| dc.description.abstract | The Nieuwe Waterweg is a heavily engineered estuary that forms the entrance to the Port of
Rotterdam. To allow easy access for increasingly larger ships to the harbours, the Nieuwe Waterweg has been narrowed, straightened and embanked and the bed is continuously dredged
to an unnaturally deep water depth. This has led to increased flood risks, salt intrusion and
ecosystem degradation in the area and these issues are expected to worsen with sea level
rise. To counteract these issues, it has been proposed to stop dredging and let the channel
become shallower through natural sedimentation processes. However, it is unknown how the
morphology would develop through natural sedimentation-erosion patterns due to the unnatural planform shape of the estuary. In this study, the morphological development of the
Nieuwe Waterweg without dredging was simulated in the Metronome, a periodically tilting
tidal flume capable of creating dynamic estuaries. Three experiments were performed to investigate how a harbour complex and mud supply influence the sedimentation-erosion patterns.
The bed elevation was measured during the experiments to analyse the development of the
sedimentation-erosion patterns. In addition, the hydrodynamics of the water flow in the experiments were measured and simulated with a numerical model, XBeach. Due to the fixed
planform shape the morphology in the experiments developed in the vertical instead of the
horizontal as in natural estuaries. This resulted in a pattern of increasing landward shallowing
by net sedimentation and seaward deepening by net erosion in all experiments. The harbour
complex acted as a sediment trap in both experiments, with most sedimentation in the case
of mud supply. In general, the mud deposited mostly in inactive areas, on top of bars and in
the landward end of the estuary. In reality the same general pattern of landward shallowing
and seaward deepening is expected to develop. However, due to the large water depth in the
Nieuwe Waterweg, this is expected to develop by increasing amounts of landward sedimentation only. This development would have large consequences for the accessibility for ships
and thus harbour industry. However, it would also counteract salt intrusion, decrease flood
risks and provide new areas for nature restoration which could turn the harbour areas into
new attractive living and working spaces. | |
