TY - JOUR
T1 - Cross-shore sand transport by infragravity waves as a function of beach steepness
AU - de Bakker, A.T.M.
AU - Brinkkemper, J.A.
AU - Van der Steen, Florian
AU - Tissier, M.F.S.
AU - Ruessink, B.G.
PY - 2016
Y1 - 2016
N2 - 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 (HIG/HSW<0.4), and sand fluxes are related to the correlation of the infragravity-wave orbital motion with the sea-swell wave envelope, r0. When the largest sea-swell waves are present during negative infragravity velocities (bound wave, negative correlation r0), most sand is suspended here, and the infragravity sand flux qIG is offshore. When r0 is positive, the largest sea-swell waves are present during positive infragravity velocities (free wave), and qIG 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 (HIG/HSW>0.4), most sand is suspended during negative infragravity velocities, and qIG 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, HIG/HSW is a good indicator for the infragravity-related sand suspension mechanism and the resulting infragravity sand transport direction and relative importance.
AB - 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 (HIG/HSW<0.4), and sand fluxes are related to the correlation of the infragravity-wave orbital motion with the sea-swell wave envelope, r0. When the largest sea-swell waves are present during negative infragravity velocities (bound wave, negative correlation r0), most sand is suspended here, and the infragravity sand flux qIG is offshore. When r0 is positive, the largest sea-swell waves are present during positive infragravity velocities (free wave), and qIG 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 (HIG/HSW>0.4), most sand is suspended during negative infragravity velocities, and qIG 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, HIG/HSW is a good indicator for the infragravity-related sand suspension mechanism and the resulting infragravity sand transport direction and relative importance.
U2 - 10.1002/2016JF003878
DO - 10.1002/2016JF003878
M3 - Article
SN - 2169-9003
VL - 121
JO - Journal of geophysical research. Earth surface
JF - Journal of geophysical research. Earth surface
ER -