i kind of know the area, but regardless of knowing the area, here's what i would be concerned about:
1) You can't just go and hunt a river without asking anyone permission, unless it is a navigable waterway. If it is not, then it probably means each portion is owned by the property owner where the river runs through.
2) if it is a navigable waterway, you still need access.
3) As far as i know, you can't discharge a firearm within any city limits, so even if the above two check out, you need to make sure you are out of city limits.
another thing i've always thought about wiht trying this type of hunting, cause i've often wanted to, is the fact that if this is the case and the river is a public river, the land on either side is usually private. If i ever did this, i'd feel better about it if i talked to the adjacent landowners and let them know what i was doing in hopes to at least get their blessing.
i know this has been talked about before, anyone else have any experience on this stuff.