Sand suspension, storage, advection, and settling in surf and swash zones

Kobayashi, Nobuhisa; Johnson, Bradley D.

doi:10.1029/2000jc000557

Cited by 65 publications

(60 citation statements)

References 46 publications

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“…Nielsen, 1986;Van Rijn, 2007). Parameterizations for wave breaking effects on sediment pick-up or reference concentration have been proposed, for instance by adding TKE to bed shear stress (Hsu and Liu, 2004;Okayasu et al, 2010), by directly relating C 0 to turbulence (Steetzel, 1993), or by relating pick-up or reference concentration to breaking wave characteristics (Mocke and Smith, 1992;Kobayashi and Johnson, 2001;Spielmann et al, 2004). However, none of these studies have led to a widely applied model for wave breaking effects on sediment pick-up, and the validation of these existing parameterizations against a wide range of surf zone suspension measurements seems a crucial next step in advancing suspended sand transport modeling.…”

Section: Discussionmentioning

confidence: 99%

“…Since breaking-generated turbulent kinetic energy may display a distinct intra-wave variation, especially under plunging waves, the suspension by wave breaking turbulence may drive a net wave-related suspended sediment flux (Yoon and Cox, 2012;Brinkkemper et al, 2017). Parameterizations have been developed to account for such wave breaking effects on sediment pick-up rates (Kobayashi and Johnson, 2001;Hsu and Liu, 2004;Spielmann et al, 2004) and net wave-related suspended sediment fluxes (Van Rijn, 2007). However, existing modeling approaches are generally not supported by a wide range of experimental observations.…”

Section: Introductionmentioning

confidence: 99%

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Suspended and Bedload Transport in the Surf Zone: Implications for Sand Transport Models

Zanden

O’Donoghue

et al. 2017

Int. Conf. Coastal. Eng.

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This paper presents results obtained during a large-scale wave flume experiment focused at measuring hydrodynamics and sediment transport processes in the wave breaking region. The experiment involved monochromatic plunging breaking waves over a mobile bed barred profile consisting of D 50 = 0.24 mm sand. Vertical profiles of velocity, turbulence, sand concentration and sand fluxes were measured at 12 cross-shore locations, covering the shoaling region up to the inner surf zone. Particularly high-resolution profiles were obtained near the bed within the wave bottom boundary layer, using an acoustic sediment concentration and velocity profiler (ACVP). Sheet flow concentration and particle velocities were measured at two locations near the bar crest using two conductivity-based concentration measurement tanks (CCM+). Total transport rates, obtained from the evolving bed profile measurements, were decomposed into suspended and bedload transport contributions across the bar. The present paper presents a summary of the key findings of the experiment, which are used to discuss existing approaches for modeling suspended and bed load transport in the surf zone.

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Section: Discussionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Suspended and Bedload Transport in the Surf Zone: Implications for Sand Transport Models

Zanden

O’Donoghue

et al. 2017

Int. Conf. Coastal. Eng.

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“…The volume of suspended sediment per unit area, V s , is computed as a simple empirical function of the dissipation as introduced in Kobayashi and Johnson (2001):…”

Section: Total Bedload Transportmentioning

confidence: 99%

Material Placement in the Nearshore: Laboratory and Numerical Model Investigation

Johnson¹,

Smith²

2012

Int. Conf. Coastal. Eng.

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Typical practice for a century has been to transport dredged sand to an offshore disposal site in deep water where the sediment is lost from the littoral system. The alternative of nearshore placement can retain the sand, but the fate of the material is poorly understood. A set of laboratory experiments were conducted, using tracer sand, with the intent of quantifying the migration of material with alternative dredged mound placements within the surf zone. Conventional depth-integrated tracer sand transport models can utilize a correction factor or a gradient diffusion mechanism to represent the effects of the depth variation. In the surf zone, however, an analytical correction factor is not available and a gradient diffusion coefficient is arbitrary with no physical basis. An alternative simple advective transport sand model is introduced herein that explicitly predicts both the advection associated with the return current and the wave-related onshore transport. With a simple framework based on a suspended layer and a bedload layer of arbitrary transport directions, the Taylor dispersion of tracer sand is explicitly computed without any dependence on a diffusion mechanism. Both the modeled and measured results indicate transport directed offshore by the undertow, onshore by the wave asymmetry, and down-drift as forced by the longshore current.

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“…However, because strong turbulent flow conditions in the surf zone enhance sediment suspension in the water column, the vertical distribution of the sediment concentration is influenced by wave breaking turbulence. There is a consensus that turbulence effects should be incorporated into cross-shore sediment transport modeling (e.g., [10][11][12][13][14][15]). …”

Section: Introductionmentioning

confidence: 99%

“…With the stirring effect, they demonstrated improved beach profile prediction by comparison of their results with laboratory data. Kobayashi and Johnson [11] developed a time-averaged cross-shore sediment transport model that includes a sediment suspension effect due to wave breaking turbulence. Butt et al [12] modified the energetic-type cross-shore sediment transport model by including turbulent kinetic energy (TKE) terms for the swash and inner surf zones.…”

Section: Introductionmentioning

confidence: 99%

Parameterization of Time-Averaged Suspended Sediment Concentration in the Nearshore

Yoon

Cox

Mori

2015

Water

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Abstract:To quantify the effect of wave breaking turbulence on sediment transport in the nearshore, the vertical distribution of time-averaged suspended sediment concentration (SSC) in the surf zone was parameterized in terms of the turbulent kinetic energy (TKE) at different cross-shore locations, including the bar crest, bar trough, and inner surf zone. Using data from a large-scale laboratory experiment, a simple relationship was developed between the time-averaged SSC and the time-averaged TKE. The vertical variation of the time-averaged SSC was fitted to an equation analogous to the turbulent dissipation rate term. At the bar crest, the proposed equation was slightly modified to incorporate the effect of near-bed sediment processes and yielded reasonable agreement. This parameterization yielded the best agreement at the bar trough, with a coefficient of determination R 2 ≥ 0.72 above the bottom boundary layer. The time-averaged SSC in the inner surf zone showed good agreement near the bed but poor agreement near the water surface, suggesting that there is a different sedimentation mechanism that controls the SSC in the inner surf zone.

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Sand suspension, storage, advection, and settling in surf and swash zones

Cited by 65 publications

References 46 publications

Suspended and Bedload Transport in the Surf Zone: Implications for Sand Transport Models

Suspended and Bedload Transport in the Surf Zone: Implications for Sand Transport Models

Material Placement in the Nearshore: Laboratory and Numerical Model Investigation

Parameterization of Time-Averaged Suspended Sediment Concentration in the Nearshore

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