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The mechanics of suspended sediment under wave action are investigated. The results apply to regions well beyond the surf zone where the flow field, though irregular in appearance, is still amenable to mathematical expressions in gross terms. The motion of the suspended sediment particle and that of the fluid particle in a wave field are found to have an amplitude difference and a phase lag. The suspended sediment concentration is a hyperbolic trigonometric function of water depth. The relation reduces to a power law for shallow water cases. The value of power is found to be a function of particle settling velocity, fluid particle velocity, and wave number. Wave mass transport velocity is derived on the basis of turbulent boundary layer as the lower boundary condition. Finally, it is found that the rate of suspended sediment transport in a wind‐generated random wave field can be approximated by a power function in terms of wind velocity.

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Sediment transport in random waves at constant water depth is analyzed by dividing the flow field into two regions—the internal region and the boundary layer region. The suspension and transport of sediment in these two regions are treated separately. The total transport is then obtained as the total of these regions through matching boundary. In the bed layer, the load concentration is assumed to be proportional to the specific weight of the sediment and to the probability that the fluctuating lifting force exceeds the weight of the sediment. The bed load is then transported by the secondary flow (which is unidirectional) in the boundary. In the internal flow region, the sediment suspension is treated as a diffusion problem with the intensity of diffusion to be proportional to the amplitude of fluid particle motion. The transport velocity is assumed to be the same as the mass transport velocity of the wave. The predominant mode of transport is found to be suspended load. The total transport in a wind-generated wave field can be expressed as a power law of wind speed. For the case tested, the power should be of the order of 4.

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