Laboratory measurements of bed load sediment transport dynamics

A video technique has been developed to study the motion of individual sediment particles under waves. The technique was developed for moveable bed conditions under waves in the Davidson Laboratory's large wave tank. Experiments were conducted with grain sizes of 1, 2, and 3 mm. All runs were applied to a modified Shields diagram and accurately predicted the region of motion and no motion. This proves that shear stress is an accurate predictor of grain movement initiation for a flat bed. The individual particle velocities were also measured. An ensemble average of particle velocity with respect to wave phase compared well with Sleath's expression for instantaneous bed load transport.