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Grams and Schmidt 5 characteristics of debris fan-created rapids and upstream pools were discussed by Kieffer (1985). Geologic structure, tributary delivery processes, and mainstem hydrology all contribute to the geomorphic character of canyon rivers. Yet comprehensive examination .of these channel-organizing elements, particularily in a system outside Grand Canyon, is lacking. Only the study of rapids by Graf (1979) addressed any of the geomorphic components of the canyons of the eastern Uinta Mountains and so the applicability of Grand Canyon models has not been tested elsewhere. 3. GEOLOGICAL SETTING AND DESCRIPTION OF STUDY REACH The Uinta Mountains are a broad east-west trending arcuate anticline, separated in the middle by a structural and topographic low. The range spans parts of northeastern Utah, southwestern Wyoming, and northwestern Colorado. The eastern Uinta Mountains range in elevation from 2,960 m at the top of Diamond Peak to 1,448 m at the Green River near the mouth of Split Mountian Canyon. Uplift and deformation of the Uinta Mountains began in latest Cretaceous time and continued into the Tertiary (Hansen, 1986). Bedrock exposures in the eastern Uinta Mountains range from highly resistant Precambrian core complexes to soft Tertiary sediments. Regionally, the rocks dip gently to the south- southwest (Hansen and others, 1983). Folds and faults cause large variations in dip over .short distances. Table 1 summarizes the rock formations, the reaches over which they outcrop at river level, and their bedrock resistance class. Bedrock resistance was adapted from the classification of Harden (1990). This semi-quantitative classification ranks bedrock on a scale of 1 to 9 in order of increasing resistance to erosion. Mapped faults in the eastern Uinta Mountains generally trend NW -SE and NE- SW (Hansen and others, 1983). Faulting occurred during the Laramide uplift and post- Laramide (middle to late Tertiary) extension. In addition to the mapped faults, Hansen and others (1983) showed an abundance of similarly trending joint sets. Nearly all of the major tributaries and many of .the smaller drainages to the Green River in the north-south