Models of intermittent sediment transport near the threshold of motion

At low shear stresses, non-cohesive sediment transport near the bed is intermittent and driven by the dynamics of the turbulent boundary layer. By coupling a Lagrangian approach for the sediment grains with direct numerical simulations (DNS), Gonzalez et al., (2017) captured the particle dynamics in these conditions and calculated the transport in a small section of a bed with uniform diameter. Using this model, we can also yield insights on the physical mechanisms that control particle transport and the initiation of motion, and upscale the results to compute the bedload flux for different Shields numbers. In this work we also show the dependence of the continuum flux on the measurement timescale, and discuss the implications of intermittency of particle motion on the sediment transport flux, which can improve bedload predictions at larger scales.