Sediments and suspended matter in the sylt-Rømø tidal area: A summary of Results Collected in the “SWAP”-project

Abstract

The Sylt-Romo tidal basin has evolved during the last 5000 to 5500 years. In 1992 it covered 401.4 km z, of which 60O/o were subtidal areas and 40% were intertidal flats. With the beginning of the last century reliable maps became avai[able fbr this part of the Wadden Sea. Since that time significant losses of sediment in subtidal areas can be demonstrated.The main part (114.7 km 2, 72%) of the intertidal flats is built up of sand. Sandy deposits also prevail in the subtidal areas. Muddy sands with 10 to 50O/o silt and clay forma nearshore, more of less narrow belt along the islands, dams and main land coasts. They cover 39 km 2 or 250/o of the intertidal region. Muddy intertidal flats and salt marshes enclose less than 10 km 2 each. This sediment distribution partero exhibits the typical zoning of the dep• in an intertidal bay. The spatial distribution of the fine-grained suspended sediments largely fbllows this pattern. In the Sylt-Romo tidal area the net accumulation rate ofthese sediments ofabout 58000 t/a is relatively low. Dieses Sedimentverteilungsmuster gibt die typische Zoniemng einer Bucht des Gezeitenbereiches wieder. Die r/iumliche Verteilung der supendierten, feink6migen Sedimente folgt ira wesentlichen diesem Muster. Die Ablagemngsrate derartiger Sedimente ira Syh-Romo Wattenmeer ist mit 58000 t/a vergleichsweise gering.