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River. The erodibility factor also is important to the river slope which is relatively mild, 1.2 feet per mile, compared to the steeper reaches of the Green River in the canyon reaches upstream. The meander pattern of the shallow canyon that has been superimposed in the Uinta Formation controls the valley alignment. A secondary river meander pattern has developed on the valley floor floodplain which is confined, compressed and truncated by the canyon walls. e Canyon Geology - Canyonlands The geology of the Canyonlands reach of the Green River is a layer cake of sedimentary rocks exposed by numerous periods of plateau uplift and river downcutting. This stratigraphic collage is a series of alternating hard and soft formations forming mesas, buttes, cliffs and steep canyon walls. There are a number of facies changes (changes in rock formations within a stratigraphic interval) and nonconformities exposed in the canyon that complicate the geologic record. In this region, salt deposits that underlie the Canyonlands geology have plastically deformed and flowed, creating upwarps and anticlines. The flowage of the salt formations influenced the position of the river prior to its canyon entrenchment (Baars, 1987).. . The most prominent geological formation in the Canyonlands reach is the thick reddish- brown sandstone cliffs of the Wingate Sandstone which can be seen at the skyline. At river mile 37, the top of the White Rim Sandstone emerges at the river level and becomes the dominant formation in the study reach. Underlying the White Rim Sandstone is the Organ Rock Shale, a soft reddish-brown shale, which begins at about river mile 32. The \Vhite Rim Sandstone forms e the yertical cliffs along the river in the study reach while the Organ Rock Shale, a more erosive formation, forms the talus slopes along the river downstream of Anderson Bottom on the south bank. Channel Planform and Gradient The Ouray study reach has a mild river slope of approximately 1.2 feet per mile and a channel sinuosity of 1.7. The larger entrenched valley meander pattern has a sinuosity of approximately 1.2. The river has developed a cropped meander pattern on the valley floor. Photo 4 shows the meander pattern between the valley bluffs. The river meander pattern creates the broad floodplains on the valley floor. Downstream of the Ouray bridge, two confluences with the Green River, the Duchesne and the White, occur within about 1.5 miles of each other. The river corridors oppose each other. Historically, the presence of the White River has affected the location of the Green River on the floodplain, possibly due to its large fine sediment load. In fact, at the present time, the Duchesne River has been denied occupation of any portion of the Green River floodplain as the Green River arcs in a broad meander bend to the west. Both the Green and Duchesne Rivers have responded with sharp bends upstream of the confluence. Historic river patterns can be seen _ on all three floodplains (Photo 5). ., 13