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You are here : eLibrary : IAHR World Congress Proceedings : 36th Congress - The Hague (2015) ALL CONTENT : Hydro-environment : Do surrogates tell the true story? Ęc a comparison of wave attenuation for natural and artificial se...
Do surrogates tell the true story? Ęc a comparison of wave attenuation for natural and artificial seagrass
Author : MAIKE PAUL(1) & LUCY GWEN GILLIS(2)
ABSTRACT
The interaction of flexible vegetation with hydrodynamics has been recognised to alter hydrodynamic forcing. To unravel
the influence of specific vegetation parameters on hydrodynamic forcing, artificial structures have been used that
represent their natural equivalents. Studies with surrogates provide insight in underlying processes, but remain a
simplification of natural conditions. It is therefore difficult to assess how well knowledge obtained with surrogates can be
transferred to living equivalents. This study provides a comparison of the temperate seagrass Zostera noltii with three
surrogates that have been used to mimic seagrass in flume experiments. It focuses on the wave attenuation capacity of
this species which is important from an eco-engineering perspective, but also incorporated the effect of an underlying flow.
A range of shoot densities and underlying flow velocities were applied to cover a wide range of natural conditions. Results
suggest that that the interaction of waves and flow dominates wave evolution even in the presence of relatively high
densities of Zostera noltii. But in the absence of flow, wave attenuation is strongly dependent on above ground biomass
for natural as well as artificial seagrass. For the given shoot densities, none of the used surrogates match the data
obtained for natural Zostera noltii. This could be attributed to the difference in leaf length as the natural leaves were almost
half the length of the shortest surrogates and hence the surrogates may have caused a higher blockage, resulting in a
higher increase of wave height. It may also be possible, that none of the surrogates is a suitable representation of Zostera
noltii under wave forcing, even though the flexible one appeared to behave comparably under flow. In that case, similarity
may not be transferrable between unidirectional and oscillatory hydrodynamic forcing and other parameters have to be
used to produce surrogates which yield the same wave attenuation as natural seagrass.
File Size : 376,823 bytes
File Type : Adobe Acrobat Document
Chapter : IAHR World Congress Proceedings
Category : 36th Congress - The Hague (2015) ALL CONTENT
Article : Hydro-environment
Date Published : 28/08/2015
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