At some point, a raccoon named Rackety used the woods near Chickapin Hill for his moonshining, only for this to cause an explosion; with it being speculated that he used too many blueberries. The explosion destroyed the recently constructed dam of the Beaver Brothers, resulting in a flood which drenched Chickapin Hill and transformed it into what locals renamed as, "Splash Mountain".[2]