A synthesis on the assessment of an alternative disposal strategy to serve sustainability in the Scheldt estuary
Roose, F.; Plancke, Y.; Ides, S. (2008). A synthesis on the assessment of an alternative disposal strategy to serve sustainability in the Scheldt estuary, in: CEDA Dredging Days 2008: Dredging facing Sustainability, Antwerpen (Belgium), October 1-3, 2008. pp. [1-13]
The Scheldt estuary is characterised by a valuable multiple-channel system consisting of sandbars in between primary and secondary channels. Within the framework of the Long Term Vision (LTV) for the Scheldt estuary the conservation of this multiple-channel system is defined as the key goal to achieve morphological sustainability. Dredging is one of the human activities having an impact on morphology, hence dredging and disposal should be optimised by minimising the negative impact on morphology. The current disposal strategy for maintenance dredging consists mainly of disposing sediment into the secondary channels. As a consequence of the sustainability goal a maximum dumping capacity is assigned to each secondary channel in order not to exceed the natural bearing capacity of the multiple-channel Scheldt estuary. The assigned yearly disposal capacity for all secondary channels together is sufficient to counter the yearly sediment volume arising from maintenance dredging operations. However, if the total sediment volume that is produced by the deepening of the navigation channel towards Antwerp would be disposed into the secondary channels, the conservation of the multiple-channel system would not be guaranteed. To anticipate on this expectation, shallow water sandbar slopes have been proposed as an alternative disposal location. The use of these alternative disposal locations provides an increase in the estuary’s disposal capacity without increasing the disposal intensity in the secondary channels and is expected to enlarge the area of shallow water habitats, creating opportunities for ecosystem development. The feasibility of this proposal has been investigated by desk studies on historical maps, by field measurements, by physical scale model tests and by numerical simulations and has been confirmed by two in situ experiments. Consequently, the alternative disposal locations will be used during the deepening of the navigation channel towards the port of Antwerp. As a result of the adaptation of the disposal strategy, the conservation of the valuable multiple-channel system in the Scheldt estuary is not endangered by dredging and disposal operations.
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