| Biogeomorphodynamic model of Estuaries for the analysis of effects of human interference |
Period: January 2006 till December 2008
Status: Completed
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| Institute |
Top |
- University of Twente; Faculteit Construerende Technische Wetenschappen, more, executant
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| Abstract |
| Estuaries are important for economy and nature. Due to the relatively calm conditions where land meets the water, they are good locations for harbours and are safe havens and feeding grounds for wildlife. These qualities collide in the Western Scheldt. Dredging is required to enable navigation to Antwerp Harbour, but it endangers the stability of the shoals that are important to ecology. The interactions of the bed and the water flow over it shape the estuaries. The bed determines the flow of the water. In turn the water moves sediment resulting in bed changes. Stability analysis has shown that this feedback mechanism allows free instabilities to grow into a channel-shoal system. The essential processes for the morphology of estuaries are identified, but the long term dynamics of can only be modelled in idealised cases. Moreover, the problem is more complex. Sediment with much clay is cohesive; sediments with little clay are cohesive. The differences in stability of the sediment strongly influence the shape o f the shoals. Moreover, it has been shown that biology affects the morphology. Some organisms stabilise the bed, others have a destabilising effects. It is unclear yet, how these effects change the morphology of the channels and shoals. Cellular automata a re models that combine the essential mechanisms of a system with the freedom of randomness. The equations describing the essential processes make sure that the correct physics are simulated, while the random element allows free instabilities to grow. In this project the cellular automata approach is used to apply the existing knowledge gained by the stability analysis to existing estuaries. For this purpose the model parameters must be set correctly. Since many of the individual processes can not be measure d, the model will be tuned to field data of the bathymetry of estuaries and of the occurrence of biological organisms. |
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