Much of the Chattahoochee River is within the National Park system and thus not allowed to take off, land, or operate a drone from their property so make sure if you fly the 'hooch you are in a location that is permitted to operate from the ground. Certainly you can fly over the airspace of the river parks that are within the national park system...just can't be standing on their property.
Wasn't aware of that until I looked it up. Chattahoochee River is a NRA rather than a National Park. But both administered by the park service. Not sure if that makes a difference. The maps of area do show some areas that are outside of the NRA> But I defer to the local pilots since they will know more about it.