conceptual framework for fine sediment dynamics in the Scheldt estuary : providing a framework for data and model analyses and impact assessments

In the Scheldt estuary, located in the Netherlands and Flanders (Belgium), authorities cope with several problems and challenges associated to fine sediment dynamics. These are related to dredging, turbidity, and development of intertidal areas and salt marshes. These issues are typical for other estuaries with large ports around the world, in densely populated areas. Sustainable management of the estuary means that interventions are within the limits of resilience of morphology and ecology, and/or safe operating space. This requires system understanding, which can be brought together into a conceptual model. The presentation, discussion and application of such conceptual model for fine sediment dynamics in the Scheldt estuary is the objective of this report. It is based on a decade-long experience from monitoring, modelling and analysis of fine sediment dynamics in the Scheldt (in the framework of VNSC studies) and beyond. Using the framework that this conceptual model provides, the impact of several human interventions on fine sediment dynamics are assessed, such as maintenance dredging and disposal of harbor mud, channel deepening and the removal or addition of intertidal areas. Based on this impact analysis, remaining data and knowledge gaps are identified and how the reduction of these gaps can reduce the uncertainty of future impact assessments. This provides guidance on future monitoring, modelling and analysis efforts. The system understanding on long time scales, when a combination of changes in hydrodynamic forcing, mud availability and mud properties play a role, should be improved. In order to do so, existing observations on SPM dynamics at tidal, seasonal and long-term scale should be accompanied by more long-term observations on mud accretion, mud properties and vertical profiles of bed composition.