Impact of Back-Barrier Dams on the Development of the Ebb-Tidal Delta of the Eastern Scheldt

Abstract

Elekema, M.; Wang, Z.B., and Stive, M.J.F., 2012. Impact of back-barrier dams on the development of the ebb-tidal delta of the Eastern Scheldt.The Eastern Scheldt tidal basin in the SW part of the Netherlands has seen dramatic changes due to human intervention in the past few decades. The construction of two back-barrier dams in 1965 and 1969 had a significant impact on tidal hydrodynamics and sediment transport. The effects of these interventions were still ongoing when the hydrodynamic regime was altered again by the construction of the storm surge barrier between 1983 and 1986.This research describes the hydrodynamic and morphological evolution of the Eastern Scheldt ebb-tidal delta between 1960 and 1983, before construction of the storm surge barrier started. The analysis focuses on how the back-barrier dams changed the tidal flow on the ebb-tidal delta and how these altered hydrodynamics influenced sediment transport and morphology. It starts with a description of the observed hydrodynamic and bathymetric changes. These observations are used as input for a process-based numerical model (Delft3D FLOW), which is used to simulate situations before and after channel closures.In the decades before 1965, the Eastern Scheldt exported large quantities of sediment towards the sea through its inlet. The implementation of the dams caused a significant increase in tidal prism, which was observable in the response of the bathymetry; the export and the rates of channel deepening and ebb-tidal delta growth both increased. Analysis of tidal-flow measurements and model output show a persistent trend for sediment transport towards and out of the Eastern Scheldt inlet. The construction of the back-barrier dams only amplified this export by increasing the tidal prism and pushing the basin out of equilibrium even more than it apparently already was.