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Timber groynes at beach of Eastbourne, East Sussex, UK (top) andmarble beaches at Carrara coast, Italy (bottom)
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The erosional behaviour of gravel type beaches and barriers has been studied using a parametric and a process-based model. Both models have been applied to large-scale laboratory experiments and to a field case at Pevensey Bay, UK. Both models show suprisingly good agreement for realistic wave conditions. The process-based model has been used to co...
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Context 1
... the upper beach consists of gravel/shingle material, while the lower beach or foreshore consists of sandy material, see Figure 2 Top-right. Some of these beaches have a large proportion of sand intermixed with gravel, especially in the foreshore zone just beneath the mean water line (see Figure 2 Top-right). In regimes with dominating gravel populations, the sand becomes a subsidiary interstitial component. In regimes with a relatively large tidal range the back beach may consist of gravel ridges fronted by a low-tide terrace of sand (exposed at low tide). These types of beaches have less appeal for recreational activities, but they are rather efficient (high dissipation of energy through high permeability) for coastal protection. Gravel on beaches is moved almost exclusively by wave action (asymmetric wave motion); tidal or other currents are not effective in moving gravel/shingle material. The coarse particles move up the beach to the run-up limit by strong bores (uprush) and swash motions. The particles move down the beach close to the line of the steepest beach slope by the backwash (less strong due to percolation) plus gravity, resulting in a saw-tooth movement. Waves of long periods on steep beaches can produce peak swash velocities up to 3 m/s. The alongshore transport path of individual clasts (20 to 40 mm) may be as large as 1,000 m per day during periods with storm waves, based on tracer studies. Reviews of swash processes are given by: Van Rijn (2009b), Elfrink and Baldock (2002) and Butt and Russell ...
Context 2
... the upper beach consists of gravel/shingle material, while the lower beach or foreshore consists of sandy material, see Figure 2 Top-right. Some of these beaches have a large proportion of sand intermixed with gravel, especially in the foreshore zone just beneath the mean water line (see Figure 2 Top-right). In regimes with dominating gravel populations, the sand becomes a subsidiary interstitial component. In regimes with a relatively large tidal range the back beach may consist of gravel ridges fronted by a low-tide terrace of sand (exposed at low tide). These types of beaches have less appeal for recreational activities, but they are rather efficient (high dissipation of energy through high permeability) for coastal protection. Gravel on beaches is moved almost exclusively by wave action (asymmetric wave motion); tidal or other currents are not effective in moving gravel/shingle material. The coarse particles move up the beach to the run-up limit by strong bores (uprush) and swash motions. The particles move down the beach close to the line of the steepest beach slope by the backwash (less strong due to percolation) plus gravity, resulting in a saw-tooth movement. Waves of long periods on steep beaches can produce peak swash velocities up to 3 m/s. The alongshore transport path of individual clasts (20 to 40 mm) may be as large as 1,000 m per day during periods with storm waves, based on tracer studies. Reviews of swash processes are given by: Van Rijn (2009b), Elfrink and Baldock (2002) and Butt and Russell ...
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The Weifang artificial beach faces severe erosion at present. The controlling process which induces the sand loss is the continuous westward longshore sediment transport under dominant waves from northeast, as well as the longshore and offshore sediment transport by storm surges. Experimental study in the laboratory was carried out to repeat the cu...
Citations
... Le profil plat du bas des plages de galets est également efficace pour dissiper l'énergie des vagues. Ces sédiments sablo-graveleux sont cependant facilement évacués vers le large par les reflux, et définitivement perdus par la plage du fait de la pente souvent raide des plages sous-marines (Shulmeister & Jennings 1993;Anthony 1997;Van Rijn & Sutherland 2011). ...
Suite à la publication en 2020 d’un premier volume de la Liste rouge des écosystèmes côtiers méditerranéens dédié aux dunes côtières et rivages sableux, le Comité français de l’UICN, l’Office français de la biodiversité (OFB) et le Muséum national d’Histoire naturelle (MNHN) publient un second volume sur les rivages rocheux du littoral méditerranéen. Cette évaluation, qui a mobilisé de nombreux experts (universités, Conservatoires botaniques nationaux, Conservatoire du littoral), montre que deux tiers des écosystèmes identifiés sont menacés ou quasi-menacés du fait de l’urbanisation du littoral, de la fréquentation ou encore de la présence d’espèces végétales exotiques envahissantes. Des actions sont nécessaires pour protéger ce patrimoine écologique exceptionnel, avec des cortèges d’espèces que l’on ne retrouve nulle part ailleurs en France.
... The EUROSION concepts were applied to the Conscience Project, which also includes the sediment reservoirs on the sediment cell that can act as a source of sediment (Van Rijn, 2010). These aspects are also discussed in the Micore Project, which stressed the application of nourishment projects to contrast climate change effects, in particular extreme storms and the sea level rise (Ciavola et al., 2011). ...
... The continental shelf is sediment-starved, with limited land-to-sea sedimentary run-off. The transgressive deposits associated with the last sea level rise are characterised by siliciclastic sands and calcareous bioclastic sands (Carboni et al., 1989;De Falco et al., 2008, 2010) along the inner shelf as well as clays and calcareous mud along the outer shelf (Carboni et al., 1989). ...
The expected global sea level rise by the year 2100 will determine adaptation of the whole coastal system and the land retreat of the shoreline. Future scenarios coupled with the improvement of mining technologies will favour increased exploitation of sand deposits for nourishment, especially for urban beaches and sandy coasts with lowlands behind them. The objective of the work is to provide useful tools to support planning in the management of sand deposits located on the continental shelf of Western Sardinia (western Mediterranean Sea). The work has been realised through the integration of data and information collected during several projects. Available data consist of morpho-bathymetric data (multibeam) associated with morphoacoustic (backscatter) data, collected in the depth range −25 to −700 m. Extensive coverage of high-resolution seismic profiles (Chirp 3.5 kHz) has been acquired along the continental shelf. Also, surface sediment samples (Van Veen grab and box corer) and vibrocorers have been collected. These data allow mapping of the submerged sand deposits with the determination of their thickness and volume and their sedimentological characteristics. Furthermore, it is possible to map the seabed geomorphological features of the continental shelf of Western Sardinia. All the available data (https://doi.org/10.1594/PANGAEA.895430) have been integrated and organised in a geodatabase implemented through a GIS and the software suite Geoinformation Enabling ToolkIT StarterKit® (GET-IT), developed by researchers of the Italian National Research Council for RITMARE project. GET-IT facilitates the creation of distributed nodes of an interoperable spatial data infrastructure (SDI) and enables unskilled researchers from various scientific domains to create their own Open Geospatial Consortium (OGC) standard services for distributing geospatial data, observations and metadata of sensors and data sets.
Data distribution through standard services follows the guidelines of the European Directive INSPIRE (DIRECTIVE 2007/2/EC); in particular, standard metadata describe each map level, containing identifiers such as data type, origin, property, quality, processing processes to foster data searching and quality assessment.
... The swash zone is the most dynamic part of the nearshore zone, where pebbles are moved by wave action (asymmetric wave motion e.g., Elfrink and Baldock, 2002), thus providing an effective "mill" for plastics. On natural beaches, a swash zone is a zone which is intermittently wet and dry showing relatively large velocities (up to 3 m/s for long waves on steep beaches Van Rijn, 2013) during the uprush and backwash phases of the saw-tooth swash wave cycle due to bore propagation and bore collapse (Van Rijn, 2013). The pebbles are moved up the beach to the run-up limit by strong bores (uprush) and moved down the beach close to the line of the steepest beach slope by the backwash (less strong due to percolation) plus gravity, resulting in a sawtooth movement (Van Rijn, 2013). ...
... On natural beaches, a swash zone is a zone which is intermittently wet and dry showing relatively large velocities (up to 3 m/s for long waves on steep beaches Van Rijn, 2013) during the uprush and backwash phases of the saw-tooth swash wave cycle due to bore propagation and bore collapse (Van Rijn, 2013). The pebbles are moved up the beach to the run-up limit by strong bores (uprush) and moved down the beach close to the line of the steepest beach slope by the backwash (less strong due to percolation) plus gravity, resulting in a sawtooth movement (Van Rijn, 2013). In order to reproduce the main features of this process in a laboratory, we modified the standard concrete mixer, removing the metallic blades and adjusting the angle of inclination of the axis as described below. ...
Marine beaches worldwide are nowadays exposed to significant contamination by plastics. On the Baltic beaches, polyethylene, polypropylene, and polystyrene are most abundant. We investigate the generation of microplastics particles (MPs, characteristic size from 0.5 to 5 mm) from larger plastic items in the sea swash zone using a laboratory rotating mixer filled with water and natural coarse beach sediment (marine pebbles). Inclination of the axis of rotation and the volume of the material were adjusted in such a way that mixing resembled a breaking wave in the swash zone. Plastic samples used were of the types most commonly found on the sea beaches. Experimental 2 × 2 cm-large plastic items made of low-density polyethylene (LDPE) were manufactured from common new garbage bags (thickness 5 µm); those made of polypropylene (PP) and polystyrene (PS) were produced from single-use tableware; samples of foamed plastics were presented by cubes (with 2-cm sides) cut out of standard building insulator sheets (foamed PS). Four sets of 24-h-long experiments were conducted (for each type of plastic separately), with step-wise (every 3 h) examination of the generated MPs mass, number of particles, and their qualitative characteristics such as shape, quality of the surface, general behavior while mixing, etc. Statistically significant dependencies are obtained for the increase in mass and in number of MPs with time for all four used kinds of plastics. Brittle solid PS is shown to be the most productive in terms of both mass and number of MPs generated. Anisotropic springing PP is the most resistant. Tensile tearing of LDPE and fragmentation of foamed PS to compounding bubbles/spherules show the variety of mechanisms involved in fragmentation of plastics in the swash zone. Increase in MPs mass and the number of MPs particles with time, as well the link between them, are important for field monitoring and numerical modeling. Potentially shape-selective operation of sieves during sampling and sorting of MPs particles of various shapes is discussed.
... This discrepancy is particularly evident for numerical approaches ( Orford and Anthony, 2011;Masselink et al., 2014), and contrasts strongly with the increasing demand for reliable coastal change models to help mitigate and adapt to global erosion problems ( Syvitski et al., 2005;Anthony et al., 2014) and future sea-level rise ( Payo et al., 2016;Spencer et al., 2016). Several efforts have been made over the last decade to develop a morphodynamic storm response model specific to gravel beaches ( Pedrozo-Acu~ na, 2005;Pedrozo-Acu~ na et al., 2006Van Rijn and Sutherland, 2011;Jamal et al., 2011Jamal et al., , 2014Williams et al., 2012). In the present paper, we use the XBeach-G model ( McCall et al., 2012McCall et al., , 2013McCall, 2015), as it has been validated most extensively using both laboratory and field data ( McCall et al., 2014McCall et al., , 2015Almeida et al., 2017). ...
This paper investigates the profile response of a mixed sand-gravel deltaic beach (Playa Granada, southern Spain) forced by storm waves from varying directions. Beach morphology was monitored over a 36-day period with variable wave conditions, and profile response was compared to model predictions using the XBeach-G model and a longshore sediment transport (LST) formulation. XBeach-G was applied over 2-day periods of low energy, south-westerly (SW) storm and south-easterly (SE) storm conditions, and was coupled to LST using a parametric approach which distributes the LST across the swash, surf and nearshore zones. A calibrated wave propagation model (Delft3D) was used to obtain the inshore conditions required to drive the XBeach-G model and the LST formulation. The storm response is clearly influenced by the free-board (difference between the height of the berm and the total run-up) and is also strongly dependent on storm-wave direction, with the SW storm eroding the surveyed area, while the SE storm induced beach accretion. Model results indicate that XBeach-G on its own is capable of adequately reproducing the response of the beach under SW storm conditions (BSS>0.95), but not under SE storms due to the higher LST gradients at the study location. The combination of XBeach-G and LST fits the measured profiles reasonably well under both SW (BSS>0.96) and SE (BSS>0.88) storms, inspiring confidence in the coupled model to predict the storm response under varying wave conditions. The combined XBeach-G/LST model was applied to the entire 6.8-km deltaic coastline to investigate the impact of extreme SW and SE storm events, and the model results reiterate the importance of cross-shore and longshore sediment transport in driving coastal storm response at this location. The approach proposed in this work can be extended to other worldwide coasts highly influenced by both cross-shore and longshore sediment transport, such as beaches with different coastline orientations and/or forced by varying wave directions.
... In this context, several efforts have been made over last decade to develop a storm response model specific to gravel beaches (Pedrozo-Acuña, 2005;Pedrozo-Acuna et al., 2006;Pedrozo-Acuña et al., 2007;Van Rijn and Sutherland, 2011;Jamal et al., 2011Jamal et al., , 2014Williams et al., 2012), resulting in the implementation of a process-based model (XBeach-G) for the prediction of storm hydro-and morphodynamics of the beach profile McCall, 2015). The model has been extensively validated on cross-shore dominated gravel beaches ; however, it has not been tested on MSG coasts. ...
This work aims to calibrate the XBeach-G model on a mixed sand-gravel deltaic coast (Playa Granada, southern Spain) and apply it to address the overwash vulnerability. Field surveys, consisting of topographical measurements and sediment sampling in two selected areas, were performed before and after two extreme southwesterly storms. A calibrated wave propagation model (Delft3D-WAVE) was used to obtain the inshore conditions required to drive the XBeach-G model. The XBeach-G results for the coarse gravel fraction, a sediment friction factor of 0.03 and a Nielsen's boundary layer phase lag of 20º were found to provide the best fits to the observed morphological changes of the beach profile. This indicates that the morphodynamic response of the beach is dominated by the coarse gravel fraction, which is in agreement with previous experimental and numerical works carried out in the study site. The obtained brier skill scores and root-mean-square errors were higher than 0.89 and lower than 0.18 m, respectively, highlighting that the XBeach-G model is capable of reproducing the profile response under southwesterly storm conditions. The model was used to compute the required water level to generate overwash as a function of the wave height and direction, and results show how the application of XBeach-G can be used to address issues of storm-induced coastal vulnerability on gravel-dominated coasts.
... Modified from Orford et al. (2003) and Donnelly (2007). Sutherland, 2011). Furthermore, since these empirical models have been developed using data from idealised laboratory studies, managed and non-uniform coastlines containing for instance man-made flood defence and beach regulation structures cannot easily be simulated using such models. ...
... While these models in themselves may be considered a step forward relative to empirical models, they may not accurately represent the physics occurring during energetic storm events. Furthermore, due to lack of physical processes such as infiltration (Pedrozo-Acuña et al., 2007;Van Rijn and Sutherland, 2011) and incident band swash dynamics (Jamal et al., 2014;Van Rijn and Sutherland, 2011;Williams et al., 2012b), the ability of these models to accurately predict morphological change depends on the use of artificial, and potentially site and condition-specific, coefficients to adjust important physical processes (e.g., uprush to downwash sediment transport ratio, swash zone velocities, wave run-up levels). ...
... While these models in themselves may be considered a step forward relative to empirical models, they may not accurately represent the physics occurring during energetic storm events. Furthermore, due to lack of physical processes such as infiltration (Pedrozo-Acuña et al., 2007;Van Rijn and Sutherland, 2011) and incident band swash dynamics (Jamal et al., 2014;Van Rijn and Sutherland, 2011;Williams et al., 2012b), the ability of these models to accurately predict morphological change depends on the use of artificial, and potentially site and condition-specific, coefficients to adjust important physical processes (e.g., uprush to downwash sediment transport ratio, swash zone velocities, wave run-up levels). ...
This paper presents an extension of the XBeach-G numerical model with a sediment transport and morphology module, which includes the effect of groundwater ventilation and flow inertia on sediment transport, to simulate the morphodynamic response of pure gravel beaches and barriers to storms. The morphodynamic XBeach-G model is validated by simulating the morphodynamic response of one laboratory and four natural gravel barriers to 10 separate storm events, where the observed morphodynamic response ranged from berm building to barrier rollover. Model results show that XBeach-G is capable of reproducing the type of morphodynamic response of the barrier well in qualitative and quantitative sense (median BSS 0.75), with higher skill for more energetic storm conditions. Inclusion of acceleration forces on coarse gravel beaches is shown to significantly increase model skill and may be essential in modelling these types of beaches. The effect of varying hydraulic conductivity within estimated and published ranges is shown to be of secondary importance. The range of validation cases and lack of site-specific calibration show that XBeach-G can be applied to predict storm impacts on pure gravel beaches and barriers with reasonable to high confidence for a range of hydrodynamic forcing conditions and barrier response types.
... In contrast, relatively few processbased models have been developed for gravel beaches. Due to the lack of measurement data collected under energetic to storm conditions on gravel beaches, existing process-based morphodynamic models for gravel beaches (e.g., Jamal et al., 2014;Pedrozo-Acuña et al., 2006;Van Rijn and Sutherland, 2011;Williams et al., 2012b) have been developed using data collected on natural or laboratory gravel beaches during low to moderate wave energy conditions, and may therefore not be representative of the physics and morphodynamics occurring during energetic storm events. ...
In this paper we present a process-based numerical model for the prediction of storm hydrodynamics and hydrology on gravel beaches. The model comprises an extension of an existing open-source storm-impact model for sandy coasts (XBeach), through the application of (1) a non-hydrostatic pressure correction term that allows wave-by-wave modelling of the surface elevation and depth-averaged flow, and (2) a groundwater model that allows infiltration and exfiltration through the permeable gravel bed to be simulated, and is referred to as XBeach-G. Although the model contains validated sediment transport relations for sandy environments, transport relations for gravel in the model are currently under development and unvalidated. Consequently, all simulations in this paper are carried out without morphodynamic feedback. Modelled hydrodynamics are validated using data collected during a large-scale physical model experiment and detailed in-situ field data collected at Loe Bar, Cornwall, UK, as well as remote-sensed data collected at four gravel beach locations along the UK coast during the 2012–2013 storm season. Validation results show that the model has good skill in predicting wave transformation (overall SCI 0.14–0.21), run-up levels (SCI < 0.12; median error < 10%) and initial wave overtopping (85–90% prediction rate at barrier crest), indicating that the model can be applied to estimate potential storm impact on gravel beaches. The inclusion of the non-hydrostatic pressure correction term and groundwater model is shown to significantly improve the prediction and evolution of overtopping events.
Small plastic particles (microplastics, < 5 mm) are found in the World Ocean everywhere, from the surface to the bottom, from the ice of the Arctic to the waters of the Antarctic. Their properties differ from the properties of natural particles and at the same time change noticeably with time in the environment, so the description of the transfer of microplastics in the ocean and the patterns of its accumulation require additional, targeted, and deeply interdisciplinary efforts.
This book touches on only a small part of the issues on which some understanding has been achieved so far. Moreover, due to the scientific specialization of the authors, the clear preference is given to the problems of physical oceanography. According to the logic of presentation, the material is divided into five parts: from general questions and a review of publications - through analytical models and a laboratory experiment - to field observations and research methods.
The Introduction and Part I provide an overview of the general information on the problem of plastic pollution in the oceans. Potential threats to the environment and humans are discussed. Basic information about plastic as a material is given. Chapters 2 and 3 summarize information about the properties of microplastic particles actually observed in the marine environment, as well as the mechanisms for changing these properties over time.
Part II presents simple analytical models for describing the properties of microplastic particles. They include both simple balance and geometric models of a single particle (Chapter 4) and options for taking into account distributions of particle properties in terms of size, shape, and density (Chapter 5). Chapter 6 presents the results of modeling the probabilistic distribution of the terminal settling/rising velocity of microplastic particles, obtained on the basis of distributions of particle properties by size, density, and shape.
Part III is devoted to the results of laboratory experiments. Settling of microplastic particles of various forms, including synthetic fibers, is described (Chapter 7). The approaches and available experimental data on the resuspension of microplastic particles of various shapes from the bottom covered with natural sediment are discussed (Chapter 8). The results of a series of experiments on the fragmentation of various types of plastic in the surf zone are presented in detail (Chapter 9).
Field observations of microplastic and marine debris pollution in the Baltic Sea region – on its beaches, in the water column, and bottom sediments – are presented in Part IV.
Part V summarizes information on current sampling methods for microplastics in water, bottom sediment, and beach sediments, sample preparation techniques, extraction steps, and identification methods. The requirements for the control of external pollution, options for presenting the results in various units, and other "little things" that determine the quality of the final result and the possibility of its comparison with other studies are given.
The book is intended for ocean scientists, as well as undergraduate and graduate students of relevant specialties, but it will also be useful to the widest range of readers, showing the incredible vulnerability of the natural environment of our small planet.
The authors express their sincere gratitude to the colleagues with whom the results presented in the book were obtained and published: Dr. Andrey Bagaev and Dr. Artem Mizyuk (Marine Hydrophysical Institute, Russian Academy of Sciences), Dr. Mikhail Zobkov (Northern Water Problems Institute, Karelian Research Center of the RAS), Dr. Andrey Zyubin (Immanuel Kant Baltic Federal University), Irina Efimova, Anastasiya Kupriyanova, as well as to many colleagues who participated in expeditions and sample processing. Great help in preparing the manuscript for publication was provided by Nataliya Martynyuk.
The book represents some results obtained by the authors while working on projects of the Russian Science Foundation (15-17-10020, 19-17-00041), Russian Foundation for Basic Research (18-55-76001, 18-55-76002, 18-35-00553, 19-35-50028; 19-45-393006), the Swedish Institute project 22805/2019 (MOTION), and within SCOR WG 153 (FLOTSAM).
Desde 2016 o Brasil possui um Plano Nacional de Adaptação à Mudança do Clima (PNA). Elaborado pelo Ministério do Meio Ambiente (Brasil, 2016), tal plano busca promover a redução da vulnerabilidade nacional à mudança do clima e a realização de uma gestão do risco associado a esse fenômeno. Tal Plano dá especial atenção às zonas costeiras do país. No Estado do Rio Grande do Sul (RS), a Zona Costeira está sujeita ao impacto de eventos meteorológicos energéticos durante os períodos de outono e inverno. Ressacas do mar e enchentes marinhas são comuns durante e após a passagem desses eventos, colocando pessoas, infraestruturas e ecossistemas em risco. As dunas frontais constituem a primeira linha de defesa natural do continente frente às inundações marinhas e à erosão costeira. Sendo assim, o presente estudo aplica o modelo da Regra de Erosão de Dunas a fim de quantificar a erosão de dunas frontais em uma praia no litoral sul do Rio Grande do Sul (RS). Tal aplicação busca validar este modelo para as praias do RS. A caracterização dos processos erosivos foi realizada com base na Escala de Impacto de Tempestades, categorizando os eventos analisados dentro de quatro categorias. O modelo de erosão de dunas apresentou valores altos de erosão devido às configurações dos parâmetros do modelo, os quais devem ser adaptados para o litoral do RS para melhor aplicabilidade. A aplicação conjugada destes dois modelos tem relevante potencial para uso direto na gestão dos ecossistemas costeiros, visto que, após devidamente adaptados à escala local, inferem as dimensões e características necessárias para que as dunas frontais possam efetivamente cumprir sua função de proteção costeira.
Coastal erosion is a problem at many coastal sites caused by natural effects as well as human activities. This paper explores the coastal cell concept to deal with coastal erosion by identifying and analysingthe sediment volumes accumulated in large-scale and small-scale coastal cells at various sites. Mechanisms causing chronic erosion and episodic erosion related to coastal variability are identified and discussed. The effectiveness of soft and hard remedial measures for sandy beaches are assessed based on laboratory, field and modelling experiences.
