Infragravity wave contribution to surf zone sediment transport — The role of advection

Aagaard, Troels; Greenwood, Brian

doi:10.1016/j.margeo.2008.01.017

Cited by 51 publications

(31 citation statements)

References 43 publications

(55 reference statements)

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“…Local suspended sediment transport measurements in field conditions tend to support this model (Aagaard and Greenwood, 2008;Osborne and Greenwood, 1992). Inside the surf zone, no clear model exists, but long wave transport tends to be predominantly landward.…”

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confidence: 94%

“…However, the relative importance of long waves has been showed to increase within the surf zone, as short wave dissipation occurs via wave breaking, and has been reported to dominate the suspended sediment transport in the inner surf zone (Aagaard and Greenwood, 2008).…”

Section: -Introductionmentioning

confidence: 99%

Section: -Introductionmentioning

confidence: 99%

“…Bauer and Greenwood (1990) and Aagaard and Greenwood (1994) have shown experimental evidence of such a mechanism. However drift velocities in the bottom boundary layer beneath standing waves are generally assumed to be small compared to lf and hf wave orbital motions and mean currents (Aagaard and Greenwood, 2008).Moreover, because of the feedback between the morphology and the long wave hydrodynamics, it is possible that existing morphologic features (bars) force the long-wave structure rather than the other way around as proposed by Symonds and Bowen (1984). It is complicated in field conditions to establish a relationship between morphology and long-6 wave pattern without comparing the same situation with and without long waves or with and without the initial forcing morphology.…”

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confidence: 99%

“…Inside the surf zone, no clear model exists, but long wave transport tends to be predominantly landward. Aagaard and Greenwood (2008) proposed that long waves advect sediment away from maxima in the relative incident wave height (H/h), which typically occur near the crests of longshore bars, implying a divergence of lf induced sediment transport at wave breakpoints (bars), which should cause destruction of the bar crest or the landward migration of the bar crest.There are evidences of the importance of lf motions in beach profile morphology but there is7 not yet a clear picture of the nature of this influence in terms of magnitude of sediment transport rates and direction. Coastal profile models based on a dominance of mean return flow and wave asymmetry are capable of good predictions of the cross-shore bar migration when properly calibrated while the inner surf zone morphological evolution is not as well predicted (Dubarbier et al, 2015).…”

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confidence: 99%

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Sediment transport and beach profile evolution induced by bi-chromatic wave groups with different group periods

Alsina

Padilla

Caceres

2016

Coastal Engineering

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In this paper, large-scale experimental data are presented showing the beach profile morphological evolution induced by four different bi-chromatic wave conditions characterized by very similar energy content between them but varying the modulation period. Important differences were observed in the resultant beach profiles as a function of the wave group periods. Larger variability in the profile evolution is generally observed for larger wave group periods and, more importantly, as the wave group period increases the distance between the generated breaker bar and the shoreline increases. The measured primary wave height to depth ratio () increases with the wave group period, which is consistent with the observed larger wave height at the breaking location. The primary wave 2 breaking location is also observed at increasing distances with respect to the initial shoreline as the wave group period increases. The variation in  with wave group period is related to the selective energy dissipation of the higher primary frequency component (f1) during the wave group shoaling. Broad bandwith conditions (reduced wave group period) lead to larger dissipation of wave heights at the f1 component relative to f2 resulting in a reduction in the wave modulation and primary wave height at the breaking location. Suspended sediment fluxes obtained from collocated velocity and sediment concentration measurements in the surf zone showed a consistently larger contribution of the mean return flow to the suspended sediment fluxes compared with the wave group and primary wave components. The distinct beach profile evolution in terms of bar location is interpreted from an increasing distance of the mean breakpoint location and the location of maximum return flow with respect to the shoreline as the wave group period increases.Keywords: bi-chromatic wave groups, bar morphology, sediment transport, suspended sediment concentration, large scale experiments, morphodynamics. -IntroductionHigh frequency (hf) wave groups and the associated low frequency (lf) waves are natural characteristics of random waves propagating to coastal areas. Wave grouping has important implications in coastal sediment transport and in the evolution of the coastal morphology.Measured sediment transport rates in surf zone conditions suggest a larger influence of mean components and short-scale wind and swell waves in the net cross-shore sediment transport (Ruessink et al., 1998). However, the relative importance of long waves has been showed to increase within the surf zone, as short wave dissipation occurs via wave breaking, and has 3 been reported to dominate the suspended sediment transport in the inner surf zone (Aagaard and Greenwood, 2008).Moreover, beach evolution is the result of sediment transport gradients that may vary at the time-scales of long waves and wave groups. Wave groups also introduce further intermittency into the short-wave scale hydrodynamics (i.e. wave breaking, slow modulation of the water depth and wave height to water depth ratio...

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mentioning

confidence: 94%

Section: -Introductionmentioning

confidence: 99%

Section: -Introductionmentioning

confidence: 99%

mentioning

confidence: 99%

mentioning

confidence: 99%

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Sediment transport and beach profile evolution induced by bi-chromatic wave groups with different group periods

Alsina

Padilla

Caceres

2016

Coastal Engineering

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Source regions and reflection of infragravity waves offshore of the U.S.s Pacific Northwest

2015

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Infragravity waves are oceanic surface gravity waves but with wavelengths (tens of km) and periods (>30 s) much longer than wind waves and swell. Mostly studied in shallow water, knowledge of infragravity waves in deep water has remained limited. Recent interest in deep water infragravity waves has been motivated by the error they may contribute to future high‐resolution satellite radar altimetry measurements of sea level. Here deep water infragravity waves offshore of the Pacific Northwest of the U.S. were studied using differential pressure gauges which were deployed as part of the Cascadia Initiative array from September 2012 to May 2013. Cross correlation of the records revealed direction of infragravity wave propagation across the array, from which source regions were inferred. The dominant source was found to be the coastline to the east, associated with large wind waves and swell incident on the eastern side of the basin. The source shifted southward during northern‐hemisphere summer, and on several days in the record infragravity waves arrived from the western side of the Pacific. Asymmetry of cross‐correlation functions for five of these westerly arrivals was used to calculate the ratio of seaward to shoreward propagating energy, and hence estimate the strength of infragravity wave reflection at periods of 100–200 s. Reflection of these remote arrivals from the west appeared to be strong, with a lower bound estimate of r = 0.49 ± 0.29 (reflection coefficient ± standard error) and an upper bound estimate of r = 0.74 ± 0.06. These results suggest that reflection at ocean boundaries may be an important consideration for infragravity waves in the deep ocean.

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Cross-shore sand transport by infragravity waves as a function of beach steepness

Bakker

Brinkkemper

Steen

et al. 2016

J. Geophys. Res. Earth Surf.

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Two field data sets of near‐bed velocity, pressure, and sediment concentration are analyzed to study the influence of infragravity waves on sand suspension and cross‐shore transport. On the moderately sloping Sand Motor beach (≈1:35), the local ratio of infragravity wave height to sea‐swell wave height is relatively small (HIG/HSW<0.4), and sand fluxes are related to the correlation of the infragravity‐wave orbital motion with the sea‐swell wave envelope, r0. When the largest sea‐swell waves are present during negative infragravity velocities (bound wave, negative correlation r0), most sand is suspended here, and the infragravity sand flux qIG is offshore. When r0 is positive, the largest sea‐swell waves are present during positive infragravity velocities (free wave), and qIG is onshore directed. For both cases, the infragravity contribution to the total sand flux is, however, relatively small (<20%). In the inner surf zone of the gently (≈1:80) sloping Ameland beach, the infragravity waves are relatively large (HIG/HSW>0.4), most sand is suspended during negative infragravity velocities, and qIG is offshore directed. The infragravity contribution to the total sand flux is considerably larger and reaches up to ≈60% during energetic conditions. On the whole, HIG/HSW is a good indicator for the infragravity‐related sand suspension mechanism and the resulting infragravity sand transport direction and relative importance.

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Infragravity wave contribution to surf zone sediment transport — The role of advection

Cited by 51 publications

References 43 publications

Sediment transport and beach profile evolution induced by bi-chromatic wave groups with different group periods

Sediment transport and beach profile evolution induced by bi-chromatic wave groups with different group periods

Source regions and reflection of infragravity waves offshore of the U.S.s Pacific Northwest

Cross-shore sand transport by infragravity waves as a function of beach steepness

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