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14 <br />Below whirlpool Canyon, the river meanders for seven miles through an <br />open valley of Quaternary alluvium and a few exposures of Mesozoic <br />sandstone. The sinuosity of this reach is high (1.90) and the gradient <br />averages less than one ft./mile. The channel is wide and braided, forming <br />several islands. The occurrence of several intermittent and extinct channels <br />indicates the dynamic nature of the river through this section. <br />In its final eight miles within the Monument, the river flows through <br />Split Mountain, a continuation of the Uinta uplift, and then leaves the <br />uplift for the broad alluvial valleys to the south. Z'he canyon through <br />Split Mountain is relatively straight. The high river gradient (17.9 <br />f t./mile) produces a swif t current and several rapids. <br />Flow Regimes <br />The Yampa River <br />Immediately above the eastern Monument boundary, the Yampa is joined <br />by the Little Snake River from the north. The Yampa above the Little Snake <br />drains approximately 3400 sq. miles. The drainage basin of the Little <br />Snake is aout 3700 sq. miles. Although it has a larger drainage basin, the <br />discharge from the Little Snake is generally lower than that of the Yampa <br />above their confluence due to the generally lower elevations and <br />precipitation of its headwaters. <br />Flow data are available from U.S. Geological Survey gauging stations <br />on the Yampa at Maybell, Colorado (approximately 20 miles above the <br />confluence with the Little Snake) and on the Little Snake at Lily, Colorado <br />(10 miles above the confluence). These records date from 1916 and 1921, <br />respectively, and include daily discharge data since the 1950s (USGS 1961 to <br />present, 1964 to present). <br />