Morphodynamic modeling of an embayed beach under wave group forcing

Reniers, Ad; Roelvink, Dano; Thornton, Edward B.

doi:10.1029/2002jc001586

Cited by 250 publications

(286 citation statements)

References 51 publications

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“…This short wave averaged, long wave approach was found capable to resolve the mean surfzone flow as well as the low frequency flow associated with low frequency (infragravity) waves and VLF motions (Reniers et al, , 2007. A complete model description and laboratory validation is given in Reniers et al (2004) and model settings are similar to the settings used therein, unless stated otherwise.…”

Section: Numerical Model Simulationsmentioning

confidence: 99%

Vortical VLF Motions Under Shore-Normal Incident Waves

Schipper

Reniers

MacMahan

et al. 2012

Int. Conf. Coastal. Eng.

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Field observations and numerical model simulations are examined to investigate the magnitude of vortical very low frequency (VLF) velocity fluctuations (i.e. large scale surfzone eddies) under different offshore wave forcing. Observations of vortical VLF motions under shore -normal wave incidence at Duck, NC, USA are re-analyzed and compared with the characteristics of the incident wave spectrum. Long wave periods and narrow frequency spread incident waves were found to coincide with stronger vortical VLF motions. Numerical model simulations investigating the effect of the incident wave parameters in a more isolated way confirm the observed effect of frequency spread and wave period on the magnitude of VLF motions. Variations in incident wave spectrum resulted in changes in the vortical VLF magnitude of the same order as the magnitude of the vortical VLF velocity fluctuations themselves. These results imply that under shore-normal incident waves strong vortical VLF velocity fluctuations in the surfzone are more likely under swell conditions and at swell dominated coasts.

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Section: Numerical Model Simulationsmentioning

confidence: 99%

Vortical VLF Motions Under Shore-Normal Incident Waves

Schipper

Reniers

MacMahan

et al. 2012

Int. Conf. Coastal. Eng.

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“…However, the corresponding situation in the surf zone is much more complex because of the presence of the breaking waves leading to the so-called 'bedsurf' coupling, namely, the coupling between the growing bed features and the wave field. Thus, in the existing models (Damgaard et al 2002;Caballeria et al 2002;Fachin & Sancho 2004;Reniers et al 2004) the saturation of the growth of bars either has not been reached or has not been discussed. Therefore, the finite-amplitude dynamics of surf zone transverse/oblique bars in the case of shore-oblique wave incidence remains largely unexplored.…”

Section: Introductionmentioning

confidence: 99%

“…The more traditional method considers the basic physical principles (momentum, water mass, sediment conservation) as partial differential equations, then discretizes them either by finite differences or by spectral methods and finally solves them. This method has been applied to the formation of crescentic bars by Damgaard et al (2002) and by Reniers, Roelvink & Thornton (2004) in case of shore-normal wave incidence. In a similar context and with a similar method, Caballeria et al (2002) examined the finite-amplitude dynamics of both crescentic and transverse bars.…”

Section: Introductionmentioning

confidence: 99%

Generation and nonlinear evolution of shore-oblique/transverse sand bars

et al. 2006

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The coupling between topography, waves and currents in the surf zone may selforganize to produce the formation of shore-transverse or shore-oblique sand bars on an otherwise alongshore uniform beach. In the absence of shore-parallel bars, this has been shown by previous studies of linear stability analysis, but is now extended to the finite-amplitude regime. To this end, a nonlinear model coupling wave transformation and breaking, a shallow-water equations solver, sediment transport and bed updating is developed. The sediment flux consists of a stirring factor multiplied by the depthaveraged current plus a downslope correction. It is found that the cross-shore profile of the ratio of stirring factor to water depth together with the wave incidence angle primarily determine the shape and the type of bars, either transverse or oblique to the shore. In the latter case, they can open an acute angle against the current (upcurrent oriented) or with the current (down-current oriented). At the initial stages of development, both the intensity of the instability which is responsible for the formation of the bars and the damping due to downslope transport grow at a similar rate with bar amplitude, the former being somewhat stronger. As bars keep on growing, their finite-amplitude shape either enhances downslope transport or weakens the instability mechanism so that an equilibrium between both opposing tendencies occurs, leading to a final saturated amplitude. The overall shape of the saturated bars in plan view is similar to that of the small-amplitude ones. However, the final spacings may be up to a factor of 2 larger and final celerities can also be about a factor of 2 smaller or larger. In the case of alongshore migrating bars, the asymmetry of the longshore sections, the lee being steeper than the stoss, is well reproduced. Complex dynamics with merging and splitting of individual bars sometimes occur. Finally, in the case of shore-normal incidence the rip currents in the troughs between the bars are jet-like while the onshore return flow is wider and weaker as is observed in nature.

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“…We follow (Roelvink and Stive 1989) and (Reniers et al 2004), who assumed that this extra u rol was proportional to the dissipation of roller energy, i.e.,…”

Section: Bed Evolution and Sediment Transportmentioning

confidence: 99%

“…The depth-averaged roller energy balance is an extension of the one proposed by Reniers et al (2004), which we have adapted to account for wave-current interactions,…”

Section: Hydrodynamic Equationsmentioning

confidence: 99%

Observations and modeling of surf zone transverse finger bars at the Gold Coast, Australia

et al. 2014

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The occurrence and characteristics of transverse finger bars at Surfers Paradise (Gold Coast, Australia) have been quantified with 4 years of time-exposure video images. These bars are attached to the inner terrace and have an oblique orientation with respect to the coastline. They are observed during 24 % of the study period, in patches up to 15 bars, with an average lifetime of 5 days and a mean wavelength of 32 m. The bars are observed during obliquely incident waves of intermediate heights. Bar crests typically point toward the incoming wave direction, i.e., they are upcurrent oriented. The most frequent beach state when bars are present (43 % of the time) is a rhythmic low-tide terrace and an undulating outer bar. A morphodynamic model, which describes the feedback between waves, currents, and bed evolution, has been applied to study the mechanisms for finger bar formation. Realistic positive feedback leading to the formation of the observed bars only occurs if the sediment resuspension due to roller-induced turbulence is included. This causes the depth-averaged sediment concentration to decrease in the seaward direction, enhancing the convergence of sediment transport in the offshore-directed flow perturbations that occur over the up-current bars. The longshore current strength also plays an important role; the offshore root-mean-square wave height and angle must be larger than some critical values (0.5 m and 20 • , respectively, at 18-m depth). Model-data comparison indicates that the modeled bar shape characteristics (up-current orientation) and the wave conditions leading to the bar formation agree with data, while the modeled wavelengths and migration rates are larger than the observed ones. The discrepancies might be because in the model we neglect the influence of the large-scale beach configuration.

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Morphodynamic modeling of an embayed beach under wave group forcing

Cited by 250 publications

References 51 publications

Vortical VLF Motions Under Shore-Normal Incident Waves

Vortical VLF Motions Under Shore-Normal Incident Waves

Generation and nonlinear evolution of shore-oblique/transverse sand bars

Observations and modeling of surf zone transverse finger bars at the Gold Coast, Australia

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