Variation of Froude Number with Discharge for Large-Gradient Streams

by Kenneth L. Wahl, U.S. Geological Survey, Lakewood, United States,

Document Type: Proceeding Paper

Part of: Hydraulic Engineering


Under chemical-control conditions, the Froude number (f) for a cross-section can be approximated as a function of the ratio R2/ 3/d 1/2 , where R is the hydraulic radius and d is the average depth. For cross sections where the ratio increases with increasing depth, F can also increase with depth Current-meter measurement data for 433 streamflow gaging stations in Colorado were reviewed, and 62 stations were identified at which F increases with depth of flow. Data for four streamflow gaging stations are presented. In some cases, F approaches 1 as the discharge approaches the magnitude of the median annual peak discharge. The data also indicate that few actual current meter measurement have been made at the large discharges where velocities can be supercritical.

Subject Headings: Gaging stations | Froude number | Water discharge | Rivers and streams | Hydrologic data | Flow measurement | Cross sections | Water discharge measurement | Colorado | United States

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