Mud Disposal And Suspended Sediment Concentration In The Lower Sea Scheldt - Towards A Hyperturbid System?

In this paper, an analysis of continuous SSC measurements in the Sea Scheldt is presented. Information from different projects that focus on the state of the Scheldt Estuary (Belgium-Netherlands) and the management of dredging and disposal activities, is discussed to increase the insight in the effects of mud disposal and the increasing sediment concentrations (SSC) in the Lower Sea Scheldt.A positive feedback loop has been hypothesized and supported by observations in several estuaries, showing that an increase in tidal amplitude may lead to an increase in sediment concentrations, decrease of hydraulic drag resistance and again in tidal amplitude increase. Estuaries that have undergone such transformations are now characterized by hyperturbid conditions, the presence of fluid mud layers and ultimately, a poor ecological state. The feeds to the positive feedback loop appear to be present in the Lower Sea Scheldt as well: increase of tidal amplitudes in the past decades, and more recently changes in SSC.Although the long-term trend may still not be revealed, it is shown that mud disposal in the Low Sea Scheldt influences SSC in a larger area. Increased mud disposal leads to rather immediately elevated SSC values. On the other hand, a decrease of mud disposal also resulted in decreased SSC values. It is therefore suggested that future sediment management choices will partly determine whether SSC will continue to rise in the Sea Scheldt.