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Modeling mussel bed influence on fine sediment dynamics on a Wadden Sea intertidal flat

Leeuwen, B. van (2008) Modeling mussel bed influence on fine sediment dynamics on a Wadden Sea intertidal flat.

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Abstract:Large aggregations of mussels, so called mussel beds, live in the Dutch Wadden Sea and the Eastern Scheldt estuary. Mussel beds can be hundreds and even thousands of meters in size. The influence of mussel beds on fine sediment dynamics has been well recognized in literature. Until now, no successful attempts at modeling this influence exist. During this study a process-based model implementation of young mussel bed interaction with fine sediment has been set up for use in Delft3D. Roughness and erosion behavior have been implemented via the Delft3D trachytope functionality. The Delft3D source code has been adjusted in order to simulate active capture of suspended fine sediment by mussel filter feeding. The properties of sediment (including pseudo-faecal matter) deposited in between mussels have been taken into account by adjusting the sediment characteristics in the mussel bed. The mussel bed implementation has been tested in a Wadden Sea intertidal mudflat model. The model domain has been based on an area south of Ameland, which is suitable mussel habitat. The model has simulated two current dominated summer months. A sensitivity analysis has been conducted on the parameters of the mussel bed implementation. Finally, different patterns, known to occur in young mussel beds, have been imposed. It has been concluded that roughness and filtration rate of mussel beds are important factors in mussel bed influence on fine sediment. A combination of active deposition via filtration and slowdown of the flow leads to high cumulative deposition in the mussel bed. In the surrounding area deposition is also high because of a reduction of flow velocities caused by the rough mussel bed. Patchiness and specifically striped patterns in mussel bed coverage cause mussel beds to experience less sedimentation than uniformly covered beds of the same size. In a broader sense, it has been found that the ability of young mussels to quickly climb on top of deposited material, results in rapid capture and trapping of large amounts of fine sediment.
Item Type:Essay (Master)
Faculty:ET: Engineering Technology
Subject:56 civil engineering
Programme:Civil Engineering and Management MSc (60026)
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