Changes in Coastal Morphological Processes Due to the Closure of Tidal Inlets in the SW Netherlands

Abstract

The closure of the Haringvliet and Grevelingen estuaries in 1970 and 1971 respectively, and the completion of the Oosterschelde storm surge barrier in 1986, have initiated a dramatic change in hydraulic conditions and in the geomorphology of the former ebb tidal deltas. The changes in coastal morphological processes have been studied by integrating the results of analysis of long-term field data and empirical and numerical morphological models. Here, a conceptual model of the dominant processes and actual sediment transport patterns of the former ebb tidal deltas in SW Netherlands is presented. After the in- and outgoing tides had been blocked, the exchange of sediment between the estuary and the ebb tidal delta has been disturbed. Under the prevailing wave and tidal conditions, the landward directed wave and tide induced sediment transport is no longer compensated by the seaward directed sediment transport. The general geomorphological response of the ebb tidal deltas to closure shows a net erosion of the delta fronts and relic tidal shoals, and a net sedimentation in the tidal channels and at the longshore bars near the edges of the ebb tidal delta. The adaptation of geomorphology to the changes in physical boundary conditions is continuing at a reducing rate.