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The distribution of suspended matter in the Dutch coastal zone
Visser, M.; de Ruijter, W.P.M.; Postma, L. (1991). The distribution of suspended matter in the Dutch coastal zone. Neth. J. Sea Res. 27(2): 127-143
In: Netherlands Journal of Sea Research. Netherlands Institute for Sea Research (NIOZ): Groningen; Den Burg. ISSN 0077-7579, more
Peer reviewed article  

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  • Visser, M.
  • de Ruijter, W.P.M.
  • Postma, L.

    Results are presented of suspended matter observations taken at bi-weekly intervals during the period 1975-1983, in a strip 70 km wide along the Dutch coast. The average distribution showed a (weak) minimum zone located north of Noordwijk at a distance of about 30 km from and parallel to the Dutch coast, between the salinity maximum and the coast. Variability was large between different years, seasons and individual cruises. A clear seasonal cycle emerged from the observed suspended-matter patterns: in winter a pronounced minimum existed, while in summer generally a monotonically decreasing concentration was measured, to open-sea values much lower than in winter. This seasonal cycle may be explained by a combination of variation in wind, river discharge and the activity of suspended-matter sources. The Flemish Banks and Channel waters are the main sources supplying suspended matter to the Dutch coastal area. Especially the varying transport through the Strait of Dover, large in winter, small in summer, determines the seasonal variation in the total amount of suspended matter. The existence of a localized turbidity minimum is tied to relatively large discharges from the Rhine and associated steep salinity gradients, also occurring mainly in winter and early spring. A simple model of cross-shore density-driven circulation shows the possible influence of the strong salinity gradients on the sedimentation of suspended matter. Particles with a settling rate comparable to the vertical velocity component of the circulation are forced to move offshore until they reach an area where they sink out of the surface layer. The strength of this circulation is determined by the cross-shore density gradient due to the inflow of fresh water from the Rhine-Meuse estuary.

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