Longshore current and wave height modulation at tidal frequency inside the surf zone

Thornton, Edward B.; Kim, Chang S.

doi:10.1029/93jc01440

Cited by 45 publications

(35 citation statements)

References 9 publications

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“…List (1992) compared his 1D-model with data obtained at Duck, North Carolina to explain the release of bound long waves within the surfzone. Reniers et al (2002) used a linear 1D spectral model and measurementdata from the DELILAH field experiment (Thornton and Kim, 1993) and obtained favorable comparisons for the infragravity conditions. A subset of that data was utilized by Van Dongeren et al (2003) in a comparison with a 2D non-linear model that showed the beach at the time of the DELILAH experiment could be considered as being alongshore uniform for the infragravity conditions.…”

Section: Introductionmentioning

confidence: 99%

Modelling infragravity motions on a rip-channel beach

Reniers

MacMahan

Thornton

et al. 2006

Coastal Engineering

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Section: Introductionmentioning

confidence: 99%

Modelling infragravity motions on a rip-channel beach

Reniers

MacMahan

Thornton

et al. 2006

Coastal Engineering

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“…Where discrepancies occurred, these were shown to be related to the rate of dissipation of wave energy through breaking. Both the measured and modeled results were able to demonstrate the wellknown result [Thornton and Kim, 1993] that wave energy fluxes and dissipation rates depend strongly on tidal height. While corresponding ground-truth measurements of wave energy flux were not able to be made, the self:consistency of the bathymetry, radar measured energy fluxes, and model results argues strongly for their validity.…”

Section: Discussionmentioning

confidence: 53%

“…Incident wave energy is the primary driving mechanism for nearshore dynamics, and the dissipation of wave energy when waves break over offshore bars has a major influence on the amount of this energy that eventually reaches the shore. In particular, as shown by Thornton and Kim [1993], the variation in water depth over a bar throughout a tidal cycle will cause corresponding variations in dissipation which will, in turn, induce a strong tidal cycle modulation in wave energy flux inside the bar. These authors show that this modulation will then be transferred to processes such as longshore currents that are driven by wave energy.…”

Section: Introductionmentioning

confidence: 99%

S band Doppler radar measurements of bathymetry, wave energy fluxes, and dissipation across an offshore bar

McGregor¹,

Poulter²,

Smith³

1998

J. Geophys. Res.

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Abstract.The use of a shore-based microwave Doppler radar for the remote sensing of ocean wave propagation over an offshore sand bar was investigated. The radar yielded high spatial resolution measurements of several quantities of importance in the study of bar dynamics. The spatial variation in wave phase with distance along the radar beam direction was used to calculate bathymetry with sufficient accuracy and resolution to clearly reveal the presence of the bar and the tidal cycle variation of water depth. This real-time bathymetry enabled the calculation of ocean wave energy fluxes from the radar velocity data. These energy fluxes showed good agreement with predictions from a numerical wave propagation model, except in regions of significant wave breaking, where the discrepancy between measured and modeled fluxes was found to be closely related to the modeled wave dissipation rate.

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“…The cross-shore shape of the mean longshore current during DELILAH was characterized by a broad peak over the trough [Smith et al, 1993], which modulated both in size and location with the tide [Thornton and Kim, 1993].…”

Section: Effective Depth Profiles During Delilahmentioning

confidence: 99%

Bar‐trapped edge waves and longshore currents

Bryan¹,

Bowen²

1998

J. Geophys. Res.

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Abstract. Edge waves react to the presence of a mean longshore current as though the current was a change in bottom topography. In this way, the cross-shore shape of the edge wave can be amplified over the current, relative to the shoreline, in the same way as the edge wave shape can be amplified over bars. On a beach with both longshore currents and bars, the degree of edge wave amplification (or trapping) depends on the strength and location of the longshore current shear relative to the steepness of the bottom slope and also on the direction of edge wave propagation relative to the longshore current. Weak longshore current shear over well-developed bars does not significantly alter edge wave trapping over bars simply enhancing or reducing the existing bar trapping effect. Conversely, strong current shears over gentle topography can govern the existence and location of edge wave trapping, the extreme example being edge wave trapping on plane beaches where the amplification is entirely due to the existence of mean longshore currents. In reality the possibilities are restricted, since the shape of the longshore current profile is primarily determined by the pattern of incident wave breaking, which itself depends on the beach profile. The importance of realistic current shear relative to realistic bottom slope in determining edge wave shape is demonstrated using frequency-wavenumber spectra taken during the Duck Experiment on Low-Frequency and Incident-band Longshore and Across-shore Hydrodynamics (DELILAH) at Duck, North Carolina. These frequency-wavenumber spectra show a general dominance of edge waves traveling with the longshore current. In cases where the current shear is strong relative to the bottom slope, the location of edge wave trapping changes as the longshore current profile changes with the tide. When the bar was well defined, the longshore current shear was rarely strong enough to influence the existence or location of edge wave trapping, but could have a enhancing effect. While past work [i.e. Sch6nfeldt, 1995] has suggested that edge waves, trapped and amplified on longshore currents, may cause bars to form on plane beaches and bars to move on barred beaches, these observations suggest that under most conditions, edge wave trapping on longshore currents is a subtle effect, modulated by sea level changes, and is unlikely to produce significant morphological change unless the current is very strong.

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Longshore current and wave height modulation at tidal frequency inside the surf zone

Cited by 45 publications

References 9 publications

Modelling infragravity motions on a rip-channel beach

Modelling infragravity motions on a rip-channel beach

S band Doppler radar measurements of bathymetry, wave energy fluxes, and dissipation across an offshore bar

Bar‐trapped edge waves and longshore currents

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