Meeting:Abstract 2011 CSDMS meeting-043
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A velocity-dependant friction law for flexible vegetation in a 2D hydrodynamic model.
[[Image:|300px|right|link=File:]]In the tidal flats of Robert Banks (British Columbia, Canada), large parts of the intertidal area are vegetated with eelgrass (Zostera Marina and Zostera Japonica). Such vegetation has an influence on the flow field and we aim at describing this effect in a 2D large-scale hydrodynamic model.
In a general case, vegetation causes an increase in the roughness that modifies the flow properties. For submerged vegetation, this roughness is related in particular to the height of the plants in the water. However, for very flexible plants such as eelgrass, the plant height is changing with the flow velocity since the plants are bending with the currents.
Existing studies concerning the effect of flexible vegetation on a flow are mostly focused on the small scale properties of the velocity and turbulence profiles. Such results can not be directly incorporated into 2D hydrodynamic models. On the other hand, 3D hydrodynamic modeling is still computationally demanding and is not appropriate for large-scale studies and engineering applications.
For that reason, we developed an integrated formulation of the effects of flexible vegetation on the flow, with the following approach: The roughness is represented through an equivalent Manning’s coefficient, which depends on both the water depth and the flow velocity.
Simulations are performed with the Telemac2d model, which has been modified to incorporate the velocity-dependant friction law. Preliminary results show that the proposed law is able to account for qualitative modifications in the tidal flow. In particular, the simulation provides a dissymmetric flow pattern, with ebb velocities slower than flood velocities, as observed in the field.
