Morphodynamic response of nearshore bars to a shoreface nourishment

Grunnet, Nicholas; Ruessink, Gerben

doi:10.1016/j.coastaleng.2004.09.006

Cited by 79 publications

(61 citation statements)

References 14 publications

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“…13, barline). This is in accordance with observations in other nearshore regions of an increase in the bar three-dimensionality after the execution of a shoreface nourishment (Grunnet and Ruessink, 2005). In that case, the authors related the augmentation of the bar 3D morphology to the reduction in the water depth over the bar.…”

Section: Bar Sinuositysupporting

confidence: 79%

Dynamics of single-barred embayed beaches

2011

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Keywords:subtidal sand bar nearshore morphodynamics video imagery artificial beach Barcelona MediterraneanThe dynamics of single submerged sandbars of two artificial embayed beaches (La Barceloneta and Bogatell, Barcelona, NW Mediterranean) has been studied with a video-recorded data set of 4.3 years. The alongshoreaveraged cross-shore migration, the orientation with respect the shoreline and the sinuosity of the barlines have been analyzed and related to wave conditions, alongshore sediment transport and shoreline variability. In general, the submerged bars follow the general cyclic morphological behaviour observed in natural beaches, switching among the four intermediate morphodynamic states, but the studied beaches can be arrested during long periods of low wave conditions. The dominant up-state transition in Barcelona beaches during storms is the transition toward the rhythmic bar and beach state, the complete morphodynamic reset (longshore bar and trough state) only occurring during extreme wave events. The cross-shore migration of bars is dominated by the weekly and interannual components. The interannual component shows an onshore bar migration trend at both beaches, in contrast with the net offshore migration observed in multibarred open beaches. Bar disposition is located progressively seaward in the dominant alongshore transport direction (i.e., oblique with respect to the shoreline). At La Barceloneta beach, shoreline and barline orientations change consistently and a significant correlation between the accumulated alongshore sediment transport and the associated change in bar orientation has been found, suggesting that alongshore transport can play a significant role in barline orientation. Finally, bar sinuosity increases during eastern storms in both beaches. This indicates that the formation of crescentic bars occurs for approximately shore-normal waves. Some of the differences observed in bar morphology and mobility in the two studied beaches are related to their different level of protection with respect to the incident waves (beach indentation).

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Section: Bar Sinuositysupporting

confidence: 79%

Dynamics of single-barred embayed beaches

2011

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“…Bathymetric surveys confirm this (Ojeda et al, 2008). The nourishment stopped the net offshore migration of the inner and outer subtidal sandbars, a sandbar response also seen at other nourished locations (e.g., Van Duin et al, 2004;Grunnet and Ruessink, 2005). The 2006 nourishment was implemented on top of the decaying 1998 nourishment and remained in the same location until the end of the study period.…”

Section: Uniform Behaviormentioning

confidence: 67%

“…This differs from the Terschelling nourishment, which caused a break-up of a shoreward located bar into several sections intersected by deep, obliquely oriented channels (Grunnet and Ruessink, 2005). That nourishment was implemented inside the bar zone, rather than offshore the bar zone as in Noordwijk.…”

Section: Discussionmentioning

confidence: 99%

Nearshore evolution at Noordwijk (NL) in response to nourishments, as inferred from Argus video imagery

Ruessink

Grinten

Vonhögen-Peeters

et al. 2012

NCK-days 2012 : Crossing Borders in Coastal Research : Jubilee Conference Proceedings

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We use an approximately 16-year long data set of daily low-tide video images to examine the effect of three consecutive nourishments on the temporal evolution of the subtidal sandbars and the low-tide water line at Noordwijk, The Netherlands. The data set starts in 1995, with shoreface nourishments implemented in 1998 and in 2006, and a "Zwakke Schakel" beach nourishment in 2007/2008. We find that, consistent with observations elsewhere, the shoreface nourishments halted the interannual, net-seaward migration of the two sandbars. Also, the first nourishment resulted in large-scale sandbar variability known as bar switching. The beach nourishment had no effect on the sandbars, other than an immediate 50-m seaward shift of the low-tide waterline and the inner sandbar. Neither the shoreface nor the beach nourishments were found to result in an increase or decrease in the number and cross-shore extent of rip channels. On the whole, the successive nourishments have reduced the natural dynamics of the Noordwijk coastal system.

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“…Many present-day soft engineering measures to improve coastal safety, such as shoreface nourishments, involve direct or indirect modifications to sandbars (e.g. Grunnet and Ruessink, 2005;Ojeda and Guillén, 2008). A comprehensive understanding of the processes that govern sandbar behaviour and the development of the capability to predict this behaviour are thus of significant importance when it comes to minimising human and economic losses.…”

Section: Introductionmentioning

confidence: 99%

Morphological coupling in multiple sandbar systems – a review

Price

Ruessink

Castelle³

2014

Earth Surf. Dynam.

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Abstract. Subtidal sandbars often exhibit alongshore variable patterns, such as crescentic plan shapes and rip channels. While the initial formation of these patterns is reasonably well understood, the morphodynamic mechanisms underlying their subsequent finite-amplitude behaviour have been examined far less extensively. This behaviour concerns, among other aspects, the coupling of alongshore variable patterns in an inner bar to similar patterns in a more seaward bar, and the destruction of crescentic patterns. This review aims to present the current state of knowledge on the finite-amplitude behaviour of crescentic sandbars, with a focus on morphological coupling in double sandbar systems. In this context we include results from our recent study, based on a combination of remote-sensing observations, numerical modelling and data-model integration. Morphological coupling is an inherent property of double sandbar systems, where the inner bar may attain a type of morphology not found in single bar systems. Coupling is governed by water depth variability along the outer-bar crest and by various wave characteristics, including the offshore wave height and angle of incidence. In recent research, the role of the angle of wave incidence for sandbar morphodynamics has received more attention. Numerical modelling results have demonstrated that the angle of wave incidence is crucial to the flow pattern, sediment transport, and thus the emerging morphology of the coupled inner bar. Moreover, crescentic patterns predominantly vanish under highangle wave conditions, highlighting the role of alongshore currents in straightening sandbars and challenging the traditional conception that crescentic patterns vanish under high-energy, erosive wave conditions only.

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Morphodynamic response of nearshore bars to a shoreface nourishment

Cited by 79 publications

References 14 publications

Dynamics of single-barred embayed beaches

Dynamics of single-barred embayed beaches

Nearshore evolution at Noordwijk (NL) in response to nourishments, as inferred from Argus video imagery

Morphological coupling in multiple sandbar systems – a review

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