Development of a video technique to study bed load sediment transport

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 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 (1986) expression for instantaneous bed load transport. Particles of this size lead the free stream velocity by approximately 25° and travel at approximately 30% of the free stream fluid velocity. Additional experiments were conducted to study the motion of particles under waves with no intergranular forces affecting the motion of the particles. An equation of motion for a sediment particle under waves, offered by Grant and Madsen (1982), was used to predict the sediment particles acceleration.