Bram van Prooijen (TU Delft)
Lodewijk de Vet, Irene Colosimo, Marco Gatto, Cynthia Maan, Zheng Bing Wang (TU Delft)
Tom Ysebaert, Brenda Walles (NIOZ)
The morphology of tidal flats is affected by human interferences within the estuarine systems, like channel deepening, land reclamation and building of dams and/or storm surge barriers. These effects are superposed on the ongoing “autonomous” morphological behaviour of the tidal flats.
In the Netherlands, we can identify various types of estuarine systems that are influenced by human activities. The Oosterschelde (Eastern Scheldt) is a semi-enclosed basin that is closed off from the sea during storms by a storm surge barrier (since 1986), but the barrier is open during calm conditions. The barrier however resulted in a significant reduction in tidal volume during normal conditions. The Westerschelde (Western Scheldt) is the gateway to the port of Antwerpen (Antwerp/Anvers). The channels have been deepened in the past and are continuously dredged. Part of the Wadden Sea has been closed off by the Afsluitdijk in 1932. The morphology and sediment distribution of the Wadden Sea is still adapting.
As all these estuaries host important habitats (Natura2000, the Wadden Sea is even World Heritage), coastal management needs to preserve these areas. Preservation requires action as some tidal flats are drowning or reducing in size. Various mitigation measures have been proposed and some are in the pilot phase, where other measures are already common practice.
In this presentation, I give an overview of these three different estuarine systems with their specific morphological (and partly ecological) evolutions and ongoing mitigation strategies. Various tidal flats will be discussed to see whether they are in or out of equilibrium, and why that is the case (we don’t have explanations for all flats yet). Research by means of analysis of historical data sets, ongoing field campaigns and numerical models will be shown. One of our goals is to determine if tidal flats can be in (multiple) equilibrium state(s) and whether human interferences can change the equilibrium state. We would like to compare the behaviour of our flats with the flats in the French systems to increase our generic understanding of tidal flat morphodynamics. Furthermore, we are interested which human interferences affected the French tidal flats and whether negative trends are mitigated.