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<br />banks and poi nt bars, woul d become co 1 oni zed by vegetati on above the flood <br />level of the new flow regime. <br /> <br />Reductions in annual sediment supply to the Vampa Canyon also will affect <br />the river channel to some degree. In the Vampa Canyon, extensive net degrada- <br />tion of long reaches of the channel that often accompanies a sediment budget <br />deficit probably will not occur because the channel flows on bedrock, talus, <br />and coarse debris from tributaries. If the sediment load is drastically <br />reduced, local ero$ion of sand from some beaches, bars, and pools may occur, <br />as it has in places on the Colorado River below Glen Canyon Dam (Howard and <br />Dolan, 1981). <br /> <br />The nature of changes in the river channel of the Vampa Canyon that would <br />accompany a long-term surplus in the sediment budget' are more difficult to <br />ascertain. The sediment supply to Yampa Canyon is equal to sediment transport <br />through Deerlodge Park. Average channel slope through the Vampa Canyon is <br />much greater than channel slope through Deerlodge Park; therefore, all sedi- <br />ment supp 1 i ed from Deer lodge Park shoul d be transported through the Vampa <br />Canyon on a long-term basis. However, on a year-to-year basis, problems due <br />to aggradation could occur locally in the Canyon where there are low river <br />gradients over short reaches. <br /> <br />In summary, any change in river-streamflow regime or sediment supply will ,~ <br />cause adjustments in channe 1 hydraul i c characteri sti cs, and changes in the <br />variables of a river system will be such that hydraulic adjustment will be <br />minimized (Langbein, 1964). At best, only general predictions can be made <br />about the types of adjustments that will result from changes in hydrologic <br />conditions. By the same reasoning, it is difficult to identify precise levels <br />of reduced annual streamflow and anticipated sediment supply that will result <br />in minimal alteration of a river reach from its existing character. Estimates <br />of the sediment surplus or deficit at Deerlodge Park for several given <br />streamflow frequency di stri buti ons, and vari ous annual total sediment loads <br />and annual sediment supplies from upstream are given in the sediment budget in <br />table 6. The estimates are based on prevailing hydraulic conditions of slope, <br />channel geometry, velocity distribution, stage-discharge relation, sediment <br />discharge-water discharge relation, and sediment size. This table cannot be <br />used to predict specific or local geomorphic responses if the system is thrown <br />grossly out of balance, but it can be used as a management tool to identify <br />possib 1 e changes in channel equil i bri um resul ti ng from reduced mean-annual <br />streamflow or sediment supply. Other streamfl ow-durati on curves, such as <br />those based on streamflow requirements specified from biological studies, may <br />be substituted, in cQmputations to 'estimate annual sediment loads. Likewise, <br />sediment-supply scenlrios may be adjusted as more specific information becomes <br />available to identify the location and efficiency of potential sediment trap <br />areas in the Vampa basin. <br /> <br />SUMMARY AND CONCLUSIONS <br /> <br />The physical and biological character of the Yampa River i~ Dinosaur <br />National Monument primarily is controlled by the prevailing streamflow regime <br />and transported sediment, Pres<?rving the physical and biological environment <br />of the Vampa River through Deerlodge Park and Vampa Canyon will require main- <br />tenance of a range of streamflows for a given sediment supply over a,period of <br /> <br />30 <br />