AbstractIn order to evaluate the importance of differential transport velocities as a factor in sediment sorting by size and shape, transport velocities of individual size fractions in heterogeneous size mixtures of spherical glass beads and natural material were determined for different transport rates.Particle transport velocities in material of mixed sizes are shown to be significantly influenced by size and shape of the constituent particles. Maximum velocities occur in the intermediate size fractions for spherical glass beads and are displaced toward coarser fractions for natural material. Relative difference in transport velocities between size fractions may increase with increase in transport rate. The effect of particle shape on transport velocity decreases with increase in rate of transport. The results are tentatively projected to natural conditions, and novel solutions to some problems of sediment sorting are suggested. Particle settling velocity is found to be a well defined function of geometric particle shape, while transport velocity in bed contact motion correlates only poorly with the same shape index.