|Morphological management, a concept for a holistic management of estuaries|
Plancke, Y.; Ides, S. (2015). Morphological management, a concept for a holistic management of estuaries, in: International Conference Dunes and Estuaries 2015: Restoration of Tidal and Estuary Areas, Bruges, 16 -18 September 2015: proceedings. pp. [1-3]
In: (2015). International Conference Dunes and Estuaries 2015: Restoration of Tidal and Estuary Areas, Bruges, 16 -18 September 2015: proceedings. Flemish Government, Nature and Forest Agency: [s.l.].
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Over the past decades, several projects have been executed in estuaries without taking into account the possible effects on other estuarine functions. In recent years, due to the implementation of European Bird and Habitat Directives (Natura2000 sites), procedures have forced managers to search for a multifunctional approach. Where estuaries serve different functions (e.g. living, nature, port accessibility, fishery), the morphological evolution of the estuary is crucial with regard to the evolution of the various estuarine services, e.g. tidal penetration, occurrence of habitats, navigation. Managers should recognize the importance of morphology as it can be seen as the foundation for different functions.
In 2001 the Dutch and Flemish governments published a long-term vision (LTV) for the Scheldt estuary. That vision defined several goals focusing on safety against flooding, port accessibility and nature. Parallel with this LTV, an independent expert team, appointed by the Antwerp Port Authority, investigated the possibility of a navigation channel enlargement. They concluded that it was possible, although a new approach was necessary. Therefore they proposed a new strategy for the disposal of dredged sediment: based on their experience all over the world, they proposed to ‘use’ dredged sediment (sand) to create benefits for other functions (in casu ecology). Flanders Hydraulics Research investigated their idea and the feasibility of their concept was proved. It was finally incorporated in one of the alternatives within the environmental impact assessment of the channel enlargement in de Scheldt estuary, and was found to be the most environment-friendly alternative. Since 2010, dredged sediments have been disposed along different sandbars in the Westerschelde, changing the flow patterns and creating low dynamic habitats. Over the following years, ongoing monitoring should allow the evaluation of the success of this new concept on the longer term.
In finding the optimal management strategy for an estuary, policymakers have to deal with different functions, some having conflicting objectives. Morphology should be seen as the key for other functions, and morphological management the concept to realize win-win situations for different estuarine functions (‘holistic approach’). Although this concept may seem to be simple, several challenges remain: understanding of the morphological evolution is one of the more difficult scientific aspects; both numerical and physical scale models bring about important uncertainties, and experience is and will remain crucial in understanding the morphological functioning of estuaries.