This contribution is a remake of the one published under the same title by Reynolds (Nord. Hydrol., vol. 7, 1976, pp. 161-183). As in that paper, attention is given to the latest developments in the field of river morphodynamics and, in particular, on the formation of bed patterns. Stimulated by the work by Kidanemariam and Uhlmann (J. Fluid Mech., vol. 750, 2014, R2) the opportunity is taken to examine the most recent developments in terms of sediment transport models.