SEDYWA

Sediment exchange and dynamics between estuaries, adjacent mudflats and shallow water areas based on the example of the Elbe estuary

The aim of the SEDYWA project is to deepen the understanding of sediment exchange processes between estuaries and adjacent tidal flats and shallow water areas. The research focuses on the deposition and erosion behavior of fine sediments in the Elbe estuary.

At the end of 2013, concentrations of suspended solids in the tidal Elbe rose sharply, a trend that was reflected in significantly increased dredging volumes in subsequent years, including in the Port of Hamburg. Based on current knowledge, the sharp increase in suspended sediment concentration is attributed primarily to the remobilization of large quantities of fine sediments in the mudflats and foreshores of the Elbe estuary, mainly due to Storm Surge Xaver (Weilbeer et al. 2021). Despite the enormous significance of fine sediment dynamics in this area, there is currently little reliable knowledge regarding the details of exchange processes between the estuary and the mudflats or foreshores, or regarding the hydrodynamic conditions under which the mudflats in the Elbe estuary function as a source or sink for fine sediments. On the impact side, particular mention should be made of the bed shear stresses occurring (during extreme events), and on the resistance side, of the sediment composition and concentration near the interface—which are also insufficiently understood—as well as the associated erosion resistance. These knowledge gaps consequently lead to uncertainties in estimating the impacts of rising mean and extreme water levels resulting from climate change.

Within the framework of SEDYWA, these knowledge gaps—and thus the uncertainties—are reduced based on field measurements in representative mudflats, combined with laboratory investigations and theoretical and numerical analyses. In this context, the funding objective stated in the call for proposals—“quantification of sediment sources and sinks”—is explicitly addressed. A work objective is to directly link hydrodynamic loads on the one hand and morphodynamic responses on the other, both for individual extreme events and for average conditions (longer time periods).

The research results offer immediate practical and application potential for federal and state administrations and the scientific community through

i) an improved systemic understanding of the tidal Elbe and comparable estuaries

ii) the further development of hydro- and morphodynamic models based on the processed natural data, and

iii) insights into sustainable sediment management derived from these models