Laboratory experiments were undertaken in a unidirectional current flume in order to examine the role of turbulence on incipient sediment motion. An acoustic Doppler velocimeter was used to measure the instantaneous three-dimensional velocity components and acoustic backscatter (related to suspended sediment concentration). The relationship between wall turbulence (in particular, the "bursting" phenomenon) and resuspension of a non-cohesive sediment bed was examined. The results within a range above and below the measured critical velocity suggested that: 1) the contribution of turbulent bursting events remained identical in both experimental conditions; 2) ejection and sweep events contributed more to the total sediment flux than up-acceleration and down-deceleration events; and 3) wavelet transform revealed a correlation between the momentum and sediment flux in both test conditions. Such similarities in conditions above and below the measured critical velocity highlighted the need to re-evaluate the accuracy of a single time-averaged critical velocity for the initiation of sediment entrainment.
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