Morphodynamic response of a meso- to macro-tidal intermediate beach based on a long-term data set

Sénéchal, Nadia; Gouriou, Thomas; Castelle, Bruno; Parisot, J. P.; Capo, Sylvain; Bujan, Stéphane; Howa, Hélène

doi:10.1016/j.geomorph.2008.12.016

Cited by 74 publications

(45 citation statements)

References 45 publications

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“…Given these conditions, the most economic and widespread (Wijnberg et al, 2005;Turner and Anderson, 2007;Kroon et al, 2007) is based on the registration of changes in the shoreline position using time-average images (timex), collected by a local video-camera station, where the swash effects are eliminated (Pardo-Pascual et al, 2014;Alvarez-Ellacuria et al, 2011). Compared to other indicators proposed as a proxy for the impact of storms, datum-based shoreline position has some specific advantages: it is possible to visually interpret the evolution in terms of shifts and rotations (if any), continuous images can be taken, even during storm peaks (which is only possible by using a remote sensor), it is a rather unsupervised and cheap approach, and it basically does not interfere with the environment (Alvarez-Ellacuria et al, 2011;Sénéchal et al, 2009). In contrast, occasional detection of sporadic shorelines through traditional methods such as GPS or satellite imagery can lead to unrealistic evolutionary beach trends Archetti, 2009).…”

Section: Introductionmentioning

confidence: 99%

Optimal index related to the shoreline dynamics during a storm: the case of Jesolo beach

Archetti¹,

Paci²,

Carniel³

et al. 2016

Nat. Hazards Earth Syst. Sci.

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Abstract. The paper presents an application of shoreline monitoring aimed at understanding the response of a beach to single storms and at identifying its typical behaviour, in order to be able to predict shoreline changes and to properly plan the defence of the shore zone. On the study area, in Jesolo beach (northern Adriatic Sea, Italy), a video monitoring station and an acoustic wave and current profiler were installed in spring 2013, recording, respectively, images and hydrodynamic data. The site lacks previous detailed hydrodynamic and morphodynamic data.Variations in the shoreline were quantified in combination with available near-shore wave conditions, making it possible to analyse the relationship between the shoreline displacement and the wave features. Results denote characteristic patterns of beach response to storm events, and highlight the importance of improving beach protection in this zone, notwithstanding the many interventions experimented in the last decades. A total of 31 independent storm events were selected during the period October 2013-October 2014, and for each of them synthetic indexes based on storm duration, energy and maximum wave height were developed and estimated. It was found that the net shoreline displacements during a storm are well correlated with the total wave energy associated to the considered storm by an empirical power law equation. A sub-selection of storms in the presence of an artificial dune protecting the beach (in the winter season) was examined in detail, allowing to conclude that the adoption of this coastal defence strategy in the study area can reduce shoreline retreat during a storm. This type of intervention can sometimes contribute to prolonging overall stability not only in the replenished zone but also in downdrift areas.The implemented methodology, which confirms to be economically attractive if compared to more traditional monitoring systems, proves to be a valuable system to monitor beach erosive processes and provide detailed indications on how to better plan beach-maintenance activities. The presented methodology and the proposed results can therefore be used as a basis for improving the collaboration between coastal scientists and managers to solve beach erosion problems, in locations where data are scattered and sporadic.

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Section: Introductionmentioning

confidence: 99%

Optimal index related to the shoreline dynamics during a storm: the case of Jesolo beach

Archetti¹,

Paci²,

Carniel³

et al. 2016

Nat. Hazards Earth Syst. Sci.

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“…Van Enckevort et al, 2004;Ruessink et al, 2007a), spatially limited to (an alongshore transect of) the inner bar (e.g. Lippmann and Holman, 1990;Shand et al, 2003;Sénéchal et al, 2009) or based on data acquired at different locations or at irregular intervals (Short and Aagaard, 1993;Castelle et al, 2007). Furthermore, the large relaxation times of outer bars, in relation to the offshore wave forcing, have often prevented an abundance of state transitions of the outer bar to occur during the studied periods (see e.g.…”

Section: Alongshore Sandbar Variabilitymentioning

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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“…In order to investigate the temporal variability of the beach and how it could be linked to climate variability, we analysed a 14-yr topographic dataset, and compared it to wave data. The data used was from regular topographic surveys that have been carried out at Truc Vert beach by the EPOC laboratory (EPOC: Environnements et Paléoenviron-nements Océaniques et Continentaux) at the University of Bordeaux 1 since 1997 (Sénéchal et al 2009). Surveys are carried out monthly at spring low tides from the dune foot to the low-tide waterline, resulting in beach profile data with an average cross-shore length of about 400 m, using a theodolite from 1997 to 2003 and a kinematic GPS since 2003.…”

Section: Data Analysis: Beach Dynamics and Temporal Variabilitymentioning

confidence: 99%

Vulnerability of sandy coasts to climate variability

Idier¹,

Castelle²,

Poumadère³

et al. 2013

Clim. Res.

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The main objective of the VULSACO (VULnerability of SAndy COasts to climate change and anthropic pressure) project was to investigate present day and potential future vulnerability of sandy coasts at the 2030 horizon, i.e. on a time scale related to climate variability. The method, based on a multidisciplinary approach bringing together geologists, geographers, physicists, social psychologists, engineers and stakeholders, was structured around 4 axes: field data analysis; numerical modelling; analysis of governance and stakeholder perceptions; and development of vulnerability indexes. This approach was designed to investigate vulnerability at a local scale and was applied to 4 contrasting beaches located in France: Sète Lido (Mediterranean Sea), Truc Vert and La Tresson beaches (Atlantic Ocean), and Dewulf (English Channel). The results focus on decadal and multi-annual beach trends at the Truc Vert beach site. There is almost no trend in beach volume at Truc Vert beach, although there is a variation in this parameter on a cycle of 2 to 3 yr, with variations related to wave energy and probably to indexes of climate variability. Numerical modelling identified the sensitivity of beach responses to changes in wave height and direction, especially in terms of subtidal morphology and the potential development of shoreline instability. Together with the observed offshore wave angle at the Biscay Buoy, these model results suggest that a potential change in wave angle due to climate variability could significantly modify the bars' morphology. The combination of data analysis and numerical modelling contributed to the development of vulnerability indexes designed for sandy coasts, which take into account climate-dependant variables such as waves. This allowed the differentiation of the sites in terms of vulnerability to erosion: Sète Lido and Truc Vert beach were the most and least vulnerable sites, respectively. These indexes help in identifying the dominant components of beach vulnerability, and provide potential for the study of how anthropogenic factors affect vulnerability. The study of stakeholder perceptions and decision-making with regard to climate-related risk also highlighted potential anthropogenic effects on beach vulnerability, and identified possible site-specific outcomes.

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Morphodynamic response of a meso- to macro-tidal intermediate beach based on a long-term data set

Cited by 74 publications

References 45 publications

Optimal index related to the shoreline dynamics during a storm: the case of Jesolo beach

Optimal index related to the shoreline dynamics during a storm: the case of Jesolo beach

Morphological coupling in multiple sandbar systems – a review

Vulnerability of sandy coasts to climate variability

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