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Cross‐shore sand transport by infragravity waves as a function of beach steepness
Author(s) -
Bakker A. T. M.,
Brinkkemper J. A.,
Steen F.,
Tissier M. F. S.,
Ruessink B. G.
Publication year - 2016
Publication title -
journal of geophysical research: earth surface
Language(s) - English
Resource type - Journals
eISSN - 2169-9011
pISSN - 2169-9003
DOI - 10.1002/2016jf003878
Subject(s) - infragravity wave , geology , swell , surf zone , shore , submarine pipeline , swash , sediment transport , beach morphodynamics , seismology , geotechnical engineering , oceanography , geomorphology , sediment , wave propagation , physics , mechanical wave , longitudinal wave , quantum mechanics
Two field data sets of near‐bed velocity, pressure, and sediment concentration are analyzed to study the influence of infragravity waves on sand suspension and cross‐shore transport. On the moderately sloping Sand Motor beach (≈1:35), the local ratio of infragravity wave height to sea‐swell wave height is relatively small ( H IG / H SW <0.4), and sand fluxes are related to the correlation of the infragravity‐wave orbital motion with the sea‐swell wave envelope, r 0 . When the largest sea‐swell waves are present during negative infragravity velocities (bound wave, negative correlation r 0 ), most sand is suspended here, and the infragravity sand flux q IG is offshore. When r 0 is positive, the largest sea‐swell waves are present during positive infragravity velocities (free wave), and q IG is onshore directed. For both cases, the infragravity contribution to the total sand flux is, however, relatively small (<20%). In the inner surf zone of the gently (≈1:80) sloping Ameland beach, the infragravity waves are relatively large ( H IG / H SW >0.4), most sand is suspended during negative infragravity velocities, and q IG is offshore directed. The infragravity contribution to the total sand flux is considerably larger and reaches up to ≈60% during energetic conditions. On the whole, H IG / H SW is a good indicator for the infragravity‐related sand suspension mechanism and the resulting infragravity sand transport direction and relative importance.