Where overland flow velocity is measured using dye or salt tracing, the mean velocity is often determined by multiplying the velocity of the leading edge of the tracer plume by a correction factor &agr;. Flume experiments show that &agr; varies with both Reynolds number and sediment load. For sediment-free flow over a sand-covered bed, &agr; is less than the theoretical value of 0.67 in laminar flow and increases rapidly with Reynolds number in transitional flow and more slowly with Reynolds number in turbulent flow. For sediment-laden flow, &agr; decreases as sediment load increases in transitional and turbulent flows. Saltating sediment extracts momentum from the flow, causing velocities near the bed to decrease and &agr; to decrease. A multiple-regression equation is developed which can be used to predict the value of &agr; from Reynolds number and sediment load in transitional and turbulent overland flows.¿ 1997 American Geophysical Union