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~r INTRODUCTION The condition of stream channels and alluvial valleys of the Colorado Plateau has changed dramatically during the past 100 years. These geomorphic adjustments have been well studied in southern Utah, northern Arizona, and New Mexico, but are poorly known in the Uinta Basin, which is located at the northern edge of the Plateau. Geomorphic adjustments in the central and southern Colorado Plateau have affected channel planform, the distribution of channel macro-forms, the characteristics of bed substrates, and the relation between channels and their alluvial valleys. These adjustments therefore have the potential to affect the aquatic species whose life cycle depends on access to floodplains or to particular in-channel habitats. Yet, there has been essentially no research conducted which links the century-scale geomorphic history of the channels and valleys of the Colorado Plateau with the survival of the endangered endemic species of the same river systems. Geomorphic change in the central and southern Colorado Plateau has been caused by broad changes in climate that determine the frequency, magnitude, and seasonality of precipitation which in turn affects the duration and timing of runoff and sediment delivery. Land use also has the potential to change runoff regimes by direct manipulation of streams or by indirect changes in vegetation and soil structure. As a large drainage system of the Colorado Plateau, the Duchesne River has been extensively ~ _ altered and current water development proposals call for even greater future changes. The Duchesne River also comprises critical habitat for one of the endangered fish of the Colorado River basin -- the razorback sucker (Xyrauchen texanus). The most downstream 4 km of the Duchesne River have been proposed for critical habitat designation by the U.S. Fish and Wildlife Service (Maddux et al. 1993), and 6