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<br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />II <br />I <br />!I <br />I <br />II <br /> <br />streams. The relationship developed is: <br /> <br />n = 0.39S0.38 R.-o.16 <br /> <br />where S is slope, (about 0.012 for the Dolores River at Rico) <br />R. is hydraulic radius (in feet) <br /> <br />Data from this study also support the assumption of subcritical flow conditions. Ranges <br />of roughness values for the main channels and flood plains are presented in Table 1-3. <br /> <br />Table 1-3. Manning's n-values used in this Study <br /> <br />typical Manning's "n" <br />maximum <br /> <br />Manning's "n" <br />minimum <br /> <br />Dolores River <br />main channel <br />flood plain <br /> <br />Silver Creek <br /> <br />0.055 <br />0.080 <br />0.120 <br /> <br />0.034 <br />0.060 <br />0.120 <br /> <br />0.070 <br />0.080 <br />0.120 <br /> <br />The flood profiles determined in this study assume that the channels and flood plains <br />remain unobstructed. Appendix A presents the input HEC-2 file and a summary of the <br />output. <br /> <br />References <br /> <br />1. The Early History of Rico - 1869-1886, The Dolores Star Press, 1964. <br /> <br />- <br />2. The Durango Herald, October 12, 1911. <br /> <br />3. The Dove Creek Press, October 13, 1911. <br /> <br />4. Colorado Historical Society negative #F36413, October 191 r, reproduced in A <br />Historic Touring Guide to the San Juan Skyway, by Ian Thompson, Fort Lewis <br />College, 1994. <br /> <br />5 <br />