The upper DH area much smaller than the lower. Much tighter also.
It has a long slow deep-water stretch in its upper reaches that begins behind a Boy Scout Camp. The lower part is opposite; more classic mountain freestone with shallow pockets, runs and riffles punctuated by an occasional pool. Fish are usually well spread out early in the season, but definitely conglomerate later, tending toward cooler and more oxygenated water. The Upper DH area stays cooler longer and the fish generally hold over better. But it is more difficult to fish, imo.