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1 lJ 1 1 1 1 1 1 1 1 1 1 Memorandum to Henry Bazbe, MCC July 28, 2000 Page 3 assigned values the average velocity can be computed by use of Manning's Equation for turbulent flow as follows: v _ 1.486 R~S~ 1 J 2 / h / + n where: v =velocity, ft/sec Rh =hydraulic radius, approximated as the depth, = 1.0 ft St =friction slope, approximated as the water surface slope, = 0.049 fr/fr n = Manning's "n" roughness coefficient = 0.065 Applying Manning's equation the velocity for the dominant dischazge is 5.1 fr/sec. With the assumed hydraulics, the critical velocity for dominant discharge is 5.8 ft/sec, which provides good support for subcritical flow with a 5.1 fUsec velocity. A summary tabulation of the channel hydraulic characteristics for the Deep Creek study reach at dominant discharge are: Discharge cfs Width ft Depth ft Slope ft/fr Velocity ft/sec 55.6 9.0 1.0 0.049 5.1 A test for possible predictive purposes was the application of the Leopold Equations for the hydraulic characteristics. Leopold describes a stable channel configuration by the follo+ving relationships: w=aQh d=cQf v=kQm (2) where: +v is width. Q is discharge, d is depth, v is mean velocity, the letters b, f, m are exponents, and a, c, k are coefficients. In these three relationships, Q = w*d*v and, thus, the sum of the exponents is one. The most common values for these exponents are b = 0.50, f = 0.40, and m = 0. ] 0. Coefficients used on man}~ streams in the Colorado area are, a = 2.7, c = 0.14, and k = 2.5. Based on the dominant discharge hydraulics, the coefficients for Deep Creek are, a = 1.5, c = 0.20, and k = 3.4. SEDIMENT YIELD An estimate was made of the average annual sediment load of Deep Creek through the study reach by use of the methods described in the report by John G. Elliott, "Regionalizztion of Mean Annual Suspended-Sediment Loads in Streams, Central, Northwestern and Southwestern Colorado," a 1988 U.S. Geological Survey, Water-Resources Investigations Report 87-4193. A Wright Water Engineers, Inc , 2490 W. 26°' Avenue, Ste. 100A, Denver, CO 60211 7e1. 303/460-1700; Fax. 303/460-1020, e-mail:knvright~vrtightwater corn 1