Statistical charactersitics of fluvial displacements of individual particles

Sediment transport consists fundamentally of movements of individual particles. The motion of grains is not continuous, but consists rather of a series of steps and rest periods, either under the condition of partial or full mobility. Altogether, the movement of individual stones appears to be a statistically random phenomenon. Einstein's theory and subsequent similar approaches have attracted relatively little attention because of the difficulty of tracking suitably large samples of grains. In this study, a description of the statistics of the travel distance, step length, burial depth and virtual velocity of individual particles under range of sediment transport intensity regimes is presented. Published field data supplemented with new studies covering a wide range of flow and sediment supply regimes and channel morphology are analysed. The field studies are complemented by the analyses of flume data (Wong, 2007) collected under constant flow and varying hydrograph shape. Particle virtual velocity is linked to position within the active bed layer and fluctuation in bed elevation. On the basis of the available data, we aim at the development of a kinematic model that accounts for coarse gravel dispersion in gravel bed streams.