I would wager that ALL rivers and creeks in N. America contain artifacts, its just that where the bed may be muddy, the finding them is impossible. Like was said before, you need to check out the gravel banks, and be patient. Sometimes, as in my dad's creek, the gravel bars may be exposed after a storm just to be covered up again in sand the next storm. Of course, you probably already know to turn each stone or peice of stone and remember that most of the time you may only find a small peice sticking out of the ground, just to tug it out and find a real "gloat"...or sometimes its just a broke...but then, if they were so easy to find...it wouldn't be as fun now would it?
Good luck to you. Keep us posted with your finds as we dont get to see that much from up your way.