Study of Friction Factors in the Upper Reaches of the Rio Grandeby Cassie C. Klumpp, (M.ASCE), U.S. Bureau of Reclamation, Boise, United States,
Drew C. Baird, (M.ASCE), U.S. Bureau of Reclamation, Boise, United States,
Document Type: Proceeding Paper
Part of: Hydraulic Engineering
The purpose of this study is to investigate the determination of Manning's roughness in the upper Rio Grande river basin and compare results to other studies where Darcy Weisbach friction factors have been determined for steep mountain streams. Three sites in the upper reaches of the Rio Grande have gradients that exceed 0.002 m/m: the Rio Grande at El Medio, the Rio Grande at the Vigil Ditch, and the Rio Grande at El Guique. The El Medio site has roughness elements that are very large in relationship to the depth. The Albuquerque Projects Office of the U.S. Bureau of Reclamation collected water surface elevations and discharge at these sites during the last 5 years. Manning's coefficients were calibrated at each site using the computer program STARCAL (Klumpp and Baird, 1993). STARCAL produces multiple water surface profiles for a reach until the RMS error of the measured and simulated water surface elevations are minimized. The selected roughness for the reach is obtained when the RMS error is minimized. The computed Manning's n was compared to Darcy Weisbach friction factors obtained by using different equations developed for large and intermediate scale roughness for steep gradient rivers. The equivalent sand grain roughness of the river was also examined.
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