I love the idea!
I'm an aquatic ecologist - last summer I began a study on a river I hadn't paddled yet (Deadwood R, trib to the SF Payette in Idaho, 25 mile wilderness run). For my recon trip down the river, I made a low-budget version in GIS. I combined aerial photos and other basic info (trib names, river km, landmarks, etc), printed 8 x 10" pages, laminated, punched three holes and put the pages together using key rings through the holes. While paddling I stuffed it into my kayak or pfd. It worked great for taking notes and recording UTMs with a sharpie right on the map, and I wiped the notes off with alcohol after the trip to re-use the map next time. Super useful! I would use this type of map for non-work runs, too. Probably only cost effective for popular rivers, of course. And I agree with Seadog, I'd avoid specifics about the whitewater except maybe locations of known rapids like many existing river guides do. What is considered a hazard varies so much with water level, dynamic geomorphology and wood, paddler skill, etc.
"Wheresoever you go, go with all your heart..." Confucius