Calibration of Manning's Roughness for a River Reach

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by Cassie C. Klumpp, U.S. Bureau of Reclamation, Boise, United States,
Drew C. Baird, U.S. Bureau of Reclamation, Boise, United States,

Document Type: Proceeding Paper

Part of: Hydraulic Engineering

Abstract: The Albuquerque Projects Office of the U.S. Bureau of Reclamation collected water surface elevations for measured discharges for the Rio Grande and many of its tributaries to try to obtain a record of river hydraulics for the purpose of calibrating Manning's roughness coefficient. The Albuquerque Projects Office in the past calibrated a river reach manually by estimating a Manning's roughness for a reach and computing a water surface profile for the reach. The root mean square (RMS) error was then calculated by computing the difference between the measured and computed water surface elevations and adding the error and dividing by the number of measurements and computing the square root. This method was repeated until the minimum root mean square error was calculated for the reach for a given roughness coefficient. STARCAL is a computer program created from the STARS program (Orvis and Randle, 1987) for a reach. The user enters a best estimate for the roughness for the reach. The user also supplies factors to vary the Manning's n for the reach. The program runs multiple water surface profiles for the river reach computing the RMS error between the measured and computed water surface elevations for a given discharge. The roughness is obtained when the RMS error is minimized.

Subject Headings: Hydraulic roughness | Rivers and streams | Errors (statistics) | Calibration | Computer software | Water surface | Computer models | Water discharge measurement | North America | Albuquerque | United States | New Mexico | Rio Grande

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