An Empirical Energetics-based Formulation for the Cross-shore Suspended Sediment Transport by Bound Infragravity Waves

Abstract

An energetics-based expression for the depth-averaged cross-shore suspended sediment transport rate due to infragravity (frequencies 0.004-0.04 Hz) waves is proposed by parameterizing moments of the near-bed flow. The moments represent the sediment stirring by short (frequencies 0.04-0.33 Hz) waves and the subsequent transport by the cross-shore motion of the infragravity waves phase-coupled to the incident groups. The data were gathered at three positions in 3- to 9-m depth in the multiple-bar system of Terschelling (Netherlands). In these depths bound infragravity waves are the sole contributors to the infragravity-induced sediment transport, causing it to be offshore directed. The parameterization is formulated in terms of the local Ursell number Ur and is valid for Ur ≤ 2.5; in addition, it contains spatial breaking information to account for the observed reduction in the moments by the breaking-induced destruction of the incident wave groups. The proposed expression was successfully cross-validated against two other data sets.