Energy Transfers and Reflection of Infragravity Waves at a Dissipative Beach Under Storm Waves

This study presents unpublished field observations of infragravity waves, collected at the dissipative beach of Saint‐Trojan (Oléron Island, France) during the storm Kurt (3 February 2017), characterized by incident short waves of significant heights reaching 9.5 m and peak periods reaching 22 s. Da...

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Bibliographic Details
Published in:Journal of geophysical research. Oceans 2020-05, Vol.125 (5), p.n/a
Main Authors: Bertin, Xavier, Martins, Kévin, Bakker, Anouk, Chataigner, Teddy, Guérin, Thomas, Coulombier, Thibault, Viron, Olivier
Format: Article
Language:English
Subjects:
Beach profiles
Beaches
bound wave
Coefficients
Data analysis
dissipative beach
Earth Sciences
Energy
Free surfaces
Geophysics
High tide
infragravity waves
Low tide
Mathematical models
merging
Modelling
numerical model
Oceanography
Peak periods
Phase lag
Reflection
Sciences of the Universe
Spectral analysis
Spectrum analysis
Storm waves
Storms
Surf zone
Variance analysis
Wave propagation
Wave reflection
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Summary:This study presents unpublished field observations of infragravity waves, collected at the dissipative beach of Saint‐Trojan (Oléron Island, France) during the storm Kurt (3 February 2017), characterized by incident short waves of significant heights reaching 9.5 m and peak periods reaching 22 s. Data analysis reveals the development of exceptionally large infragravity waves, with significant heights reaching 1.85 m close to shore. Field observations are complemented by numerical modeling with XBeach, which well reproduces the development of such infragravity waves. Model results reveal that infragravity waves were generated mainly through the bound wave mechanism, enhanced by the development of a phase lag with the shortwave energy envelope. Spectral analysis of the free surface elevation shows the generation of superharmonic and subharmonic infragravity waves, the latter dominating the free surface elevation variance close to shore. Modeling results suggest that subharmonic infragravity waves result, at least partly, from infragravity‐wave merging, promoted by the combination of free and bound infragravity waves propagating across a several kilometer‐wide surf zone. Due to the steeper slope of the upper part of the beach profile, observed and modeled reflection coefficients under moderate‐energy show a strong tidal modulation, with a weak reflection at low tide (R2
ISSN:2169-9275
2169-9291
DOI:10.1029/2019JC015714