Bar Resistance of Gravel-Bed Streams

Gravel-bed streams with bankfull channels of low sinuosity are considered. At flood stages, most of the resistance is grain resistance. Thus, depth-discharge relations can be predicted with existing method, although the inherent scatter is large. At lower stages, however, from resistance due to the presence of bars becomes increasingly important. Bar resistance is quantified empirically using data from rivers in Alberta, Canada, and the device of slope division of reach-averaged bed stress. Further reduction leads to predictive design graphs for depth-discharge relations. A numerical example is provided.