Flow Depth in Sand‐Bed Channels

Six methods for predicting friction factor are evaluated and a new method is presented which better predicts flow depth (and therefore friction factor) when discharge and slope values are known. The goal of the investigation is to define a relationship between depth, discharge, and slope that can be used in a wide range of situations where uniform flow conditions are present, and which can also be adapted for numerical modeling applications. None of the six methods completely satisfy the writer's criteria; therefore a new relationship is presented. The proposed technique is based on dimensional analysis, a statistical analysis of a large body of laboratory and field data, and basic principles of hydraulics. Separate equations are developed for the lower (dune and ripple) and upper (flat bed and antidune) flow regimes. The technique also includes a simple method for flow regime determination. Finally, the proposed method is verified through comparison with data sets not used in the derivation of the technique.