Storm-generated morphological change and longshore sand transport in the intertidal zone of a multi-barred macrotidal beach

Sédrati, Mouncef; Anthony, Edward J.

doi:10.1016/j.margeo.2007.07.002

Cited by 64 publications

(52 citation statements)

References 27 publications

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“…Significant wave heights vary markedly as waves cross the bar and as a function of the tide-influenced water depths. Wave heights over the bar are at a maximum at high tide and decrease with the water level, in agreement with other studies on macrotidal beaches [Russell et al, 1991;Voulgaris et al, 1996;Levoy et al, 2001;Anthony et al, 2004Anthony et al, , 2005Reichmüth and Anthony, 2007;Sedrati and Anthony, 2007]. Wave attenuation increases as depths decrease until emersion of the crest of the bar.…”

Section: Study Areasupporting

confidence: 91%

Short‐term to decadal‐scale onshore bar migration and shoreline changes in the vicinity of a megatidal ebb delta

Robin¹,

Levoy²,

Monfort³

et al. 2009

J. Geophys. Res.

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[1] Swash bar development has been well documented from coasts with low to moderate tidal ranges, while studies of the effects of these forms on the morphology and dynamics of the adjacent shore in large tide range environments are rare. The analysis of sequential vertical aerial photographs was combined with field work in order to highlight the effects of swash bar development on the adjacent shoreline in the vicinity of a megatidal inlet (mean spring tidal range of 11 m). Swash bars are observed to form on the ebb tidal delta and to migrate landward before welding onto the coast. A close relationship was noticed between the position of the swash bar and shoreline dynamics. The bar protects the shore against wave attack in a sedimentary system controlled by longshore transport. This protective role is, however, modulated by the large tidal range. As the bar migrates upward toward the high-tide level and the subaerial beach, it develops morphologically into a transverse form that acts as a cross-shore obstacle to longshore sediment transport, thus resulting in shoreline accretion updrift and in strong erosion downdrift. This disturbance may persist for years because of the relatively slow speed of movement of the bar at this stage, an aspect characteristic of large tide range environments. This pattern of behavior differs fundamentally from that documented in the literature where the perturbation of the longshore sediment transport occurs over shorter periods. An original conceptual model of swash bar morphodynamics and repercussions on the adjacent shoreline for this megatidal environment is proposed.Citation: Robin, N., F. Levoy, O. Monfort, and E. Anthony (2009), Short-term to decadal-scale onshore bar migration and shoreline changes in the vicinity of a megatidal ebb delta,

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Section: Study Areasupporting

confidence: 91%

Short‐term to decadal‐scale onshore bar migration and shoreline changes in the vicinity of a megatidal ebb delta

Robin¹,

Levoy²,

Monfort³

et al. 2009

J. Geophys. Res.

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“…1C), largely consists of wide, gently sloping, sandy bar-trough beaches Anthony, 2007, 2008;Sedrati and Anthony, 2007), and of low-elevated coastal dunes that rarely exceed 15 m high (Ruz et al, 2005;Anthony et al 2006). The shoreface is characterised by the presence of numerous linear sand banks (Augris et al, 1990;Beck et al, 1991), sub-parallel to the shoreline, the evolution of which mainly depends on the action of tidal currents and storm waves (Tessier et al, 1999).…”

Section: Gulf Of Lionsmentioning

confidence: 99%

Morphodynamics of beach/dune systems: examples from the coast of France

Sabatier¹,

Anthony²,

Héquette³

et al. 2009

geomorphologie

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“…Initially based solely on bathymetric surveys (e.g., Ruessink and Kroon, 1994), but more recently relying for its data collection on Argus video cameras (e.g., van Enckevort et al, 2004;Armaroli and Ciavola, 2011), these studies focus on the quantification and explanation of bar migration and evolution. Without exception, all research into outer bar dynamics has been carried out in either micro-or meso-tidal environments, i.e., settings with the mean spring tide (MSR) range less than 4 m. Intertidal bars are well known to occur in macro-tidal settings (e.g., Masselink and Anthony, 2001;van Houwelingen et al, 2006a, b;Sedrati and Anthony, 2007), but outer bars have only been reported from macro-tidal settings in passing (e.g., Austin et al, 2010Austin et al, , 2013Austin et al, , 2014Scott et al, 2011;) and no systematic description of their morphology and dynamics has yet been presented.…”

Section: Introductionmentioning

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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Storm-generated morphological change and longshore sand transport in the intertidal zone of a multi-barred macrotidal beach

Cited by 64 publications

References 27 publications

Short‐term to decadal‐scale onshore bar migration and shoreline changes in the vicinity of a megatidal ebb delta

Short‐term to decadal‐scale onshore bar migration and shoreline changes in the vicinity of a megatidal ebb delta

Morphodynamics of beach/dune systems: examples from the coast of France

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

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