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Bruno Castelle - One of the best experts on this subject based on the ideXlab platform.
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video monitoring of Sandbar shoreline response to an offshore submerged structure at a microtidal beach
Geomorphology, 2017Co-Authors: Clement Bouvier, Yann Balouin, Bruno CastelleAbstract:Abstract In early 2013, an 800-m long and 12-m wide submerged breakwater with its crest in 2-m depth was implemented at the wave-dominated barred beach of Sete, SE France, to fight against erosion and submersion hazards. Daily video images from April 2011 to April 2016 covering an alongshore distance of 3.5 km are used to analyse the response of both the Sandbar(s) and the shoreline to the structure implementation. Results show that the breakwater had a profound impact on the nearshore system, both shoreward of the structure and well away from it alongshore. A progressive rotation and linearisation of the Sandbar was observed shoreward of the submerged breakwater. This resulted in the splitting of the Sandbar adjacent to the structure during a net offshore Sandbar migration event driven by a severe storm in December 2013. The typical formation of a salient or tombolo was not observed. Instead, shoreline coupled to the Sandbar geometry, which resulted in a slight seaward migration of the shoreline in front of the structure. Overall, this study highlights that the role of the Sandbar is critical to shoreline response to the implementation of breakwaters on barred beaches.
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two and three dimensional double Sandbar system behaviour under intense wave forcing and a meso macro tidal range
Continental Shelf Research, 2010Co-Authors: Rafael Almar, Bruno Castelle, B G Ruessink, Nadia Senechal, Philippe Bonneton, Vincent MarieuAbstract:Abstract Five weeks of hourly, 10-min time-exposure video images were used to analyze the meso–macro-tidal double-barred Truc Vert Beach, SW France, under intense wave forcing. The four storms experienced, one of which with an offshore significant wave height over 8 m, induced dramatic changes in the double Sandbar system. The subtidal outer bar migrated offshore rapidly (up to 30–50 m/day) and its pre-existing crescentic pattern was wiped out. The seaward-protruding parts of the outer bar barely migrated offshore during the most intense storm, whereas a landward-protruding part was shed off. Over the entire study period, the outer-bar dynamics was dominated by alongshore-averaged changes rather than alongshore non-uniform changes, while the opposite was observed for the inner bar. In addition, the outer-bar dynamics was predominantly controlled by the time-varying offshore wave conditions, whereas the inner-bar dynamics was influenced largely by the tide-range variations. Our observations put forward the key role of morphological settings (the presence of a subtidal bar and its shape) and tidal range in governing inner-bar behaviour within a double Sandbar dynamics, and provide strong support for previous suggestions that Sandbars cannot be studied in isolation.
Reniers A.j.h.m. - One of the best experts on this subject based on the ideXlab platform.
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Behaviour of subtidal Sandbars in response to nourishments
'Elsevier BV', 2018Co-Authors: Radermacher M., De Schipper, Price Timothy, Huisman B.j.a., Aarninkhof S.g.j., Reniers A.j.h.m.Abstract:The behaviour of subtidal Sandbars can be strongly influenced by the introduction of sand nourishments in the coastal system. This study focuses on the impact of nourishments on subtidal bar behaviour at spatio-temporal scales beyond a single nourishment project. It aims to determine the long-term behaviour of subtidal Sandbars along an entire coastal cell, taking into account both the unnourished and nourished regime, and covering various types of nourishments. The analysis is based on over 50 years of Sandbar evolution along the Delfland coast, a 17-km long coastal cell at the Dutch North Sea coastline protected by groynes and maintained with frequent sand nourishments. Observations reveal clearly different Sandbar behaviour during the unnourished (first 20 years) and nourished periods of the dataset. Introduction of the first beach nourishments (nourished sand primarily placed at the subaerial beach) was found to stimulate Sandbar development along previously unbarred sections of the coast. Shoreface nourishments (nourished sand placed at the seaward face of the pre-existing subtidal Sandbar) tended to migrate shoreward rapidly at a rate of 20 to 60 m/year at this coast, thereby forcing the pre-existing Sandbar to weld to the dry beach. An abrupt transition of Sandbar dynamics was observed following a major nourishment operation (∼ 37.5 Mm3 of nourished sand) that covered the entire coastal cell. A new, shallow Sandbar formed with a degree of alongshore variability that was unprecedented at the Delfland coast over the full study period. These results imply that individual nourishments can influence the formation and migration of individual Sandbars, while continued nourishments can fundamentally change long-term Sandbar dynamics along an entire coastal cell.Green Open Access added to TU Delft Institutional Repository ‘You share, we take care!’ – Taverne project https://www.openaccess.nl/en/you-share-we-take-care Otherwise as indicated in the copyright section: the publisher is the copyright holder of this work and the author uses the Dutch legislation to make this work public.Coastal EngineeringEnvironmental Fluid Mechanic
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Long-term bar dynamics using satellite imagery: A case study at Anmok beach, South Korea
'Coastal Engineering Research Council', 2018Co-Authors: Athanasiou Panagiotis, De Schipper, De Boer W.p., Tonnon, Pieter Koen, Yoo Jeseon, De Vries S., Ranasinghe Roshanka, Reniers A.j.h.m.Abstract:Nearshore Sandbar patterns can affect the hydrodynamics and, as a result, the beach morphodynamics in the nearshore zone. Hence, spatial and temporal variability in the Sandbars can influence beach accretion and erosion. Understanding the variability of the Sandbar system can therefore be crucial for informed coastal zone management. So far, the methods to study Sandbar dynamics mainly include datasets of video observations or occasional bathymetric surveys. However, at most locations around the world, these types of data are not or only scarcely available. In this paper we present an alternative method to analyze long-term Sandbar variability by means of freely available satellite imagery. These images are globally available since the 1980’s and, thus, have the potential to be applicable at any location in the world. Here, we will illustrate the methodology by means of a case study at Anmok beach at the South Korean East coast.Rivers, Ports, Waterways and Dredging EngineeringCoastal EngineeringEnvironmental Fluid Mechanic
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Analysing decadal-scale crescentic bar dynamics using satellite imagery: A case study at Anmok beach, South Korea
'Elsevier BV', 2018Co-Authors: Athanasiou Panagiotis, De Boer W.p., Yoo Jeseon, Ranasinghe Roshanka, Reniers A.j.h.m.Abstract:Understanding long-term Sandbar dynamics can be crucial for informed coastal zone management, but is often hampered by data availability. To increase the number of Sandbar observations available from bathymetric surveys, this study proposes and evaluates a method to manually extract the Sandbar location using freely available satellite imagery for the case study of Anmok beach in South Korea. Validation of the satellite extracted Sandbar locations against 9 in-situ measurements shows good agreement with errors well within the pixel resolution of the satellite imagery (i.e. 30 m for Landsat missions). The applicability of the method is constrained to locations where (1) the cross-shore crescentic length scales are larger than the image resolution, (2) frequent wave breaking and clouds are absent and (3) the water clarity is sufficient to enable the manual extraction of the Sandbar crest line. Using the additional Sandbar observations from the satellite imagery significantly increases the temporal extent and resolution of the dataset for Anmok beach. This allows the study of Sandbar characteristics, dynamics and impacts of human interventions to an extent that would not have been possible without the satellite imagery. Within the study period 1990–2017 it is found that the Sandbar maintains a persistent crescentic pattern that is only altered during prolonged and very intense storm conditions. The cumulative alongshore migration of the Sandbars is investigated and found to be in the order of hundreds of meters over the 27 years study period. Comparing the Sandbar characteristics prior and after the construction of Gangneung port shows that both the amplitudes and wavelengths of the Sandbar crescents near the port have decreased after its construction
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Analysing decadal-scale crescentic bar dynamics using satellite imagery: A case study at Anmok beach, South Korea
'Elsevier BV', 2018Co-Authors: Athanasiou Panagiotis, De Boer W.p., Yoo Jeseon, Ranasinghe Roshanka, Reniers A.j.h.m.Abstract:Understanding long-term Sandbar dynamics can be crucial for informed coastal zone management, but is often hampered by data availability. To increase the number of Sandbar observations available from bathymetric surveys, this study proposes and evaluates a method to manually extract the Sandbar location using freely available satellite imagery for the case study of Anmok beach in South Korea. Validation of the satellite extracted Sandbar locations against 9 in-situ measurements shows good agreement with errors well within the pixel resolution of the satellite imagery (i.e. 30 m for Landsat missions). The applicability of the method is constrained to locations where (1) the cross-shore crescentic length scales are larger than the image resolution, (2) frequent wave breaking and clouds are absent and (3) the water clarity is sufficient to enable the manual extraction of the Sandbar crest line. Using the additional Sandbar observations from the satellite imagery significantly increases the temporal extent and resolution of the dataset for Anmok beach. This allows the study of Sandbar characteristics, dynamics and impacts of human interventions to an extent that would not have been possible without the satellite imagery. Within the study period 1990–2017 it is found that the Sandbar maintains a persistent crescentic pattern that is only altered during prolonged and very intense storm conditions. The cumulative alongshore migration of the Sandbars is investigated and found to be in the order of hundreds of meters over the 27 years study period. Comparing the Sandbar characteristics prior and after the construction of Gangneung port shows that both the amplitudes and wavelengths of the Sandbar crescents near the port have decreased after its construction.Green Open Access added to TU Delft Institutional Repository ‘You share, we take care!’ – Taverne project https://www.openaccess.nl/en/you-share-we-take-care Otherwise as indicated in the copyright section: the publisher is the copyright holder of this work and the author uses the Dutch legislation to make this work public.Rivers, Ports, Waterways and Dredging EngineeringEnvironmental Fluid Mechanic
Kristen D Splinter - One of the best experts on this subject based on the ideXlab platform.
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cross shore Sandbars response to an artificial reef an intersite comparison
Coastal Sediments 2019, 2019Co-Authors: Clement Bouvier, Kristen D Splinter, B Castelle, Y Balouin, M Blacka, B DubarbierAbstract:While a clear improvement concerning aesthetic considerations using soft submerged breakwater is undeniable, their design has often focused on wave energy decrease in their lee, overlooking their impact on the dynamics of the nearby nearshore Sandbar(s). At the beach of Sete (southeast France), the submerged structure clearly affects the natural net offshore migration cycle (NOM) of the former double barred beach. On the contrary, at Narrowneck (Queensland, Australia), the deployment of a multi-functional submerged structure does not affect the cross-shore Sandbar processes. These contrasting behaviors are addressed using high frequency video monitoring. After discussing observations at both field sites, a process-based morphodynamic model provides insight into the morphological Sandbars response to artificial reefs.
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shoreline recovery on wave dominated sandy coastlines the role of Sandbar morphodynamics and nearshore wave parameters
Marine Geology, 2017Co-Authors: Matthew S Phillips, Mitchell D Harley, Ian L Turner, Kristen D Splinter, Ron CoxAbstract:Abstract This study quantifies and characterises the temporal variability of shoreline recovery on a high-energy sandy coastline using a 10-year dataset of daily shoreline and Sandbar positions from a Coastal Imaging station at Narrabeen-Collaroy Beach, Australia. Following a total of 82 individual storm events, rates of the cross-shore return of the shoreline to its pre-storm position were analysed. Observed rates during shoreline recovery were characterised by an overall mean of ~ 0.2 m/day. Temporal variability in rates was most evident at shorter timescales of 1–2 weeks and included rates most frequently between 0 and 0.3 m/day, less frequent more rapid rates of up to 2 m/day and also minor landward movements. This temporal variability was significantly correlated with nearshore forcing parameters describing the ratio of wave height to wave period, the cross-shore proximity (and attachment) of the Sandbar to the shoreline and the rate of cross-shore Sandbar migration. These findings are summarised in a new conceptual model that characterises temporal phases and rates of shoreline recovery corresponding to stages of onshore Sandbar migration following a storm, from fully detached storm-deposited Sandbar morphology through to complete Sandbar welding with the shoreline. More gradual shoreline recovery rates are observed with fully detached and semi-attached Sandbar conditions. In contrast, more rapid rates of shoreline recovery occur when Sandbars are closer and attached to the shoreline, observed to be on average 3–4 times greater than for detached Sandbars. In conditions with attached and semi-attached Sandbars, shoreline recovery rates are negatively correlated to the forcing of nearshore wave steepness and dimensionless fall velocity, and coupled with concurrent rates of onshore Sandbar migration. The findings provide insight into key parameters influencing shoreline recovery following storms.
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a behavior oriented dynamic model for Sandbar migration and 2dh evolution
Journal of Geophysical Research, 2011Co-Authors: Kristen D Splinter, Robert A Holman, Nathaniel G PlantAbstract:[1] A nonlinear model is developed to study the time‐dependent relationship between the alongshore variability of a Sandbar, a(t), and alongshore‐averaged Sandbar position, xc(t). Sediment transport equations are derived from energetics‐based formulations. A link between this continuous physical representation and a parametric form describing the migration of Sandbars of constant shape is established through a simple transformation of variables. The model is driven by offshore wave conditions. The parametric equations are dynamically coupled such that changes in one term (i.e., xc) drive changes in the other (i.e., a(t)). The model is tested on 566 days of data from Palm Beach, New South Wales, Australia. Using weighted nonlinear least squares to estimate best fit model coefficients, the model explained 49% and 41% of the variance in measured xc and a(t), respectively. Comparisons against a 1‐D horizontal (1DH) version of the model showed significant improvements when the 2DH terms were included (1DH and 2DH Brier skill scores were −0.12 and 0.42, respectively). Onshore bar migration was not predicted in the 1DH model, while the 2DH model correctly predicted onshore migration in the presence of 2DH morphology and allowed the bar to remain closer to shore for a given amount of breaking, providing an important hysteresis to the system. The model is consistent with observations that active bar migration occurs under breaking waves with onshore migration occurring at timescales of days to weeks and increasing 2DH morphology, while offshore migration occurs rapidly under high waves and coincides with a reduction in 2DH morphology. Citation: Splinter, K. D., R. A. Holman, and N. G. Plant (2011), Abehavior‐orienteddynamicmodelforSandbarmigrationand2DH evolution, J. Geophys. Res., 116, C01020, doi:10.1029/2010JC006382.
Moesker Niek - One of the best experts on this subject based on the ideXlab platform.
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Sandbar breakwaters: Analysis of the effects of variations in wave climate on the morphological development of Sandbar breakwaters by using the Lekki Sandbar Breakwater case study
2020Co-Authors: Moesker NiekAbstract:Many coastlines feature a sediment transport in a dominant direction, possibly burying a traditional breakwater in sand in several years. The Sandbar breakwater concept uses this sediment supply to its benefit to make the use of vast amounts of rocks abundant. During this research the morphological development of the worlds first Sandbar breakwater built in Lekki, Nigeria, is analysed: The minimal amount of sand used for construction of the Lekki breakwater is placed such that the combination of the adaptation of the initialprofile and the natural supply of sediment results in a smooth coastline at the end of the first year. This development is in turn used to setup a calibrated model to study the influence of the wave climate on the development of the Sandbar breakwater concept. The wave climate at Lekki is characterised by a single dominant wave direction (called unidirectional) and has a narrow direction bandwidth (yearly standard deviation of the wave direction is about 5 degrees). This ideal wave climate is altered to research the influence of the mean wave direction, directional variation and the sequence of waves (seasonality). The study showed the Sandbar breakwater concept to be mainly influenced by the mean wave direction and to lesser extent by the directional variation and the seasonality. These results can be used to make a first assessment on the possibility of applying a Sandbar breakwater for a wave climate somewhere around the world.Coastal Engineerin
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Sandbar breakwaters: Analysis of the effects of variations in wave climate on the morphological development of Sandbar breakwaters by using the Lekki Sandbar Breakwater case study
2020Co-Authors: Moesker NiekAbstract:Many coastlines feature a sediment transport in a dominant direction, possibly burying a traditional breakwater in sand in several years. The Sandbar breakwater concept uses this sediment supply to its benefit to make the use of vast amounts of rocks abundant. During this research the morphological development of the worlds first Sandbar breakwater built in Lekki, Nigeria, is analysed: The minimal amount of sand used for construction of the Lekki breakwater is placed such that the combination of the adaptation of the initialprofile and the natural supply of sediment results in a smooth coastline at the end of the first year. This development is in turn used to setup a calibrated model to study the influence of the wave climate on the development of the Sandbar breakwater concept. The wave climate at Lekki is characterised by a single dominant wave direction (called unidirectional) and has a narrow direction bandwidth (yearly standard deviation of the wave direction is about 5 degrees). This ideal wave climate is altered to research the influence of the mean wave direction, directional variation and the sequence of waves (seasonality). The study showed the Sandbar breakwater concept to be mainly influenced by the mean wave direction and to lesser extent by the directional variation and the seasonality. These results can be used to make a first assessment on the possibility of applying a Sandbar breakwater for a wave climate somewhere around the world.Civil Engineering | Hydraulic Engineerin
Rafael Almar - One of the best experts on this subject based on the ideXlab platform.
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two and three dimensional double Sandbar system behaviour under intense wave forcing and a meso macro tidal range
Continental Shelf Research, 2010Co-Authors: Rafael Almar, Bruno Castelle, B G Ruessink, Nadia Senechal, Philippe Bonneton, Vincent MarieuAbstract:Abstract Five weeks of hourly, 10-min time-exposure video images were used to analyze the meso–macro-tidal double-barred Truc Vert Beach, SW France, under intense wave forcing. The four storms experienced, one of which with an offshore significant wave height over 8 m, induced dramatic changes in the double Sandbar system. The subtidal outer bar migrated offshore rapidly (up to 30–50 m/day) and its pre-existing crescentic pattern was wiped out. The seaward-protruding parts of the outer bar barely migrated offshore during the most intense storm, whereas a landward-protruding part was shed off. Over the entire study period, the outer-bar dynamics was dominated by alongshore-averaged changes rather than alongshore non-uniform changes, while the opposite was observed for the inner bar. In addition, the outer-bar dynamics was predominantly controlled by the time-varying offshore wave conditions, whereas the inner-bar dynamics was influenced largely by the tide-range variations. Our observations put forward the key role of morphological settings (the presence of a subtidal bar and its shape) and tidal range in governing inner-bar behaviour within a double Sandbar dynamics, and provide strong support for previous suggestions that Sandbars cannot be studied in isolation.
