Morphosedimentary multiyear changes on a barred coast (Gulf of Lions, Mediterranean Sea, France)

Barusseau, Jean-Paul; Radulescu, Metodiu; Descamps, Cyr; Akouango, Emile; Gerbe, Alain

doi:10.1016/0025-3227(94)90204-6

Cited by 26 publications

(15 citation statements)

References 14 publications

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“…More often, inner-bar rip channels possess remarkably smaller and more variable alongshore scales than the outer bar (e.g. Barusseau et al, 1994;Van Enckevort et al, 2004;Lafon et al, 2004Lafon et al, , 2005. This would suggest that morphological coupling does not play a substantial role in the overall double-sandbar dynamics.…”

Section: Discussionmentioning

confidence: 93%

Coupling mechanisms in double sandbar systems. Part 1: patterns and physical explanation

Castelle

Ruessink

Bonneton

et al. 2010

Earth Surf Processes Landf

113

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Crescentic sandbars and rip channels along wave-dominated sandy beaches are relevant to understand localized beach and dune erosion during storms. In recent years, a paradigm shift from hydrodynamic template models to self-organization mechanisms occurred to explain the formation of these rhythmic features. In double sandbar systems, both the inner-and outerbar rip channels and crescentic planshapes are now believed to be free instabilities of the nearshore system arising through selforganization mechanisms alone. However, the occasional occurrence of one or two inner-bar rip channels within one outer-bar crescent suggests a forced, morphologically coupled origin. Here we use a nonlinear morphodynamic model to show that alongshore variability in outer-bar depth, and the relative importance of wave breaking versus wave focussing by refraction across the outer bar, is crucial to the inner-bar rip channel development. The coupling patterns simulated by our model are similar to those observed in the fi eld. Morphological coupling requires a template in the morphology (outer-bar geometry) which, through the positive feedback between fl ow, sediment transport and the evolving morphology (that is, self-organization) enforces the development of coupling patterns. We therefore introduce a novel mechanism that blurs the distinction between self-organization and template mechanisms. This mechanism may also be extended to explain the dynamics of other nearshore patterns, such as beach cusps. The impact of this novel mechanism on the alongshore variability of inner-bar rip channels is investigated in the companion paper.

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Section: Discussionmentioning

confidence: 93%

Coupling mechanisms in double sandbar systems. Part 1: patterns and physical explanation

Castelle

Ruessink

Bonneton

et al. 2010

Earth Surf Processes Landf

113

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“…For instance, the long sandy beaches with one or two sandbars at Duck, USA, and Hasaki, Japan, have been described by Kuriyama (2002) and Sallenger et al (1985), respectively. Examples of long sandy beaches with multiple bars are Terschelling, the Netherlands (Ruessink and Kroon, 1994), Wanganui, New Zealand (Shand et al, 1999), the Ebro Delta, Spain (Guillén and Palanques, 1993) and the beach barrier of Thau Lagoon, France (Barusseau et al, 1994). Singlebarred embayed beaches, however, have received less attention.…”

Section: Introductionmentioning

confidence: 99%

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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“…Recently, in the framework of the recent paradigm shift from template forcing theory to self-organization mechanisms (Coco and Murray, 2007), both linear stability models (Deigaard et al, 1999;Falqués et al, 2000;Damgaard et al, 2002;Calvete et al, 2005) and nonlinear morphodynamic models (Damgaard et al, 2002;Reniers et al, 2004;Castelle et al, 2006;Klein and Schuttelaars, 2006;Drønen and Deigaard, 2007;Garnier et al, 2008;Smit et al, 2008) have established that these 3D surfzone sandbars can be formed through self-organization mechanisms alone, and do not require a template in the hydrodynamics, as was previously proposed with the edge wave theory (Bowen and Inman, 1971;Holman and Bowen, 1982). Double sandbar systems are common morphological features along sandy, wave-dominated, micro-to meso-tidal coastlines (Lippmann et al, 1993;Barusseau et al, 1994;Ruessink et al, 2003;Van Enckevort et al, 2004;Castelle et al, 2007). In the cross-shore direction, the interactions between bars in multiple-barred settings have been recently touched upon.…”

Section: Introductionmentioning

confidence: 86%

“…More often, inner-bar rip channels possess remarkably smaller and more variable alongshore scales than the outer bar (Barusseau et al, 1994;Van Enckevort et al, 2004;Lafon et al, 2004Lafon et al, , 2005. Figure 1 shows a typical double sandbar system geometry with an outer bar exhibiting crescentic patterns at a narrow range of wavelength, which contrasts with highly alongshore-variable inner-bar rip channels.…”

Section: Introductionmentioning

confidence: 97%

Coupling mechanisms in double sandbar systems. Part 2: impact on alongshore variability of inner‐bar rip channels

Castelle

Ruessink

Bonneton

et al. 2010

Earth Surf Processes Landf

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Double sandbar systems are common morphological features along sandy, wave-dominated, micro-to meso-tidal coastlines. In the companion paper, we demonstrated how various alongshore inner-bar rip-channel patterns can develop through morphological coupling to an alongshore-variable outer bar. The simulated coupling patterns are, however, scarcely observed in the fi eld. Instead, inner-bar rip channels more often possess remarkably smaller and more variable alongshore length scales, suggesting that coupling mechanisms do not play a substantial role in the overall double-sandbar dynamics. Here we use a numerical model to show that the relative importance of self-organization and morphological coupling changes in favour of the latter with an increase in waterdepth variability along the outer-bar crest. Furthermore, we fi nd that the typical alongshore variability in inner-bar rip-channel scale is indicative of a mixture of self-organization and morphological coupling rather than self-organization alone. Morphological coupling may thus be more important to understanding and predicting the evolution of inner-bar rip channels than previously envisaged.

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Morphosedimentary multiyear changes on a barred coast (Gulf of Lions, Mediterranean Sea, France)

Cited by 26 publications

References 14 publications

Coupling mechanisms in double sandbar systems. Part 1: patterns and physical explanation

Coupling mechanisms in double sandbar systems. Part 1: patterns and physical explanation

Dynamics of single-barred embayed beaches

Coupling mechanisms in double sandbar systems. Part 2: impact on alongshore variability of inner‐bar rip channels

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