Sandwave migration is observed in the Marsdiep inlet (tidal inlet between the Wadden Sea and the North Sea). Hourly measurements with an Acoustic Doppler Current Profiler (ADCP) mounted under a ferry give us an estimation of the sandwave migration in the inlet. Physical processes responsible for the sandwave migration are different tidal components, a residual component as well as the phase different between the tidal components. Decelerating of the near-bed flow by tube building worms on the bottom of the seabed is characteristic for biological activity in the study area. By including both the physical and biological processes in an idealized model, we are able to (1) reproduce the sandwave migration in the inlet and (2) determine the contribution of the different physical and biological processes on the spatial variation in sandwave migration. The residual current is mainly responsible for the migration of sandwaves. However, for large values of the quarter-diurnal tidal component (M4), sandwaves also migrate against the residual current. Biological activity is shown to significantly influence the wavelength of sandwaves, and only have a small contribution to the spatial variation in migration of sandwaves, compared to the physical processes.
Bio-geomorphological interactions in sandwave migration
BESIO, GIOVANNI;
2009-01-01
Abstract
Sandwave migration is observed in the Marsdiep inlet (tidal inlet between the Wadden Sea and the North Sea). Hourly measurements with an Acoustic Doppler Current Profiler (ADCP) mounted under a ferry give us an estimation of the sandwave migration in the inlet. Physical processes responsible for the sandwave migration are different tidal components, a residual component as well as the phase different between the tidal components. Decelerating of the near-bed flow by tube building worms on the bottom of the seabed is characteristic for biological activity in the study area. By including both the physical and biological processes in an idealized model, we are able to (1) reproduce the sandwave migration in the inlet and (2) determine the contribution of the different physical and biological processes on the spatial variation in sandwave migration. The residual current is mainly responsible for the migration of sandwaves. However, for large values of the quarter-diurnal tidal component (M4), sandwaves also migrate against the residual current. Biological activity is shown to significantly influence the wavelength of sandwaves, and only have a small contribution to the spatial variation in migration of sandwaves, compared to the physical processes.
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