Page 31 - CBT 2018

Sand and gravel bedforms in rivers
Predicting the amount of sediment transported in a river during a flood event [is important for] hydraulic research and hazard mitigation. Sediment prediction is challenging mostly due to the migration of bedforms – the topographic elements that form the geometry of the river bed, such as ripples, dunes and bars – and the consequent hydrodynamic effects, in particular, friction and
form drag. Bedforms can change
in shape, wavelength, height, or migration speed, depending on flow discharge conditions and the material composition of the bed, which can vary from sand to gravel. The amount of sediment being transported (sediment mass flux) can be estimated by multiplying the mean amplitude of the bedform by its migrating velocity, or introducing Fourier decomposition and scale-dependent convection velocities to account for the variability and super-imposition of different bedform types and sizes, as demonstrated by recent experiments in CEGE hydraulic facilities. [45,46]
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