Recent morphologic evolution of the German Wadden Sea.

The Wadden Sea is a unique and important intertidal coastal zone under the pressure of changing driving forces (i.e. sea level rise, storm surges and increasing tidal range). In this study, we characterize the recent morphologic evolution of the German part of the Wadden Sea for the time period 1998 to 2016 based on a large dataset of available digital elevation models. A sediment budget analysis reveals that the Wadden Sea is accumulating sediment. Changes in the ratio of intertidal to subtidal surface area indicate an extension of the intertidal zone. Most of the intertidal flats accumulate sediments with rates higher than the observed mean sea level rise in the German Bight, while simultaneously the subtidal mean depth increases. For the period of investigation this Wadden Sea steepening is quantified to averaged values of +7.9 mm/yr for the tidal flats and -20.0 mm/yr for the channels.