Bed level fluctuations in the inner surf and swash zone of a dissipative beach

Puleo, Jack A.; Lanckriet, Thijs; Blenkinsopp, Chris

doi:10.1016/j.margeo.2014.01.006

Cited by 37 publications

(56 citation statements)

References 45 publications

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“…In 1996 Perranporth was chosen as the site for the UK's first ARGUS video station (Davidson et al, 1997;Holman and Stanley, 2007) and these cameras remain operational to the present day. A series of swash experiments using arrays of in-situ instrumentation have been carried out on the high tide beach (Butt and Russell, 1999;Butt et al, 2001Butt et al, , 2002Butt et al, , 2007Masselink et al, 2005;Masselink and Russell, 2006;Lanckriet et al, 2014;Puleo et al, 2014a, b). Since 2010, the site has also become a focus for studies on rip currents (Austin et al, 2010Scott et al, 2014), their links to bather safety and their influence on bedform dynamics (Thorpe et al, 2013).…”

Section: Description Of Study Areamentioning

confidence: 99%

Role of wave forcing, storms and NAO in outer bar dynamics on a high-energy, macro-tidal beach

et al. 2014

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Outer sand bar dynamics on a high-energy macro-tidal beach were investigated using long-term (multi-year) field datasets of intertidal morphology and offshore bathymetry. Utilising a 15-year time-series of Argus video images, five distinct outer bar types were identified: Mega Rip, Longshore, Crescentic, Crescentic Attached and Welded. The most common classification was Crescentic Attached, with the outer bar oscillations being out of phase with the inner bar oscillations, as would be expected for the shore-normal wave approach at this site. The outer bar had a typical amplitude of 0.5-1 m and a longshore wavelength of 600 m. Changes in outer bar morphology were related to measured and modelled nearshore wave data. However, the outer bar morphology changed over a much longer time scale (monthly-to-annual) than the daily-to-weekly variations in wave height and period. An extended duration of energetic wave action was required to bring about an upstate bar transition to the Longshore or Mega Rip state, where the bar then remained arrested for a significant amount of time, requiring several months of low wave conditions to induce a down state transition through Crescentic to Welded. This slow morphological response is explained by extended relaxation times attributed to the large tidal range at the study site where the outer bar morphology is only active for part of the tidal cycle (several hours around low tide). The configuration and position of the outer bar were related: the more upstate (downstate) bar types being associated with a more offshore (onshore) bar position. The detrended outer bar position was significantly related to a forcing term based on wave power and disequilibrium of the dimensionless fall velocity with offshore (onshore) bar migration occurring when wave conditions were more (less) energetic that the antecedent conditions. The upstate end member (Longshore or Mega Rip) was attained sometime during the winter months for 14 out of the 16 years of monitoring; the outer bar remained attached to the low tide shoreline over the winter 2005/2006 and 2010/2011. These two winters with incomplete upstate cycles were characterised by the lowest winter wave conditions and negative winter North Atlantic Oscillation (NAO) indices, suggesting that the winter NAO is correlated with both beach state and nearshore bar configuration. KEYWORDS

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Section: Description Of Study Areamentioning

confidence: 99%

Role of wave forcing, storms and NAO in outer bar dynamics on a high-energy, macro-tidal beach

et al. 2014

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“…In terms of bed level measurements, only few instruments are able to sample the bed during both submerged and exposed state (see Puleo et al, 2014, for an overview). The aforementioned CCP seems to be the only instrument with sufficient accuracy (1 mm) and temporal resolution (sampling > 1 Hz) to study the intra-wave bed evolution in detail.…”

Section: Introductionmentioning

confidence: 99%

Bed level motions and sheet flow processes in the swash zone: Observations with a new conductivity-based concentration measuring technique (CCM + )

Zanden

Alsina

Caceres

et al. 2015

Coastal Engineering

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“…Previous studies have investigated the mean and turbulent flow field during the different phases of an individual swash cycle under natural [Puleo et al, 2000;Butt et al, 2004;Aagaard and Hughes, 2006;Raubenheimer et al, 2004;Blenkinsopp et al, 2011;Puleo et al, 2014b;Lanckriet et al, 2014] and laboratory [Cowen et al, 2003;Barnes et al, 2009;O'Donoghue et al, 2010;Sou et al, 2010;Sou and Yeh, 2011;Kikkert et al, 2012Kikkert et al, , 2013 conditions. Moreover, recent numerical studies [e.g., Brocchini and Baldock, 2008;Bakhtyar et al, 2009;Zhu and Dodd, 2013;Torres-Freyermuth et al, 2013] have provided additional information on the dynamics in this region, as they allow improved understanding of temporal and spatial variability of flow properties under different boundary/forcing conditions.…”

Section: Introductionmentioning

confidence: 99%

On the role of infiltration and exfiltration in swash zone boundary layer dynamics

et al. 2015

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Boundary layer dynamics are investigated using a 2‐D numerical model that solves the Volume‐Averaged Reynolds‐Averaged Navier‐Stokes equations, with a VOF‐tracking scheme and a k ‐ ϵ turbulence closure. The model is validated with highly resolved data of dam break driven swash flows over gravel impermeable and permeable beds. The spatial gradients of the velocity, bed shear stress, and turbulence intensity terms are investigated with reference to bottom boundary layer (BL) dynamics. Numerical results show that the mean vorticity responds to flow divergence/convergence at the surface that result from accelerating/decelerating portions of the flow, bed shear stress, and sinking/injection of turbulence due to infiltration/exfiltration. Hence, the zero up‐crossing of the vorticity is employed as a proxy of the BL thickness inside the shallow swash zone flows. During the uprush phase, the BL develops almost instantaneously with bore arrival and fluctuates below the surface due to flow instabilities and related horizontal straining. In contrast, during the backwash phase, the BL grows quasi‐linearly with less influence of surface‐induced forces. However, the infiltration produces a reduction of the maximum excursion and duration of the swash event. These effects have important implications for the BL development. The numerical results suggest that the BL growth rate deviates rapidly from a quasi‐linear trend if the infiltration is dominant during the initial backwash phase and the flat plate boundary layer theory may no longer be applicable under these conditions.

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Bed level fluctuations in the inner surf and swash zone of a dissipative beach

Cited by 37 publications

References 45 publications

Role of wave forcing, storms and NAO in outer bar dynamics on a high-energy, macro-tidal beach

Role of wave forcing, storms and NAO in outer bar dynamics on a high-energy, macro-tidal beach

Bed level motions and sheet flow processes in the swash zone: Observations with a new conductivity-based concentration measuring technique (CCM + )

On the role of infiltration and exfiltration in swash zone boundary layer dynamics

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