Observations of suspended matter along the Dutch coast

Large amounts of suspended matter are transported through the Dutch coastal zone in the southern North Sea. Current estimates, based on budget studies, are in the order of 15-20 Mton per year transported in northward direction, which should take place in a small strip of 5-10 km wide. For this study we have performed a series of measurements on total suspended matter in an area in the most northerly extent of the Rhine region of fresh water influence. The measurements focused on observations both in the vertical and in the horizontal on the behavior of suspended matter in the nearshore zone up to 7 km from the shoreline. A peak in bottom concentrations is observed close to the coast along the coastal stretch. This hot spot location is found in the cross-shore direction at about 1.5 km from the coastline at a water depth of 15 m. Here, total suspended matter concentrations near the bottom exceed 200 mg/l. These peak concentrations have not been identified before and add to the suggestion that a large part of the northward suspended matter transport occurs very close to the coast.