Seasonal morphological response of an open sandy beach to winter wave conditions: The example of Biscarrosse beach, SW France

Biausque, Mélanie; Sénéchal, Nadia

doi:10.1016/j.geomorph.2019.02.009

Cited by 35 publications

(24 citation statements)

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“…In temperate regions, the main driver of episodic beach erosion events is extratropical cyclones (Harley et al, 2017a;Biausque and Senechal, 2019;Dodet et al, 2019), and changes in storm wave climates may cause significantly greater coastal erosion than sea level rise (Cowell et al, 1995;Slott et al, 2006;Hemer et al, 2012). Recent research has highlighted that for open coast beaches, storm waves coming from atypical directions can expose normally protected beaches to high-energy waves, which can cause severe erosion (Harley et al, 2017a).…”

Section: Introductionmentioning

confidence: 99%

Wave direction shift triggered severe erosion of beaches in estuaries and bays with limited post‐storm recovery

Gallop

Vila‐Concejo

Fellowes

et al. 2020

Earth Surf Processes Landf

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Many estuaries contain sandy beaches that provide habitats and offer protective buffers for wetlands and infrastructure, alongside cultural and recreational resources. Research underpinning coastal management tends to focus on tide‐ and swell‐dominated sandy beaches, but little attention is given to beaches in estuaries and bays (BEBs) that exist along a continuum of wind/swell wave, tide and riverine influence. BEBs are subject to less wave energy than open coast locations because of the generally narrow window of directions for which ocean waves can propagate through the entrance. However, when storm wave direction coincides with the orientation of the estuary or bay entrance, waves can penetrate several kilometres inside. Here we focus on eight BEBs in two major bays/estuaries in Sydney, Australia and present observations from before and after a major extratropical storm with waves from an atypical direction in June 2016. We quantify magnitudes of beach erosion and recovery rates for 3 years post‐storm. We show that when high‐energy storm waves penetrate bays and estuaries, BEBs can undergo up to 100% of subaerial beach erosion. Three years after the storm, only 5 of the 29 (17%) eroded subaerial beach profiles had recovered to their pre‐storm volume. This is likely due to the lack of low‐frequency, beach‐building waves at BEBs under modal weather conditions in between storms, in contrast to open coast beaches. We also show that the recovery of BEBs may be limited by the absence of adjacent sediment reservoirs due to the dominance of tidal processes mid‐channel. Our study highlights the unique behaviour of BEBs relative to beaches on the open coast, and that shifting wave direction needs to be considered in long‐term beach resilience under climate change. © 2020 John Wiley & Sons, Ltd.

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Section: Introductionmentioning

confidence: 99%

Wave direction shift triggered severe erosion of beaches in estuaries and bays with limited post‐storm recovery

Gallop

Vila‐Concejo

Fellowes

et al. 2020

Earth Surf Processes Landf

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“…Therefore, subsequent waves eroded sediment from around the shoreline generating a new equilibrium profile for these wave conditions. As a result, a certain wave energy can be required to mobilise stranded offshore sediments and to maintain the active beach profile [22,23].…”

Section: Introductionmentioning

confidence: 99%

Beach Profile Evolution towards Equilibrium from Varying Initial Morphologies

Eichentopf

Zanden

Caceres

et al. 2019

JMSE

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The evolution of different initial beach profiles towards the same final beach configuration is investigated based on large-scale experimental data. The same wave condition was performed three times, each time starting from a different initial profile morphology. The three different initial profiles are an intermediate energy profile with an offshore bar and a small swash berm, a plane profile and a low energy profile with a large berm. The three cases evolve towards the same final (equilibrium) profile determined by the same wave condition. This implies that the same wave condition generates different sediment transport patterns. Largest beach changes and differences in hydrodynamics occur in the beginning of the experimental cases, highlighting the coupling between morphology and hydrodynamics for beach evolution towards the same profile. The coupling between morphology and hydrodynamics that leads to the same final beach profile is associated with differences in sediment transport in the surf and swash zone, and is explained by the presence of bar and berm features. A large breaker bar and concave profile promote wave energy dissipation and reduce the magnitudes of the mean near-bed flow velocity close to the shoreline limiting shoreline erosion. In contrast, a beach profile with reflective features, such as a large berm and a small or no bar, increases negative velocity magnitudes at the berm toe promoting shoreline retreat. The findings are summarised in a conceptual model that describes how the beach changes towards equilibrium from two different initial morphologies.

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“…It is thus unlikely that volume changes as computed from cross-shore profile measurements separated by several months could be related to the largely changing meteo-marine conditions that were acting during that period of time. Additionally, it is worth noting that accounting for meteo-marine conditions this is not even necessarily enough for predicting the evolution, even over short time scales (see, e.g., Biausque and Senechal [25]. Indeed, field observations suggest that alongshore sand displacement driven by tide-and wave-currents might play a role in the intertidal bar morphology.…”

Section: Restrictions Of the Modelmentioning

confidence: 99%

“…As emphasized by [25], two approaches have been generally adopted to better study beach morphodynamics: long-term approach that is based on seasonal to decadal data, and recovery from dramatic events. This study focuses on the morphodynamics of sandy beaches characterized by an intertidal bars-trough system commonly found along meso-and macro-tidal environments by taking advantage of high-quality data sets (with high spatial resolution and a combination of low to high temporal resolutions) over a time span of 19 years along the Belgian coast.…”

Section: Introductionmentioning

confidence: 99%

“…The developed space-time model is thus used to predict the integrated sand volume change over time along these profiles. Relationships between the morphological development of the multi-barred beaches and controlling factors as meteo-marine conditions will be subject of future studies, as the main goal of the paper is to assess the ability of such a space-time model to predict sand volume change from data that where mostly sampled every few months, thus precluding the direct use of the direct use of meteo-marine factors at a much finer time scale, as done in [25]. As noted by [16], accurate sand volume estimation is required to monitor rates of beach erosion and accration, so sand volume change assessment is particularly relevant for beach preservation and management.…”

Section: Introductionmentioning

confidence: 99%

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Predicting Morphodynamics for Beach Intertidal Systems in the North Sea: A Space-Time Stochastic Approach

Bogaert

Montreuil

Chen

2020

JMSE

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The ability to accurately predict beach morphodynamics is of primary interest for coastal scientists and managers. With this goal in mind, a stochastic model of a sandy macrotidal barred beach is developed that is based on cross-shore elevation profiles. Intertidal elevation was monitored from monthly to annually for 19 years through Real Time Kinematics-GPS (RTK-GPS) and LiDAR surveys, and monthly during two years with an RTK-GPS. In addition, during two campaigns of about two weeks, intensive surveys on a daily basis were performed with an RTK-GPS on a different set of profiles. Based on the measurements, space and time variograms are constructed in order to assess the spatial and temporal dependencies of these elevations. A separable space-time covariance model is then built from them in order to generate a large number of plausible future profiles at arbitrary time instants t+τ, starting from observed profiles at time instants t. For each simulation, the total displaced sand volume is computed and a distribution is obtained. The mean of this distribution is in good agreement with the total displaced sand volume measured on the profiles, provided that they are lower than 45 m3/m. The time variogram also shows that 90% of maximum variability is reached for a time interval τ of three years. These results demonstrate how the temporal evolution of an integrated property, like the total displaced sand volume, can be estimated over time. This suggests that a similar stochastic approach could be useful for estimating other properties as long as one is able to capture the stochastic space-time variability of the underlying processes.

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Seasonal morphological response of an open sandy beach to winter wave conditions: The example of Biscarrosse beach, SW France

Cited by 35 publications

References 50 publications

Wave direction shift triggered severe erosion of beaches in estuaries and bays with limited post‐storm recovery

Wave direction shift triggered severe erosion of beaches in estuaries and bays with limited post‐storm recovery

Beach Profile Evolution towards Equilibrium from Varying Initial Morphologies

Predicting Morphodynamics for Beach Intertidal Systems in the North Sea: A Space-Time Stochastic Approach

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