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Response of the Yampa River channel to streamflow and sediment supply scenarios that lead to a sediment budget surplus or deficit may be described in general terms at best. When the amount of sediment transported is greater than the sediment supply, channel degradation will occur and will continue until stream gradient is decreased or the bed is armoured with material too large to be transported. In OeerlOdge Park the Yampa River has an alluvial channel, but bed probing at low flow and observations of scour at high flow indicated the presence of coarse-grained material and local bedrock several feet below the sandy bed material. A deficiency of alluvial sediment in the Deerlodge Park reach probably would result in channel degradation over a period of years to this coarse material or bedrock. The amount of degrada- tion, the degree to which slope could increase and the time involved are difficult to predict for the entire reach, but scour at the Oeerlodge Park gage site probably would be, at most, on the order of 10 ft below the present low-flow bed profile (fig. 4). Reduced streamflow and(or) scour accompanying a sediment budget deficit in Oeerlodge Park would change the stage-discharge relationship there. Flood flows of a given discharge would inundate banks to a lower level and encourage the estab 1 i shment of ri pari an vegetation on banks and bars that are now intermittently flooded and scoured. Flourishing vegetation would result in sediment deposition on banks and bars and cause the river channel to narrow and deepen. ' Streamflow and supply scenarios that result in a sediment budget surplus would have different effects on the channel in Deerlodge Park. Sediment would be depos i ted in the channe 1, ra is i ng the bed e 1 evat i on and i ncreas i ng the frequency with which floods inundate the flood plain. Some sediments carried at higher flows may be added to the flood plain by overbank deposition. Often the slope of an aggrading river reach increases; this is possible in Deerlodge Park.,' Schumm (1977, p. 133) notes several different channel adjustments that can occur if streamflow is reduced and sediment load is increased or remains constant, including an increase or decrease in channel width, an increase in the width to depth ratio, reduced sinuosity, and increased slope. A channel eventually will achieve a new equilibrium, but complete adjustment will require a long period of time. Channel instability can be anticipated until equilibrium is attained. The river channel in the Yampa Canyon also will be affected by long-term changes in streamflow regime or sediment supply. If the timing or magnitude of peak discharges are significantly altered, sand deposited on banks and bars from 1 ate summer through wi nter may not be swept away seasonally. These formerly transient features, largely composed of sand, could become more 'permanent during periods of flow regulation through armoring or the growth of vegetation. A channel restricted by resistant banks will have a reduced capacity to transmit short-duration, high-volume streamflows, thereby increas. i ng the potential for fl oodi ng of 1 owl and areas (Taylor. 1978). Ke 11 erha 1 s and Gill (1973) reported that regulation of main-stem rivers in northel'n Canada upset the phase of di scharge regime with respect to tri butary flow. Floods on tributaries of l'egulated Canadian streams wel'e more likely to occur when the river stage at the confluence was considerably lower than normal. In the Vampa Canyon, a similar situation could permit bars to build near tributary confl uences over a peri od of years. These features, 1 i ke resi dua 1 29