Theoretical and Observed Breaking Wave Height on a Barred Macrotidal Beach: Implications for the Estimation of Breaker Index on Beaches with Large Tidal Range

Héquette, Arnaud; Cartier, Adrien

doi:10.2112/si75-173.1

Cited by 7 publications

(5 citation statements)

References 10 publications

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“…Field observations indicated that the inshore wave data better reflected the wave conditions encountered at the study site, therefore were favoured over the nearshore alternative. Furthermore, Héquette and Cartier (2016) recommend the use of wave parameters recorded closer to shore opposed to data derived offshore as a greater degree of interaction with seafloor bathymetry alters wave characteristics.…”

Section: Wave Climate and Tidal Regimementioning

confidence: 99%

Quantification of contemporary storm‐induced boulder transport on an intertidal shore platform using radio frequency identification technology

Hastewell

Inkpen

Bray

et al. 2020

Earth Surf Processes Landf

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Extreme storm events are known to produce, entrain, transport and deposit sizable boulders along rocky coastlines. However, the extent to which these processes occur under moderate, fetch‐limited wave conditions is seldom considered. In this study we quantify boulder transport at a relatively sheltered location subject to high‐frequency, low‐magnitude storm activity. This was achieved by deploying radio frequency identification (RFID) tags within 104 intertidal limestone boulders ranging in size from fine to very coarse (intermediate axis: 0.27–2.85 m). The study was conducted over 3 years (July 2015–July 2018) and encompassed numerous storm events. Tagged boulders were relocated during 17 field surveys and their positions recorded using a differential global positioning navigation satellite system (DGNSS). On completion, we identified boulder displacement in 69% of the tagged array. The accrued boulder transport distance amounted to 233.0 m from 195 incidents of displacement, including the movement of a boulder weighing an estimated 11.9 t. Transport was not confined to autumn and winter storms alone, as displacement was also recorded during summer months (April–September), despite the seasonally reduced wave magnitude. Boulder production by wave quarrying was documented in three tagged clasts, confirming observations that the shore platform is actively eroding. Incidents of overturning during transport were also recorded, including multiple overturning of clasts weighing up to 5 t. We further identify a statistically significant difference (maximum p‐value ≤ 0.03) between the transport distances attributed to constrained and unconstrained boulders, suggesting that the pre‐transport morphological setting exerts considerable control over boulder transport potential. The findings establish low to moderate storm waves as a key component in the evolution of the study site. More broadly, we claim that high‐frequency, low‐magnitude storms regularly modify these overlooked rocky coastal locations, suggesting that the hydrodynamic capability at such sites may previously have been underestimated. © 2020 John Wiley & Sons, Ltd.

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Section: Wave Climate and Tidal Regimementioning

confidence: 99%

Quantification of contemporary storm‐induced boulder transport on an intertidal shore platform using radio frequency identification technology

Hastewell

Inkpen

Bray

et al. 2020

Earth Surf Processes Landf

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“…In this relatively short-fetch environment, the modal offshore significant wave height is less than 1 m with wave periods typically ranging from 4 to 8 s, although maximum wave height may episodically exceed 5 m with periods of 9 to 10 s during major storms [45]. However, waves undergo significant shoaling and energy dissipation over the massive inner shelf sand banks (Figure 1A) and the gentle beach and nearshore slopes that characterize the coast of Northern France, resulting in significantly lower wave heights at the coast [37]. The prevailing winds in the region are from west to southwest, with a secondary wind direction from north to northeast [44].…”

Section: Study Areamentioning

confidence: 99%

“…Breaking wave height, for example, is often a required parameter for computing longshore sediment transport on beaches [27,28] or for modelling coastal dune erosion [29][30][31] whereas breaker heights in many morphodynamic models are frequently indirectly derived from a semiempirical breaking index (e.g., [32,33]. Values of wave height at breaking can be obtained through numerical modelling (e.g., [34,35]) or from in situ measurements of water surface elevation changes using a variety of acoustic or pressure sensors [36,37] or of flow data that can be transformed to surface elevation spectra [38,39]. However, the actual wave height at the breakpoint is often difficult to determine from direct measurements of flow or surface elevation data, since it can hardly be ascertained whether wave heights were obtained during breaking or non-breaking conditions.…”

Section: Introductionmentioning

confidence: 99%

The Effects of Tidal Translation on Wave and Current Dynamics on a Barred Macrotidal Beach, Northern France

Héquette

Cartier²,

Schmitt

2021

JMSE

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Barred macrotidal beaches are affected by continuous horizontal displacements of different hydrodynamic zones associated with wave transformation (shoaling, breaker and surf zones) due to significant tide-induced water level changes. A series of wave and current meters, complemented by a video imagery system, were deployed on a barred beach of northern France during a 6-day experiment in order to characterize the spatial and temporal variability of wave-induced processes across the beach. Wave and current spectral analyses and analyses of cross-shore current direction and asymmetry resulted in the identification of distinct hydrodynamic processes, including the development of infragravity waves and offshore-directed flows in the breaker and surf zones. Our results revealed a high spatial variability in the hydrodynamic processes across the beach, related to the bar-trough topography, as well as significant variations in the directions and intensity of cross-shore currents at fixed locations due to the horizontal translation of the different hydrodynamic zones resulting from continuous changes in water level due to tides.

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“…The modal offshore significant wave height is approximately 0.6 m, with wave periods typically ranging from 4 to 8 s, but the maximum wave height may episodically exceed 4 m, with periods of 9 to 10 s during major storms [51]. Wave heights are significantly lower at the coast, due to significant shoaling and energy dissipation over the shallow offshore sand banks, resulting in wave heights that hardly exceed 1 m in the intertidal zone, even during storms [52,53].…”

Section: Wavesmentioning

confidence: 99%

Mesoscale Morphological Changes of Nearshore Sand Banks since the Early 19th Century, and Their Influence on Coastal Dynamics, Northern France

Latapy

Héquette

Pouvreau

et al. 2019

JMSE

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Tidal sand banks are common along the coast of northern France facing the North Sea, where they form linear shore-parallel or slightly oblique sand bodies from shallow coastal areas to depths of tens of meters. Hydrographic surveys have been carried out since the 1830s for mapping the seabed of the coastal zone. An analysis of the bathymetry evolution shows significant morphological changes have occurred across the shoreface since the early 19th century, largely due to cross-shore and longshore sand bank migration. Our results show that nearshore sand banks mainly migrated onshore and gained sediment, especially during the 20th century; acting as temporary sediment sinks, which can in turn serve as sand sources for providing sediment to the coast. Alongshore, the migration and elongation of sand banks can be related to tidal asymmetry that is mostly directed to the east-north-east in the region. Shore-perpendicular movement can likely be explained by the action of shore-normal storm-waves in the nearshore zone after their refraction over shallow offshore sand banks. A seaward displacement of sand banks was also observed. This may be related to the combined action of waves and tidal currents which can induce erosion on one side of the bank, decreasing its width, and eventually leading to its seaward migration. Our observations point out that some nearshore sand banks respond to the action of currents and waves, and interact between each other via feedback morphodynamic processes induced by sand bank morphological changes. The substantial morphologic changes that affected the nearshore zone of northern France during the last centuries probably had large impacts on coastal hydrodynamics and associated shoreline evolution.

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Theoretical and Observed Breaking Wave Height on a Barred Macrotidal Beach: Implications for the Estimation of Breaker Index on Beaches with Large Tidal Range

Cited by 7 publications

References 10 publications

Quantification of contemporary storm‐induced boulder transport on an intertidal shore platform using radio frequency identification technology

Quantification of contemporary storm‐induced boulder transport on an intertidal shore platform using radio frequency identification technology

The Effects of Tidal Translation on Wave and Current Dynamics on a Barred Macrotidal Beach, Northern France

Mesoscale Morphological Changes of Nearshore Sand Banks since the Early 19th Century, and Their Influence on Coastal Dynamics, Northern France

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