Resistance in Flat‐Bed Sediment‐Laden Flows

The effect on flow resistance in uniform flat‐bed open‐channel flows due to suspended sediment is investigated. Flows with and without an equilibrium sand bed are studied in a laboratory channel. Three well‐sorted natural sands are used. Point velocity measurements, as well as estimates of local wall shear, are obtained with a laser‐Doppler anemomentry system, and are used to evaluate friction factors. The results indicate that, contrary to recent models, the presence of suspended sediment does not necessarily lead to a reduction in flow resistance, but will generally result in an increase. The relation between changes in the velocity profile and changes in friction factors is discussed.