Surf Zone Turbulence and Suspended Sediment Dynamics—A Review

Aagaard, Troels; Brinkkemper, Joost; Christensen, Drude F.; Hughes, Michael G.; Ruessink, Gerben

doi:10.3390/jmse9111300

Cited by 11 publications

(5 citation statements)

References 106 publications

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“…Note, however, that Rouse profiles are a very simplified analysis of mixing. They are based on many assumptions and the underlying processes of sediment suspension in surf zones under ocean waves are very complex, with complicating factors like grain size (e.g., Coleman, 1970), burst and sweep events (e.g., Soldati & Marchioli, 2012), horizontal non‐uniformities and advection (e.g., van der Zanden et al., 2017a) or intrawave turbulence (e.g., Aagaard et al., 2021) for example.…”

Section: Discussionmentioning

confidence: 99%

Near‐Bed Sediment Transport Processes During Onshore Bar Migration in Large‐Scale Experiments: Comparison With Offshore Bar Migration

et al. 2023

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Nearshore sand bars are alongshore ridges on the seabed, typically located in the shoaling and surf zones of many beaches around the world (e.g., Wijnberg & Kroon, 2002;Wright & Short, 1984). They can be alongshore uniform or feature complex geometries like rip channels and crescentic shapes (e.g., van Enckevort & Ruessink, 2003b). In regards to the predominant mechanism of their formation, the breakpoint hypothesis, originally proposed by Dyhr-Nielsen and Sørensen (1970) and demonstrated via numerical modeling by Dally and Dean (1984), is widely accepted. There, the bars form via convergence of onshore transport from bedload under shoaling waves and offshore transport from suspended transport under broken waves-thus being located close to the points of wave breaking. Through wave breaking bars promote energy dissipation. As a consequence, less wave energy reaches the shoreline, reducing erosion and storm damage. Additionally, bars play an important role

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Section: Discussionmentioning

confidence: 99%

Near‐Bed Sediment Transport Processes During Onshore Bar Migration in Large‐Scale Experiments: Comparison With Offshore Bar Migration

et al. 2023

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“…Related measurement problems originated from air bubbles which indicate increased levels of turbulence in the water column. As turbulence and sediment suspension are inherently linked, see Aagaard et al (2021) for example, this indicates that sediment suspension at 0 < x′ < 1.5 m was either similar or larger than further onshore (−0.5 < x′ < 0m)-which is supported by various studies that linked turbulence from wave breaking to increased sediment suspension (e.g., Yu et al, 1993or Zhou et al, 2017. Thus, one might expect current-related, suspended net offshore transport to stay constant or increase on the bar's onshore side (0 < x′ < 1.5 m).…”

Section: Transport Processes Onshore Of the Barmentioning

confidence: 99%

Near‐Bed Sediment Transport During Offshore Bar Migration in Large‐Scale Experiments

et al. 2022

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This study presents novel insights into hydrodynamics and sediment fluxes in large‐scale laboratory experiments with bichromatic wave groups on a relatively steep initial beach slope (1:15). An Acoustic Concentration and Velocity Profiler provided detailed information of velocity and sand concentration near the bed from shoaling up to the outer breaking zone including suspended sediment and sheet flow transport. The morphological evolution was characterized by offshore migration of the outer breaker bar. Decomposition of the total net transport revealed a balance of onshore‐directed, short wave‐related and offshore‐directed, current‐related net transport. The short wave‐related transport mainly occurred as bedload over small vertical extents. It was linked to characteristic intrawave sheet flow layer expansions during short wave crests. The current‐related transport rate featured lower maximum flux magnitudes but occurred over larger vertical extents. As a result, it was larger than the short wave‐related transport rate in all but one cross‐shore position, driving the bar’s offshore migration. Net flux magnitudes of the infragravity component were comparatively low but played a nonnegligible role for total net transport rate in certain cross‐shore positions. Net infragravity flux profiles sometimes featured opposing directions over the vertical. The fluxes were linked to a standing infragravity wave pattern and to the correlation of the short wave envelope, controlling suspension, with the infragravity wave velocity.

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“…The induced sediment suspension and transport is one of the most important resulting processes affected by depth-limited wave breaking (Aagaard et al. 2021). Wave skewness and asymmetry are well understood to affect sediment transport (e.g.…”

Section: Discussionmentioning

confidence: 99%

Cross-shore wind-induced changes to field-scale overturning wave shape

et al. 2023

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The shape of depth-limited breaking-wave overturns is important for turbulence injection, bubble entrainment and sediment suspension. Overturning wave shape depends on a nonlinearity parameter $H/h$ , where $H$ is the wave height, and $h$ is the water depth. Cross-shore wind direction (offshore/onshore) and magnitude affect laboratory shoaling wave shape and breakpoint location $X_{{bp}}$ , but wind effects on overturning wave shape are largely unstudied. We perform field-scale experiments at the Surf Ranch wave basin with fixed bathymetry and $\approx 2.25$ m shoaling solitons with small height variations propagating at $C=6.7\ \mathrm {m}\ \mathrm {s}^{-1}$ . Observed non-dimensional cross-wave wind $U_w$ was onshore and offshore, varying realistically ( $-1.2 < U_{w}/C < 0.7$ ). Georectified images, a wave staff, and lidar are used to estimate $X_{{bp}}$ , $H/h$ , overturn area $A$ and aspect ratio for 22 waves. The non-dimensionalized $X_{{bp}}$ was inversely related to $U_{w}/C$ . The non-dimensional overturn area and aspect ratio also were inversely related to $U_{w}/C$ , with smaller and narrower overturns for increasing onshore wind. No overturning shape dependence on the weakly varying $H/h$ was seen. The overturning shape variation was as large as prior laboratory experiments with strong $H/h$ variations without wind. An idealized potential air flow simulation on steep shoaling soliton shape has strong surface pressure variations, potentially inducing overturning shape changes. Through wave-overturning impacts on turbulence and sediment suspension, coastal wind variations could be relevant for near-shore morphology.

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Surf Zone Turbulence and Suspended Sediment Dynamics—A Review

Cited by 11 publications

References 106 publications

Near‐Bed Sediment Transport Processes During Onshore Bar Migration in Large‐Scale Experiments: Comparison With Offshore Bar Migration

Near‐Bed Sediment Transport Processes During Onshore Bar Migration in Large‐Scale Experiments: Comparison With Offshore Bar Migration

Near‐Bed Sediment Transport During Offshore Bar Migration in Large‐Scale Experiments

Cross-shore wind-induced changes to field-scale overturning wave shape

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