Modes of onshore sandbar migration at a single-barred and swell-dominated beach

Vidal-Ruiz, Jesús Adrián; Alegría-Arzaburu, Amaia Ruíz de

doi:10.1016/j.margeo.2020.106222

Cited by 10 publications

(4 citation statements)

References 25 publications

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“…According to the classification of onshore sandbar migration modes by Vidal‐Ruiz and Ruiz de Alegría‐Arzaburu (2019, 2020), the cases used in this study can be generally classified as mode I (section 2.4). The other identified modes (modes II–IV) consist of compounds of onshore and offshore sandbar migrations.…”

Section: Discussionmentioning

confidence: 99%

“…Figure 2 summarizes event duration, wave climate, and the observed onshore displacement of the cases used in the study. The cumulative energy flux for each event was calculated according to Vidal‐Ruiz and Ruiz de Alegría‐Arzaburu (2020). The tidal signal at Duck, NC is semidiurnal with an amplitude of 0.5 m (Figure 3d).…”

Section: Theory and Methodologymentioning

confidence: 99%

“…Using long‐term measurements, Vidal‐Ruiz and Ruiz de Alegría‐Arzaburu (2019, 2020) identified different modes of onshore sandbar migrations (modes I–IV) based on the cumulative wave energy and sandbar morphometric properties. The onshore sandbar migration cases used in the current study can be generally classified under mode I, where the sandbar is moving onshore under low‐energetic conditions (< 50 kW m −1 ) and subsequently weld with the shoreline.…”

Section: Theory and Methodologymentioning

confidence: 99%

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On the predictive skill of morphodynamic models for onshore sandbar migration

Hewageegana

Canestrelli

2021

Earth Surf Processes Landf

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A simplified process‐based approach for evaluating onshore sandbar migration is presented in this study. This approach takes wave‐averaged parameters as input and computes sediment transport processes using a reconstructed intra‐wave orbital velocity signal. The proposed method guarantees good predictive skills for multiple onshore sandbar migration cases without an ad hoc calibration for each scenario. The study differs from previous onshore sandbar migration models, where calibration and testing are performed on just one or few events, and model assessment for uncalibrated realizations is rarely carried out. The present version of the model only addresses onshore sandbar migrations. For the onshore migration cases analyzed, the model has better predictive skills than state‐of‐the‐art morphodynamic models (XBeach and Unibest‐TC).

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Section: Discussionmentioning

confidence: 99%

Section: Theory and Methodologymentioning

confidence: 99%

Section: Theory and Methodologymentioning

confidence: 99%

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On the predictive skill of morphodynamic models for onshore sandbar migration

Hewageegana

Canestrelli

2021

Earth Surf Processes Landf

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“…It was suggested that the mechanism of bed level accretion was associated with three-dimensional (3-D) cell circulation (Aagaard et al, 1998a(Aagaard et al, , 2006, during which the onshore sediments transported by incident waves were not returned straightly seaward by weak offshore mean flows, but through alongshore feeders and rip channels, which eventually contribute to the infill of runnels landward of the bar crest and the weld of the bar to the beach face (Kroon and Masselink, 2002;Houser et al, 2006;Falqués et al, 2008). Under energetic wave conditions or stormy conditions, larger asymmetric incident waves broke at deeper locations once the breaker indices were approached, which lead to a wider and highly dissipative surf zone with high-energy water motions (Gallagher et al, 1998;Vidal-Ruiz and de Alegría-Arzaburu, 2020). As a result, the bed level at upper or whole beaches featured by the bar-trough system was strongly eroded, which was related to vertical undertow circulation (Quartel et al, 2008;Ribeiro et al, 2012;Brand et al, 2019).…”

Section: Introductionmentioning

confidence: 99%

ADV-Based Investigation on Bed Level Changes Over a Meso-Macro Tidal Beach

et al. 2021

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Beach intra-tidal bed level changes are of significance to coastal protection amid global climate changes. However, due to the limitation of instruments and the disturbance induced by wave motions superimposed on water levels, it was difficult to detect the high-frequency oscillation of the submerged beach bed level. In this study, an observation, lasting for 12 days and covering the middle tide to the following spring tide, was conducted on a meso-macro tidal beach, Yintan Beach, to simultaneously detect the characteristics and influence mechanism of bed level changes at intra-tidal and tidal cycle scales. The collected data included water depth, suspended sediment concentration (SSC), waves, high-frequency three-dimensional (3-D) velocity, and the distance of the seabed to the acoustic Doppler velocimeter (ADV) probe, which were measured by an optical backscatter sensor, two Tide & Wave Recorder-2050s, and an ADV, respectively. The results showed that the tidal cycle-averaged bed level decreased by 58.8 mm, increased by 12.6 mm, and increased by 28.9 mm during neap, middle, and spring tides in succession, respectively, compared with the preceding tidal regimes. The net erosion mainly resulted from large incident wave heights and the consequent strong offshore-directed sediment transport induced by undertows. Moreover, the variations in the bed level were more prominent during a neap to middle tides than during middle to spring tides, which were jointly caused by the wave-breaking probability regulated by water depth and the relative residence times of shoaling wave, breaker, and surf zones that were determined by relative tidal range. In terms of the intra-tidal bed level, it displayed an intra-tidal tendency of increase during floods and decrease during ebb tides, i.e., the intra-tidal bed level changes were controlled by water depth, which modulated the effects of waves on sediment resuspension and vertical sediment exchange. To be specific, waves and SSC were responsible for the intra-tidal bed level changes under low-energy wave conditions, while mean current and bedform exerted important influences on the variations of the intra-tidal bed level under moderate wave conditions, which broke the foregoing interrelation between bed level, waves, and SSC. This study, therefore, emphasizes the usage of ADV measurement to investigate bed level changes in sandy coasts.

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Sediment pathways and morphodynamic response to a multi-purpose artificial reef – New insights

Silva

Hamilton

Strauss

et al. 2022

Coastal Engineering

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Multi-purpose Artificial Reefs (MPARs) are structures that may provide aesthetically acceptable coastal protection and improve recreational outcomes. Twenty years after construction of the first MPAR, Narrowneck reef on the Gold Coast of Australia, most of the available literature is still focused on the planning, design and construction of such structures and peer-reviewed publications on their post-construction monitoring, interaction with sediment transport and impacts on coastal morphology are lacking. The aim of this paper is to evaluate how does Narrowneck reef influence the sediment transport, and morphological changes around the anthropogenic structure, two decades after construction. To do so, a combination of ten high spatial resolution topo-bathymetric surveys from the top of the dune to the 10 m depth captured over 21 months and a series of 60 simulations using a calibrated numerical model were used. Our results demonstrate that: although not expected during design or reported in similar structures, sand can bypass the MPAR around its offshore end; under oblique waves, the longshore currents are deflected as they pass the reef, resulting in a shadow zone on the downdrift side where sand deposits; the bar crest tends to be higher on the reef's updrift side compared to downdrift, indicating that the MPAR can act as a store for sediments, as initially designed. Furthermore, the MPAR can act to stabilise the bar as it moves onshore with a downdrift offset of the inner bar as a result of low oblique wave incidence. The results presented here demonstrate that the short-term response to the MPAR twenty years after construction is more closely related to the deflection of longshore currents as they encounter the reef than to the dissipation of wave energy. This is because MPARs are designed to dissipate just enough wave energy so that they can achieve their recreational goal (surfing).

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Modes of onshore sandbar migration at a single-barred and swell-dominated beach

Cited by 10 publications

References 25 publications

On the predictive skill of morphodynamic models for onshore sandbar migration

On the predictive skill of morphodynamic models for onshore sandbar migration

ADV-Based Investigation on Bed Level Changes Over a Meso-Macro Tidal Beach

Sediment pathways and morphodynamic response to a multi-purpose artificial reef – New insights

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