| abstracts | A contact load layer model is presented, dealing with the effect of suspended sediment 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 are discussed and the contact layer is defined. Further, following Deigaard (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 concentration and velocity, wave-period-average concentration and transport rate (net and average in half period), together with the determination of two calibration coefficients, basically unknown in Deigaard's (1993) approach. The bedload model of Kaczmarek et 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 level above bed. They are most probably Jinked to convective events in flow reversal. |