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POSIDONIA - 2008

Wave Propagation over Posidonia oceanica: transmission, dissipation and vegetation/sediment hydrodynamics
Summary:

Posidonia oceanica, the most abundant seagrass species in the Mediterranean is a plant which has a fundamental role in the coastal sand budget and in protecting the shoreline from erosion. 
No large scale experiments had been conducted.

The objectives and scientific aims of the project are described below:
 
  • Measurement of wave attenuation, transmission and energy dissipation over Posidonia oceanica during low and high energy events in intermediate and shallow waters
  • Investigation in the effects of submergence ratio hs/D (hs=height of seagrass, D=water depth) and seagrass density (number of shoots per squared meter) on the above characteristics
  • Measurement of mean velocities above and within the seagrass and estimation of wave induced flow within the seagrass which influences processes such as nutrient uptake, waste removal and larval dispersion.
  • Measurement of bed friction and the associated damping due to the seagrass which is associated with sediment deposition and re-suspension.
  • Investigation in the effect of Posidonia oceanica on sand deposition and suspension by measuring suspended sand concentration and video recording the threshold of suspension within the canopy.
     
To provide experimental data for validation of numerical models on wave propagation over vegetation fields and to contribute to the formulation of parametric models, accounting for Posidonia oceanica effects, which are used in wave propagation, nearshore circulation and morphodynamic models.

The experiments, in prototype conditions(1:1 scale), have been conducted in the CIEM wave flume in Barcelona, using a 10.7m long meadow of artificial polypropylene plants, simulating Posidonia oceanica.