Andalusia/Quad Cities where the wing dams rule the Mississippi. Don't know what a wing dam is...it's a submerged rock or concrete wall that extends out into the channel (slightly submerged by 2 feet of water) to direct water flow. In truth it's the reason all boat manuals suggest carrying a spare prop. There are several hundreds on the upper Mississippi. This year with all the snow they may be 20 feet below the water, at least until summer. All you lake guys enjoy while I have a 108 mile fun ride from Dubuque through 4 locks to get to my marina after the river unfreezes.