Observations of large infragravity wave runup at Banneg Island, France

• Published in: Geophysical research letters 2014-02, Vol.41 (3), p.976-982
• Main Authors: Sheremet, Alex, Staples, Tracy, Ardhuin, Fabrice, Suanez, Serge, Fichaut, Bernard
• Format: Article
• Language: English
• Subjects: Astronomical instruments; Astronomical tides; Atmospheric and Oceanic Physics; Bands; Computational fluid dynamics; Computer simulation; Earth Sciences; Geodetics; Geomorphology; Geophysics; Gravity; Hydrodynamics; Identification; infragravity waves; Islands; Mathematical models; Nonlinearity; Numerical simulations; Physics; S waves; Sciences of the Universe; Shoaling; storm waves; Storms; Swell; Tides; trapped waves; Water; Water levels; Wave runup
• ISSN: 0094-8276; 1944-8007
• DOI: 10.1002/2013GL058880

On Banneg Island, France, very high water‐level events (6.5 m above the astronomical tide) have been observed on the western cliff, exposed to large swells from the North Atlantic. The analysis of hydrodynamic measurements collected during the storm of 10 February 2009 shows unusually high (over 2 m) infragravity wave runup events. By comparing runup observations to measurements in approximately 7 m of water and numerical simulations with a simplified nonlinear model, two distinct infragravity bands may be identified: an 80 s infragravity wave, produced by nonlinear shoaling of the storm swell; and a 300 s wave, trapped on the intertidal platform of the island and generating intermittent, low‐frequency inundation. Our analysis shows that the 300 s waves are a key component of the extreme water levels recorded on the island. Key Points The main component of 2 m infragravity wave at Banneg is a 300 s trapped wave