Physical Processes Driving the Morphological Evolution of the Roggenplaat Tidal Flat

Abstract

The flow velocities in tidal channels are already rather complex by the presence of various tidal components, wind driven flow and estuarine circulations. An extra level of complexity is introduced when the flow on top of an intertidal
flat is considered (Le Hir, 2000). This research aims at understanding the complex flow patterns on top of a large-scale intertidal flat and on assessing the morphological consequences. The focus of this study is on the Roggenplaat, which is with an intertidal area of 14.6 km2 the largest intertidal flat
fully surrounded by channels of the Eastern Scheldt (The Netherlands, see Figure 1). The flat is subject to a mean tidal range of 2.6 m and is characterized by a typical sediment grain size of 0.25 mm. Two large tidal creeks in the Northwest
are the remainder of the merging of separate flats 80-150 years ago. Since the late 1980s, the flats in the Eastern Scheldt have been eroding severely because of the construction of a storm surge barrier and various compartment dams (Louters, 1998). A nourishment of 1.65 million m3 is planned on this flat for 2017, to compensate for its lowering. This study combines the results of an Acoustic Doppler Current Profiler (ADCP) measurement campaign with the results of a numerical model. Apart from validation material for the numerical model, the ADCP data is also analysed individually. The focus of this study is on the present-day hydrodynamics and morphodynamics of the Roggenplaat, which is essential knowledge for the design of appropriate nourishment strategies. Furthermore, physical insights achieved in this study are relevant for the understanding of other large-scale intertidal flats around the world.