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<br />- <br /> <br />SEDIMENT TRANSPORT IN THE LOWER YAMPA RIVER, <br />NORTHWESTERN COLORADO <br /> <br />By John G. Elliott, James E. Kircher, and Paul Von Guerard <br /> <br />ABSTRACT <br /> <br />Di scharge measurements and sedi ment samples were taken at streamflow,:" <br />gaging station 09260050 Yampa River at Deerlodge Park in 1982 and 1983 to <br />determine the average annual sediment supply to the Yampa Canyon in Dinosaur <br />Nat i ona 1 Monument. Daily mean di scharge recorded at the Deerlodge Park gage <br />correlated well with the sum of daily mean' discharges recorded at two, <br />streamflow-gaging stations in the dra'inage basin upstream: Station 09251000 ' <br />Yampa River near Maybell, and station 09260000 Little Snake River near Lily. <br />Because of good correlation of discharges recorded during the study period <br />(R2=0.98), 43 years of discharge records at the two tributary sites were <br />combined to determine the historic discharge of the Yampa River at Deerlodge <br />Park. An historic average hydrograph and a flow-duration curve were derived <br />from the combined discharge data. <br /> <br />Sediment-transport equations were derived for total sediment discharge, <br />suspended-sediment discharge, bedload discharge, and the discharge of sediment <br />in several particle-size ranges. Annual sediment discharges were determined <br />by the fl ow-durat i on, sediment-rati ng-curve method. These computations <br />i ndi cated that mean annual total sediment di scharge was approximately 2.0 <br />million tons per year of which 0.8 million tons ~er year was sand-size materi- <br />al. Bedload was almost entirely sand, and mean annual bedload discharge was <br />0.1 million tons per year. <br /> <br />Development of water resources in the Yampa River basin could have <br />considerable effect on the geomorphic and biological character of the Yampa <br />River at Deerlodge Park 'and through the Yampa Canyon. In this report, several <br />scenarios of altered streamflow frequency distribution, reduced streamflow <br />volume, and reduced sediment supply are examined to estimate the effect on the <br />sediment budget at Deerlodge Park. <br /> <br />INTRODUCTION <br /> <br />Cllannel morphology as well as the aquatic and riparian habitat of t'he <br />Yampa River in Dinosaur National i10nument is primarily controlled by the <br />prevailing streamflow regime and transported sediment. The river channel will <br />adjust to significant long-term changes in the total volume of annual <br />streamflow, the range of discharge, the sediment supply, or the particle size <br />of sediment. Water resource development in the Yampa River basin could lead <br />- <br /> <br />1 <br />