Steve it sounds like a big flathead is going to get big fish.With all the structure your talking about I would definetly have some live bluegill or shad thrown around the root systems or log jams.Make sure you cut there tail to get a blood trail.More than likely the other dominent speices of cat is going to be channels.The reason I ask about river or green worms is I used to take a night crawler and thread a couple of the green worms on with it and catch everything in the river.With channels ussally a strong scent will get there attention quick and those riverworms you'll smell on your fingers a week later.Cut shad,skip, or mooneye is a good go to bait.As far as area to fish go I like were a shallow area meets a drop, that's why I ask about the ripples.What I would probably do is anchor and give each spot 30-40 minutes if nothing move on.Drifting would be a problem with all the structure.I don't like fishing when the water is falling but everybody is going to have to deal with it.If you have steep banks make sure you throw a pole right next to the bank, I remember fishing from the bank throwing out to the middle only to find I caught most of my fish right in front of me.I haven't dedicated a lot of time to the smaller rivers in twenty somethin years but I'm sure not a lot has changed.Hope this helps and the white grapes well they could resemble some type of fish egg,of course Ive told many a friend after a good day on the river if I told all the people that ask what I caught them on I told them raw potatoes how many would show up next week with a sack a taters .LOL Good luck and let us know how you do.. Chuck