Mussel beds are known to affect fine sediment dynamics and morphology on mudflat scale, a clear example of ecosystem engineering. Current research into possible ecological engineering applications of mussel beds makes quantitative modeling desirable. In this study a process-based model of the interaction between a young mussel bed and fine sediment was set up for use in the hydrodynamic and morphological model Delft3D-FLOW. The model encompasses the hydraulic roughness of the mussel bed, active capture of suspended sediment by filter feeding and changed bed properties due to biodeposited matter. The mussel bed implementation in Delft3D-FLOW was applied in a test case: a Wadden Sea intertidal mudflat model. It was concluded that a combination of active deposition via filtration and slow down of the flow due to increased roughness leads to high net deposition in the mussel bed. In addition, the ability of young mussels to quickly climb on top of deposited material results in rapid trapping of large amounts of fine sediment. In the wake of the mussel bed, deposition is also high because of reduced flow velocities. The effects of different existing mussel bed patterns were also evaluated. Patchiness and specifically striped patterns cause mussel beds to experience less sedimentation than uniformly covered beds of the same size and may therefore be favorable to mussels.

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Biophysical interactions between organisms and hydrodynamic forces are a main determinant of geomorphology of intertidal areas. Especially vascular plants have striking effects on intertidal geomorphology. Seagrasses and salt-marsh plants that inhabit intertidal areas are knownto have strongly contrasting morphologies. Differences in growth strategy by which plants cope with hydrodynamic forces are particularly interesting, as modification of these forces determine if and how species enhance sediment accretion. This raises the question to what extent differences in plant growth strategies directly affect the biogeomorphological development of the estuarine landscape. In this paper we i) provide a concise overview of our recent research on this topic, which has often been published in the more ecological literature, and ii) indicate how we have recently assessed the geomorphological effect of different vegetation types, by combining a series of unidirectional flow studies in flumes and hydrodynamic modeling at the landscape with a mechanistic hydrodynamic model (Delft-3D).@en