Resuspension, Sediment Fluxes, and Suspended Sediment Diffusion Coefficients under Wave and Current Forcing in Two Coastal Environments

Geografisk Tidsskrift, Danish Journal of Geography 98: 10–19. A stainless steel tripod equipped with five sediment traps placed at 0.35 m intervals above the seabed was deployed both in wave and current dominated shallow water environments. The length of tripod deployments varied between three and seven days. Sedimentation fluxes during resuspension in the wave-dominated environment ranged from 24.1 g m−2 day−1 at 1.75 m to 36.4 g m−2 day−1 at 0.35 m. In the current-dominated environment the fluxes ranged from 5.2 g m −2 day−1 at 1.75 m to 573.0 g m −2 day−1 at 0.35 m. Maximum shear stresses during the resuspension events in each of the two environments were of similar size, 0.042 and 0.06 N m −2, respectively. Additional deployments of the tripod during periods with low current speeds and no surface wave activity showed that the primary sedimentation varied between 3.0 g m −2 day−1 and 10 g m −2 day−1 in both environments. Sedimentation flux variation with height above the seabed was very small in the wave environment and large in the current environment during periods of resuspension. The increasing vertical component of the wave orbital movement with height above the seabed in the wave-field, together with differences in grain-sizes between the two environments are the main explanations for the observed differences in vertical fluxes. Diffusion coefficients of suspended particulate matter, K s, in the two environments were estimated on the basis of the measured sedimentation fluxes. Observed Ks was on average 92 times larger in the wave environment than in the current environment. Theoretical results of Ks were consistent with observations of Ks in the current dominated environment if the ratio Ks/Km ≈ 0.2 where Km is the diffusion coefficient of momentum. Theoretical and observed Ks in the wave environment were only of similar size close to the seabed. Keywords: Coastal environmentssedimentation fluxesresuspensionsediment trapswave-fieldcurrent-fieldsuspended sediment diffusion coefficients

Atmospheric sciences · Current (fluid · Diffusion · Forcing (mathematics · Geomorphology · Geotechnical engineering · Hydrology (agriculture · Physics · Sediment · Sediment transport · Coastal and Marine Dynamics · Coastal wetland ecosystem dynamics · Environmental Science · Geology · Oceanography · Tropical and Extratropical Cyclones Research

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