Lava Falls Trail is a 3 mile out and back trail located near Colorado City, AZ that features a waterfall and is only recommended for very experienced adventurers. The trail is primarily used for hiking and is accessible from September until May.
The description of this trail is misleading. There are large rapids at the bottom but I wouldn't call it a waterfall.
The trail is grueling and hard to find at times, but it was fun to go to the bottom of the Grand Canyon and back in less than a day.