Here are a couple of photosets of the Cahaba. The first one is near the West Blocton area in Bibb county. This is the site of the famous Cahaba lilies. These photos were taken in september. The lilies bloom in may and june.
Cahaba River - a set on Flickr
These were taken below the fall line from just south of Centreville in Bibb county to the highway 22 bridge near the rivers confluence with the Alabama river in Dallas county. the river changes dramatically when it flows below the fall line.
Lower Cahaba - a set on Flickr