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14 The fine suspended sediment (<0.0625 mm) was analyzed for concentration. Each set of three bottles of supernatant was filtered through a pair of Millipore filters preweighed to the nearest ten thousandth of a gram. The dry filter pairs were placed in a Gelman filter funnel and the contents of the 250 ml supernatant bottles were poured into the funnel. A vacuum pump assisted the filtering process. The concentration of each of the three bottles was calculated by determining the weight of fines on the filter, weight of the supernatant sample, and correction factor obtained from the second filter. Additional laboratory analyses included measurement of cobble sizes captured in the Helley-Smith sampler, size distribution of bed material, photographic analysis of bed material and analysis of the sonar depth chart recordings. RESULTS AND DISCUSSION Yampa Canyon Morphology The Yampa River canyon incised meanders are the dominant physical feature in the plateau topography. This unique physical environment creates a diverse biological habitat. Complex relationships exists between the aquatic species and the habitat created by the river. Response of the physical system to changes in flow regime would disturb the stable, equilibrium conditions which support the river ecosystem. The channel morphology and aquatic environment is a function of several interrelated physical features of the system including geology, climate, basin size, topography, sediment transport and others. The following discussion will focus on the important aspects which define the range of natural conditions and processes that exist, in critical or sensitive habitat reaches of the Yampa River. The incised meanders have an average wavelength of approximately 0.62 miles. The original formative discharge for producing the paleochannel meanders with a wavelength of 0.62 miles is approximately 10,500 cfs. This is derived from empirical relationships of existing rivers (Richards, 1982). The corresponding width is about 250 feet or equal to present day width. Over geologic time the annual discharge has increased. As the river incised in bedrock, the base level dropped, increasing the drainage basin and the annual discharge. Every river system evolves in a manner that establishes approximate equilibrium between the channel and the water and sediment it conveys. The reaches in the canyon comprise a long profile shown in Figure .2 which reflects the long term evolution on geologic temporal and spacial scales. The slope-substrate-discharge relationship is complicated. Size of the bed material is proportional to the depth and slope, and generally, a milder slope will result in a smaller substrate. In the upper reaches of the canyon, downcutting is inhibited by the large substrate and the erosion resistant formation. The downstream decrease in bed material sizes is the result of sorting as a function of slope. Abrasion accounts for some of the downstream size reduction.