Are Wadden Sea tidal systems with a higher tidal range more resilient against sea level rise?

Abstract

Accelerated sea level rise may have serious implications for the Wadden Sea ecosystem in its present state. If sediment accumulation rates on the extensive intertidal flats stay behind sea level rise, the flats will eventually submerge. Drowning of the flats has negative consequences for nature conservation and for coastal risk management. Based upon an evaluation of steady state relations for Wadden Sea tidal basins, Hofstede (Zeitschrift für Geomorphologie 59(3): 377-391, 2015) postulated that the capacity of these basins to balance sea level rise by accumulation on intertidal flats seems positively related to mean tidal range. In the present study, morphodynamical simulations with a numerical model were performed for two tidal basins in the German Wadden Sea to verify the empirically established hypothesis. The following conclusions are established. Larger mean tidal range improves the capacity of Wadden Sea tidal basins to balance sea level rise. Wadden Sea intertidal flats are effective sediment sinks and seem quite resilient against (higher rates of) sea level rise. Finally, subtidal gullies may constitute a significant sediment source for accumulation on intertidal flats in response to sea level rise. With respect to the limited comparability of the two investigated tidal systems, morphodynamical modelling of all Wadden Sea tidal systems should be conducted.