When the water rises, the riffles become just more flatwater, more of a glide. Fish the edges, the current breaks. Look for underwater structure. Look around the gravel bars before splashing around in the water, because you'd be surprised how many trout feed in the shallow waters. Your predominant catch will be rainbows, stocked by the hundreds of thousands, but the river is best known for its naturally-reproducing population of brown trout.
Anglers can occasionally catch holdover and stocked cutthroats.
The river also holdscatfish, smallmouth and largemouth bass. A 6-weight won't be too heavy for some of these monsters and the high, fast water. For night fishing, 3X leaders are best. You'll want to bring along neoprene waders for the colder months, and breathables for the warmer ones. Felt soles are needed to keep from slipping on the slick rocks.