The rate of fluvial gravel dispersion



[1] Sediment dispersion is a fundamental process embedded in the bedload of rivers but the rate at which it occurs is poorly known. This study quantifies the streamwise and vertical dispersion rates of gravels over a long flood sequence by using magnetically tagged clasts. Both grain virtual velocity and grain burial rate decline rapidly as a function of expended flow energy and attain limiting values that are a small proportion of initial rates. Differences between grain sizes lessen over time as equilibrium rates of dispersion are achieved. Relative rates demonstrate that streamwise dispersion dominates over vertical dispersion, although the latter persists as an essential part of the dispersion process.