Die Sedimentverteilung im Wattenmeer: Ein Simulationsmodell.

Natural mud flats and salt marshes are conspicuously rare along the modern Wadden Sea coast. Land reclamation and dike construction over the past 1000 years have recently been identified as the main cause for the depletion in fine sediment. The main objective of the present study is to quantify the magnitude of this man-induced loss, particularly with respect to the future development of the Wadden Sea in the course of continuing sea-level rise. In order to achieve this objective the sand fractions of the surficial sediments in the region were analysed in terms of settling velocity. Altogether the study is based on a data set of about 4800 samples collected in the Netherlands, Germany and Denmark. Settling velocities were measured by means of a high-resolution settling tube and were calculated for in situ winter temperature conditions. Finally, it could be demonstrated that a natural cliff can have the same impact on the coastline as an artificial barrier Iike a dike. Thus, the accommodation space for fine particles will be progressively 'squeezed' as long as sea level keeps rising, a consequence of higher energy levels at the foot of the barrier. Even a cursory glance at the literature reveals that the ecological impacts of this ongoing process have hitherto been largely underestimated, if at all recognised.