Contact Load Model and Sediment Transport Due to Waves Versus Laboratory Data

A contact load layer model is presented, dealing with the effect of suspended sedi-ment on total sediment transport near the bed. The contact load layer is identified as the transition zone between the outer region (suspension layer) and the bedload layer. First, the physical aspects of momentum transfer arc discussed and the contact layer is defined. Further, following Dcigaard (1993) a new formulation of the skin friction being a combination of turbulence and the collisions between the grains, based on the diffusion concept, is postulated. Making use of the proposed solution procedure, the new system of equations is employed to compute time-dependent sediment con-centration and velocity, wave-period-average concentration and transport rate (net and average in ha^f period), together with the determination of two calibration coef-ficients, basically unknown in Dcigaard's (1993) approach. The bedload model of Kaczmarek ct al. (published simultaneously) provides the boundary conditions for the solution of the contact load layer. The comparisons between the model results and available laboratory data yield satisfactory conformity. Significant discrepancies between the model results and experimental data are found at higher levels above bed. They arc most probably linked to convectivc events in flow reversal.