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Celia storm was an intense event that hit the NW Mediterranean Spanish coast during March 2022. During those dates a study was conducted where 2 instrumented platforms were installed, together with the gathering of high-resolution topobathymetric information at the Sant Sebastià and Sant Miquel beaches (Barcelona). The information taken from this campaign helped to calibrate and validate separately the hydrodynamics of the models XBeach and COAWST. A nesting strategy was done between these models in order to improve the validation of XBeach hydrodynamics. The approach is designed for a pass from a pre-operational to an operational framework in the future.The aim of the study is to integrate both models within a reasonable computational time and good accuracy which will help to forecast possible flooding and erosion hazards and consequently create an Early Warning System in the area. The full strategy comprises atmospheric and hydrodynamic forcings from CMEMS into COAWST that feed the hydrodynamic conditions of XBeach. The simulations were done using the MPI modules of the models to reduce the computational expense and the post-processing using Python/Matlab.Results from the validation of the models will be presented as well as the inundation and the erosion derived from the storm impact at the area. Also, some methodologies that could be applied for validate both outputs will be discussed.Funding: This project has received funding from the European Union’s Horizon 2020 research and innovation programme under grant agreement No 101037097 (REST-COAST project).Acknowledgments: The first author has the support of the Secretariat for Universities and Research of the Ministry of Business and Knowledge of the Government of Catalonia and the European Social Fund.

Onshore bar migration is a characteristic bar behavior during post-storm beach recovery. The present large-scale experiments, feature bichromatic wave groups over an initially steep (1:15), fully-evolving beach. The same accretive wave condition is applied on two different post-storm beach profiles featuring outer and inner bars. They are characterized by a larger (smaller) shoreline erosion and a larger (smaller) outer breaker bar located farther away from (closer to) the shoreline depending on the larger (smaller) energy of the storm condition. After a considerable post-storm recovery time, similar equilibrium profiles are obtained, stressing the link between wave condition and equilibrium beach configuration. However, the evolution toward the equilibrium is different and depends on the initial morphological condition (post-storm beach profile). After the larger storm, the morphological evolution is termed accretive merging (AM) and characterized by merging of the two bars (outer bar dissipation). After the smaller storm, the morphological evolution denoted as accretive non-merging (AN) is characterized by onshore migration of the two bars with constant distance between them (bar maintenance). This study focuses on processes around the outer bar. During AN it features wave breaking, causing large suspended net offshore transport. AM, in contrast, mainly features bedload related to short wave asymmetries and low decomposed net transport rate magnitudes. High suspended net offshore transport occurs solely onshore of the outer bar trough. This causes filling of the bar trough and bar dissipation during migration. Additionally, processes around the outer bars are linked to accretion onshore of the bars and at the shoreline. We thank Dr. Tom Baldock and Dr. Marissa Yates for their valuable comments which helped to improve the manuscript. The experiments described in this work were funded by the European Community's Horizon 2020 Programme through the grant to the budget of the Integrated Infrastructure Initiative HYDRALAB+, Contract no. 654110, and were conducted as part of the transnational access project RESIST. FG acknowledges funding from the Agency for Management of University and Research Grants (AGAUR). DH acknowledges funding from the French DGA funded ANR ASTRID Maturation project MESURE (ANR-16-ASMA-0005-01). JA acknowledges funding from the Serra Húnter Programme (SHP). We wish to thank fellow RESIST researchers and the CIEM staff (Joaquim Sospedra, Oscar Galego, Dr. Andrea Marzeddu and Dr. Iván Cáceres) for their contributions to the experiments.

Detailed information on nearshore sediment transport processes during onshore bar migration were obtained from large-scale laboratory experiments with bichromatic wave groups on a relatively steep initial beach slope (1:15). Detailed measurements of velocity and sand concentration near the bed from shoaling up to the outer breaking zone including suspended sediment and sheet flow transport are presented. The analysis focuses on onshore migration under an accretive wave condition but comparison to an erosive condition highlights important differences. Decomposition shows that total transport mainly results from a balance of short wave-related, bedload onshore transport and current-related, suspended offshore transport. When comparing the accretive to the more energetic erosive condition, the balance shifts toward onshore transport, and onshore migration, because the short wave-related transport does not decrease as much as the current-related transport. This is related to the effects of skewness and asymmetry combined with less sediment suspension in the water column and undertow magnitude under the accretive condition. Transports from streaming in the wave boundary layer and from infragravity waves become visible but only play a subordinate role. Identified priorities for numerical model development include parametrization of wave nonlinearity effects and better description of wave breaking and its influences on sediment suspension. We thank Dr. Troels Aagaard and another, anonymous reviewer for their valuable comments which helped to improve the manuscript. The experiments described in this work were funded by the European Community's Horizon 2020 Programme through the grant to the budget of the Integrated Infrastructure Initiative HYDRALAB+, Contract 654110, and were conducted as part of the transnational access project RESIST. FG acknowledges funding from the Agency for Management of University and Research Grants (AGAUR). DH acknowledges funding from the French DGA funded ANR ASTRID Maturation project MESURE (ANR-16-ASMA-0005-01). JA acknowledges funding from the Serra Húnter Programme (SHP). We wish to thank fellow RESIST researchers and the CIEM staff (Joaquim Sospedra, Oscar Galego, Dr. Andrea Marzeddu, and Dr. Iván Cáceres) for their contributions to the experiments.

Onshore bar migration is a characteristic bar behavior during post-storm beach recovery. The present large-scale experiments, feature bichromatic wave groups over an initially steep (1:15), fully-evolving beach. The same accretive wave condition is applied on two different post-storm beach profiles featuring outer and inner bars. They are characterized by a larger (smaller) shoreline erosion and a larger (smaller) outer breaker bar located farther away from (closer to) the shoreline depending on the larger (smaller) energy of the storm condition. After a considerable post-storm recovery time, similar equilibrium profiles are obtained, stressing the link between wave condition and equilibrium beach configuration. However, the evolution towards the equilibrium is different and depends on the initial morphological condition (post-storm beach profile). After the larger storm, the morphological evolution is termed AM and characterized by merging of the two bars (outer bar dissipation). After the smaller storm, the morphological evolution denoted as AN is characterized by onshore migration of the two bars with constant distance between them (bar maintenance). This study focuses on processes around the outer bar. During AN it features wave breaking, causing large suspended net offshore transport. AM, in contrast, mainly features bedload related to short wave asymmetries and low decomposed net transport rate magnitudes. High suspended net offshore transport occurs solely onshore of the outer bar trough. This causes filling of the bar trough and bar dissipation during migration. Additionally, processes around the outer bars are linked to accretion onshore of the bars and at the shoreline. About the data: The folder “Beach Profiles” contains the measurements from the mechanical profiler before and after each test. To save time, only the morphologically active section of the profiles was measured. Additionally, the folder contains the initial profiles at the start of each sequence (after application of the benchmark waves). Here the full profile was measured. The structure “MobFrame” contains the absolute cross-shore position of the mobile frame (from which detailed measurements were taken) in the considered tests. The folder “ACVP” contains structures with ensemble-averaged velocity and concentration measurements in vertical reference to the undisturbed bed level or a few bins below it (zeta0-coordinate system as described in the paper). For better interpretation of the measurements, it also features the ensemble-averaged intrawave instantaneous bed elevation (erosion depth) and the upper limit of the sheet flow layer. The folder “ADV” contains structures with the ensemble-averaged ADV data of each test. Apart from the velocity components of each ADV they contain the vertical elevation of each ADV with respect to the ACVP transceiver. The ADV measurements were not subject to the same vertical referencing procedure that was described in the paper for the near-bed ACVP measurements. The folder “OBS” contains structures with the ensemble-averaged OBS data of each test. Apart from the concentration measurements in each OBS sensor they contain the vertical elevation of each OBS with respect to the ACVP transceiver. The folder “ETA” contains structures with the ensemble-averaged surface elevation data of each test (from different instruments as described in the paper). The location of each instrument is given in absolute cross-shore coordinates x. For visualizing the near-bed concentration data, which may not be as trivial as visualizing the rest of the data, an example of MATLAB code is given: %S=ACVP_xx; %to choose which ACVP file you want to look into con=S.c; con(con xphase=linspace(0,1,length(S.solbed)).*ones(size(S.c,2),size(S.c,1)); figure; hold on; box on; [C,h]=contourf(xphase,S.z,log10(transpose(con)),[0:0.1:3]); cbh=colorbar; caxis([0 3]); set(h,'edgecolor','none'); tt=get(cbh,'Title'); set(tt,'String','$log_{10}(c)$ $[kg/m^3]$','Interpreter','Latex'); plot(xphase(1,:),S.solbed,'k','Linewidth',1.5); plot(xphase(1,:),S.solflo,'r','Linewidth',1.5); xlabel('$t/T_r$','Interpreter','Latex') ylabel('$\zeta_0$ $[m]$','Interpreter','Latex') set(gca,'Fontsize',18)

New flume experiments with surrogate seagrass meadows are presented. The experiments included the creation of a full-scale and realistic Posidonia Oceanica model to evaluate the effect over wave attenuation, sediment transport and shoreline erosion. A hydrodynamic and morphodynamic comparison between cases with seagrass and without seagrass for two wave energy conditions was performed. Meadow density and submergence ratio were constant for tests under irregular waves. The wave height reduction, bar crest location, total sediment transport and shoreline position were used to evaluate the coastal protection efficiency of the meadow. The measured wave heights suffered a reduction due to the presence of the seagrass. These reductions were persistent in the area located between the onshore edge of the meadow and the depth of closure, being of greater magnitude in the more energetic case. All tests showed the development of a bar and the migration of the crest offshore over time. However, the dissipation of the incoming wave energy on the meadow made the bar crest stay closer to the shoreline and consequently generated a lower freeboard. In addition, the bar migration rate was reduced by the simulated meadow effect, in particular in the lower energetic case. A sediment volume significantly smaller was transported offshore when the seagrass meadow was present in both wave conditions. Additionally, in the higher energy case, a smaller shoreline retreat was observed when the meadow was present. The experiments described in this work were funded by the Spanish Government within the Research, Development and Innovation Program through the grant to COBALTO project (Ref. CTM2017-88036-R). The support of the Secretaria d'Universitats i Recerca del Departament d'Economia i Coneixement de la Generalitat de Catalunya (Ref. 2014SGR1253) is also acknowledged. The first author acknowledges funding from the National Agency for Research and Development (ANID)/Scholarship Program/DOCTORADO BECAS CHILE/2018–72190552. We wish to thank the technical staff of the CIEM wave flume (UPC) for their support and contributions to the experiments: Joaquim Sospedra, Oscar Galego and Ricardo Torres.

This study presents novel insights into hydrodynamics and sediment fluxes in large-scale laboratory experiments with bichromatic wave groups on a relatively steep initial beach slope (1:15). An Acoustic Concentration and Velocity Profiler provided detailed information of velocity and sand concentration near the bed from shoaling up to the outer breaking zone including suspended sediment and sheet flow transport. The morphological evolution was characterized by offshore migration of the outer breaker bar. Decomposition of the total net transport revealed a balance of onshore-directed, short wave-related and offshore-directed, current-related net transport. The short wave-related transport mainly occurred as bedload over small vertical extents. It was linked to characteristic intrawave sheet flow layer expansions during short wave crests. The current-related transport rate featured lower maximum flux magnitudes but occurred over larger vertical extents. As a result, it was larger than the short wave-related transport rate in all but one cross-shore position, driving the bar’s offshore migration. Net flux magnitudes of the infragravity component were comparatively low but played a nonnegligible role for total net transport rate in certain cross-shore positions. Net infragravity flux profiles sometimes featured opposing directions over the vertical. The fluxes were linked to a standing infragravity wave pattern and to the correlation of the short wave envelope, controlling suspension, with the infragravity wave velocity. The experiments described in this study were funded by the European Community’s Horizon 2020 Program through the grant to the budget of the Integrated Infrastructure Initiative HYDRALAB+, Contract no. 654110, and were conducted as part of the transnational access project RESIST. FG acknowledges funding from the Agency for Management of University and Research Grants (AGAUR). DH acknowledges funding from the French DGA funded ANR ASTRID Maturation project MESURE (ANR-16-ASMA-0005-01). JA acknowledges funding from the Serra Húnter Program (SHP). The authors wish to thank fellow RESIST researchers and the CIEM staff (Joaquim Sospedra, Oscar Galego, Dr. Andrea Marzeddu) for their contributions to the experiments.

Hydromorphodynamic modelling has as one of its pillars the speed of obtaining results. Sometimes it is only due to the necessity to finish some work or to make other simulations but for example when talking about operational systems, this problematic takes even more strength. If other coastal operational modelling have to be coupled after, the model itself has to be fed by other models or the results have to be published periodically, the importance of the simulation speed is clear. A problem appears because there is an insoluble paradigm which doesn’t allow to make simulations combining the best approaches for this three variables: low ”computational time”, high ”resolution” and huge ”study area”. For example, if we want to simulate a huge coastal area but we need to present the results as soon as possible (i.e. low computational time), we will not be able to use a high-resolution grid because it will fail in the second statement. This problem appears in all the other possible scenarios involving this three variables where the best response for all of them cannot be satisfied at the same time due to the paradigm. Then, since it is impossible to totally solve this problematic, a lot of efforts have been made to reduce its effects and to work with the best possible approaches. In this work, two methodologies that try to improve the performance of the hydromorphodynamic simulations with XBeach model are tested and statically compared with the typical performance. On one hand, a direct reduction of the computational time using parallel computing, specifically Message Passing Interface (MPI) with Cluster application. On the other hand, the conversion of the grids that are used for the simulation from rectangular to curvilinear in order to increase only the resolution of the area of interest in the grid, maintaining lower resolutions for the rest of the area.This research received funding from INTERREG EFA 344/19 MARLIT Project European Union / European Regional Development Fund thanks (FEDER) and was done with the support from the Secretariat for Universities and Research of the Ministry of Business and Knowledge of the Government of Catalonia and the European Social Fund. We also want to thank the Research, Development and Innovation Program through the grant to ECOPLANTS project (REF: PID2020-119058RB-I00).

Quality ocean information from observations and forecasting is crucial to support evidence-based decision making and providing a crucial framework for underpinning the scientific basis for policies that regulate the use of the oceans, coastal regions and port areas, maintaining their healthy ecosystems, protecting the development of the littoral zones, and monitoring the environmental mitigation efforts. However, there are fundamental gaps in our ocean observing and forecasting capabilities, limiting our capacity to manage the oceans, coastal regions, and port areas sustainably. Therefore, particularly for coastal areas, it is necessary to ensure high-level integration for coordinated observations that can be sustained in the long term and help to improve ocean forecasting to ensure safe and sustainable human-coastal interaction.The EuroSea initiative [1] is an innovative action of the European Union that brings together key European actors in ocean observation and forecasting with key European end-users in ocean observation, thereby promoting a genuinely interdisciplinary ocean observing system and providing oceanographic products and services. Furthermore, it enables high-resolution coastal operations and forecasting systems in restricted domains such as local ports, beaches, and nearby coastal waters. The EuroSea Project aims to advance scientific knowledge about ocean climate, marine ecosystems, and their vulnerability to human impacts and demonstrate the ocean's importance for a healthy and economically viable society.Within the EuroSea project framework, we present a 3D hydrodynamic tool to improve the sustainable management of Barcelona's local coastal waters. We use the Coupled Ocean-Atmosphere-Wave-Sediment Transport Modeling System [2] that utilises the Model Coupling Toolkit to exchange prognostic variables between the circulation model ROMS and the wave model SWAN. As part of the system, the wave and circulation models run with nested and refined grids to provide increased spatial resolution, scaling down to solve nearshore wave-driven flows, all within selected regions of a larger, coarser-scale coastal modelling system. Bathymetry was built using a combination of data from EMODnet [3] and specific high-resolution sources provided by local authorities. Copernicus products have driven these high-resolution simulations.Field campaigns have been used to validate results, displaying agreements between modelled outputs and in-situ observations. Therefore, the model provides results that will be used to develop new forecast capabilities, such as predicting erosion and flooding, simulating rip currents, tracking the floating debris, and knowing the flushing times.Finally, we look ahead to the future of the development and maintenance of the operational prediction systems because their harmonisation and integration with the existing ocean knowledge will increase the availability of credible scientific evidence to inform industry, help to reduce the impact of human activities on the ocean and improve environmental management. We would like to acknowledge financial support from EuroSea Project (GA862626), an EU Innovation Action funded through Horizon 2020. [1] EuroSea Project (https://eurosea.eu/)[2] Warner, J.C., Armstrong, B., He, R., and Zambon, J.B., 2010, Development of a Coupled Ocean-Atmosphere-Wave-Sediment Transport (COAWST) modelling system: Ocean Modeling, v. 35, no. 3, p. 230-244.[3] EMODnet (https://www.emodnet-bathymetry.eu/)

The cruise industry has evolved rapidly over the past decades, with the building and operation of ever-larger cruise ships being a key factor in this growth. This study examines whether the observed increases in vessel size are supported by the fundamentals of economies of scale, as allegedly occurs with container ships; in other words, we inquire whether increases in ship size imply decreases in the average costs per passenger. We attempt this by developing a detailed cost model for cruise ships, distinguishing among three types of costs: capital costs, operating costs and voyage costs. The quantification of these costs allows the determination of potential savings due to the presence of scale. In parallel, we analyse the sensitivity of each cost category to parameters such as sailing speed and distance travelled. The research provides an assessment of the direction the cruise industry is heading, as regards the scale of vessels in operation: our findings suggest that economies of scale are realised only up to a certain ship size, which today stands at 120,000 gross tons. For larger cruise vessels, average costs (per passenger) increase and dis-economies of scale start to set in.

The present study aims at computing and analysing the eroded sediment volumes induced by twin-propeller jets near a vertical quay wall from the main geometric characteristics of the scour hole. Two different scouring mechanisms govern the scouring process: i) the down-flow due to the interaction between the propellers jet and the wall, and ii) the direct impact of the propellers jet flow on the seabed. For this reason, the whole study area is divided into two subzones: 1) ’near the wall’ field; 2) ’far from the wall’ field. Both forward and backward rotation of the propellers during manoeuvring are analysed. The results show that, for the two manoeuvring states, the relationship between the eroded volume and the geometric characteristics of the scour hole in the near-wall subzone does not change, meaning that the backward rotation does not affect the morphology of the scour hole near the wall. Moreover, the eroded volume can be determined as a function of the maximum depth near the wall and, with higher accuracy, as a product of the three main geometric characteristics of the scour hole at any time-stage during the scour hole development

Phytoplankton primary production in coastal bays and estuaries is influenced by multiple physical variables, such as wind, tides, freshwater inputs or light availability. In a short-term perspective these factors may influence the composition of biological variables such as phytoplankton biomass, as well as the amount of nutrients within the waterbody. Observations in Fangar Bay, a small, shallow, stratified and micro-tidal bay in the Ebro Delta (NW Mediterranean Sea), have shown that during wind episodes the biological variables undergo sudden variations in terms of concentration and distribution within the bay. The Regional Ocean Model System (ROMS) coupled with a nitrogen-based nutrient, phytoplankton, zooplankton, and detritus (NPZD) model has been applied to understand this spatio-temporal variability of phytoplankton biomass in Fangar Bay. Idealised simulations prove that during weak wind events (< 6 m·s−1), the stratification is maintained and therefore there is not dynamic connection between surface and bottom layers, penalizing phytoplankton growth in the whole water column. Conversely, during intense wind events (> 10 m·s−1) water column mixing occurs, homogenising the concentration of nutrients throughout the column, and increasing phytoplankton biomass in the bottom layers. In addition, shifts in the wind direction generate different phytoplankton biomass distributions within the bay, in accordance with the dispersion of freshwater plumes from existing irrigation canals. Thus, the numerical results prove the influence of the freshwater plume evolution on the phytoplankton biomass distribution, which is consistent with remote sensing observations. The complexity of the wind-driven circulation due to the bathymetric characteristics and the modulation of the stratification implies that the phytoplankton biomass differs depending on the prevailing wind direction, leading to sharp Chl a gradients and complex patterns.

Sea-levels will rise, even with stringent climate change mitigation. Mitigation will slow the rate of rise. There is limited knowledge on how the costs of coastal protection vary with alternative global warming levels of 1.5°C to 4.0°C. Analysing six sea-level rise scenarios (0.74m to 1.09m, 50th percentile) across these warming levels, and five Shared Socioeconomic Pathways, this paper quantifies the economic costs of flooding and protection due to sea-level rise using the Dynamic Interactive Vulnerability Assessment (DIVA) modelling framework. Results are presented for World Bank income groups and five selected countries from the present to 2100. Annual sea flood damage costs without additional adaptation are more influenced by socio-economic development than sea-level rise, indicating there are opportunities to control risk with development choices. In contrast, annual sea dike investment costs are more dependent on the magnitude of sea-level rise. In terms of total costs with adaptation, upper middle, low middle and low income groups are projected to have higher relative costs as a proportion of GDP compared with high income groups. If low income countries protected now, flood costs could be reduced after 2050 and beyond. However, without further adaptation, their coasts will experience growing risks and costs leaving them increasingly reliant on emergency response measures. adaptation. Without mitigation or adaptation, greater inequalities in damage costs between income groups could result. At country level, annual sea flood damage costs without additional adaptation are projected to rapidly increase with approximately 0.2m of sea-level rise, leaving limited time to plan and adapt. SB, PG, KJ, RJ and RW were funded by the Department for Business, Energy and Industrial Strategy (BEIS) under contract UK SBS CR18083. ASA, SB, SJ, DL, RN, RT and AV were funded by the European Union’s Seventh Programme for Research, Technological Development and Demonstration under grant agreement No. 603396 (RISES-AM project).

Recent advances in numerical modeling, satellite data, and coastal processes, together with the rapid evolution of CMEMS products and the increasing pressures on coastal zones, suggest the timeliness of extending such products toward the coast. The CEASELESS EU H2020 project combines Sentinel and in-situ data with high-resolution models to predict coastal hydrodynamics at a variety of scales, according to stakeholder requirements. These predictions explicitly introduce land discharges into coastal oceanography, addressing local conditioning, assimilation memory and anisotropic error metrics taking into account the limited size of coastal domains. This article presents and discusses the advances achieved by CEASELESS in exploring the performance of coastal models, considering model resolution and domain scales, and assessing error generation and propagation. The project has also evaluated how underlying model uncertainties can be treated to comply with stakeholder requirements for a variety of applications, from storm-induced risks to aquaculture, from renewable energy to water quality. This has led to the refinement of a set of demonstrative applications, supported by a software environment able to provide met-ocean data on demand. The article ends with some remarks on the scientific, technical and application limits for CMEMS-based coastal products and how these products may be used to drive the extension of CMEMS toward the coast, promoting a wider uptake of CMEMS-based predictions. The work of UPC team included in this paper has been funded by the Ecosistema-BC Spanish Research Project (CTM2017-84275-R/MICINN-AEI-FEDER,UE) of the 2017 RETOS State Research Program.

Operational morphodynamic modelling is becoming an attractive tool for managers to forecast and reduce coastal risks. The development of highly sophisticated numerical models during the last decades has underpinned the simulation of beach morphological evolution due to wave impacts. However, there are still some fundamental aspects, such as the bathymetric uncertainty, that needs to be regularly updated in the modelling chain to avoid a worthless forecast. It is also very well known that the surf zone is the most highly dynamic area although the bathymetry changes between certain limits. In this work, we explore the influence of bathymetric changes in morphodynamic forecasts. XBEACH is used to model the morphological response of a dissipative urban low-lying sandy coastal stretch (Barcelona, Spain) for different forecasted storms to determine the uncertainty bands of predicted coastal erosion and flooding. We consider as benchmarks the results of XBEACH simulations fed with the bathymetric information taken from existing nautical charts. An analysis of the possible beach states of the studied area following the Wright and Short (1984) is later performed to determine a range of topo-bathymetric configurations that will be used to run the model again. These new simulations are used to determine the uncertainty of the erosion and flooding results. The energy content of the storm in terms of intensity and duration uncertainty is also considered in the analysis. The proposed ensemble approach will serve to determine the likelihood of the modelling forecast outputs. Such statistical characterization is aligned with ensemble forecasting in meteo-oceanographic fields and will provide robust information for coastal decision making, for instance when considering proactive rapid deployment measures against a forecasted storm.

Estuaries and coastal bays are areas of large spatial-temporal variability in physical and biological variables due to environmental factors such as local wind, light availability, freshwater inputs or tides. The physical characteristics of an estuary affect its hydrodynamics. These in turn modify the behaviour of biological variables such as the concentration of chlorophyll a (Chl a). In a small-scale, micro tidal bay such as the Fangar Bay (Ebro Delta), hydrodynamics is influenced above all by local winds, as well as by fresh water contributions. The results of two field campaigns and Sentinel-2 images show how the concentration of Chl a is affected by strong wind episodes typical of this area (NW-E winds). With these episodes of strong wind (> 10 m-s-1) mixing occurs in the water column causing an increase in the concentration of Chl a. On the other hand, with sea breezes (< 6 m-s-1) the water column is stratified causing a decrease in the Chl a concentration. However, the spatial-temporal variability of Chl a in small-scale estuaries and coastal bays is quite complex due to the many factors involved and deserves more intensive field campaigns and additional numerical modelling efforts.

The ocean is an essential part of the planet that plays a crucial role in the global life system and provides vital resources for humanity. Coastal areas are the most affected by direct pressure from human activity, and their management is very complex due to the multiple interconnected processes that occur there. To conserve and protect our coastal areas, we must observe and understand how they interact. Despite its paramount importance to society, there are fundamental gaps in coastal observing and modelling. Therefore, current forecasting systems limit our capacity to manage this narrow border between land and sea sustainably. Improved numerical models and sustained observations of our ocean are needed to make informed decisions and ensure that human-coastal interaction is sustainable and safe.EuroSea initiative is an innovation action of the European Union entitled "Improvement and integration of the European oceans Observation and prediction systems for the sustainable use of the oceans'. EuroSea brings together the leading European players in the ocean observation and forecasting with users of oceanographic products and services and provides high-resolution coastal operational prediction systems in domains such as ports, beaches and nearby coastal waters.In the EuroSea project framework, we present a 3D hydrodynamic tool to improve Barcelona's beaches' inner dynamics solution. We use the Coupled Ocean-Atmosphere - Wave - Sediment Transport (COAWST) Modeling System that utilizes the Model Coupling Toolkit to exchange prognostic variables between the ocean model ROMS, wave model SWAN, and the Community Sediment Transport Modeling System (CSTMS) sediment routines. As part of the system, the wave and ocean models run with nested, refined, spatial grids to provide increased resolution, scaling down to resolve nearshore wave-driven flows, all within selected regions of a larger, coarser-scale coastal modelling system.Bathymetry was built using a combination of bathymetric data from EMODnet (European Marine Observation and Data Network), and specific high-resolution sources provided by local authorities. Copernicus products have driven these high-resolution simulations.Results have been validated with field campaigns data, displaying preliminary agreements between model outputs and in-situ observations. The model provides results that will be used to study interactions between sea-level hazards, economic activity, and risk. These results will develop new forecast capabilities, such as erosion and flooding, rip currents, floating debris and flushing times.Finally, we look ahead to the future of the operational prediction systems as useful tools to make informed decisions, minimize risks and improve environmental management.

This article investigates water circulation in small-scale (~10 km2), shallow (less than 4 m) and micro-tidal estuaries. The research characterizes the hydrodynamic wind response in these domains using field data from Fangar Bay (Ebro Delta) jointly with three-dimensional numerical experiments in an idealized domain. During calm periods, field data in Fangar Bay show complex water circulation in the inner part of the estuary owing to its shallow depths and positive estuarine circulation in the mouth. Numerical experiments are conducted to investigate wind-induced water circulation due to laterally varying bathymetry. For intense up-bay wind conditions (wind intensities greater than 9 m&middot, s&minus, 1), an axially symmetric transverse structure occurs with outflow in the central channel axis and inflow in the lateral shallow areas. These numerical results explain the water circulation observed in Fangar Bay during strong wind episodes, highlighting the role of the bathymetry in a small-scale environment. During these episodes, the water column tends to homogenize rapidly in Fangar Bay, breaking the stratification and disrupting estuarine circulation, consistent with other observations in similar domains.

Accurate suspended sediment concentration measurements are key to understand and quantify the sediment transport patterns in the surf and swash zones. One of the most widely used instruments to collect suspended sediment concentrations is the Optical Backscatter Sensor (OBS). However, the OBS is known to give erroneous readings when deployed in bubbly environments like the surf zone. The present study aims to quantify the influence of an aerated wave breaking environment on the OBS sediment concentration measurements. Experiments are performed in a large wave flume, which ensures full air entrapment under plunging breaking waves, and avoids scale effects that could affect the volume of entrapped air, the air bubble penetration depth and the residence time of air bubbles in the post-breaking turbulent eddies. OBS measurements are obtained at 66 locations along a fixed bed profile for 14 regular breaking wave conditions. In the absence of suspended sediment particles, OBS voltage measurements are used as a proxy for air bubble content. The presented OBS results show peaks up to 1.49 V (31% of the OBS measurement range, corresponding to 16 g/l for sediment with d50 = 0.25 mm) produced by air bubbles in the most energetic tested wave breaking conditions, while the maximum time-averaged value obtained is 0.48 V (10% of the OBS measurement range, corresponding to 5 g/l). The results highlight the importance of considering the presence of air bubbles where OBS are deployed to measure suspended sediment concentrations. A good correlation is found between the breaker depth index and the air bubble distribution and two predictive formulas are derived to forecast the area of air bubble influence in the surf zone. We offer our gratitude to the CIEM staff, especially to Joaquim Sospedra for his endurance and leadership. The work described in this paper was supported by the European Community’s Horizon 2020 Programme by means of the Hydralab+ Project (contract number 654110). This paper contributes to the Hydralab+ legacy together with a set of coordinated papers in other journals. Finally we acknowledge the economical funding and support received by the Secretaria d´Universitats i Recerca del Dpt. d´Economia i Coneixement de la Generalitat de Catalunya (Ref. 2017SGR00773).

Working in the coastal marine environment is highly challenging, among other reasons, due to the variety of extreme, seasonal, short and long-term environmental conditions that affect the coastline, beaches, infrastructures and port operations. The maritime climate directly affects the construction and maintenance of port infrastructures, the access of ships to ports, the safety of cargo handling operations, emergency response or the environmental management of effects of port operations. Currently, the ability to predict the sea state from a few hours to days has reached levels of precision and reliability unbelievable a few years ago. And all this, in combination with numerical measurements and predictions, has enabled significant advances in knowledge about meteorological and oceanographic conditions, making possible the development of forecasting systems to provide real, accurate and safe support in decision making in ports.SAMOA initiative (System of Meteorological and Oceanographic Support for Port Authorities), developed by Spanish Port System (Puertos del Estado), in cooperation with Spanish Port Authorities, provides high-resolution coastal operational prediction systems in domains such as harbours and nearby coastal waters.We present a high-resolution coastal operational prediction system which simulates the hydrodynamic in the Spanish Mediterranean Ports from April to September 2019. Bathymetry was built using a combination of bathymetric data from GEBCO (General Bathymetric Chart of the Oceans), and specific local high-resolution sources provided by port authorities. Daily updated hourly winds and heat and water fluxes from the Spanish Meteorological Agency forecast services were used as a surface forcing. The Regional Ocean Modelling System, ROMS, was used to investigate the hydrodynamics.Three-day forecast of three-dimensional currents and other oceanographic variables, such as temperature, salinity, and sea level, were produced. These results were compared with field campaigns data, displaying agreements between model outputs and in-situ observations. Finally, a look ahead to the future of the operational prediction systems is provided as a useful tool to make informed decisions around port safety and efficiency.We would like to acknowledge financial support from ECOSISTEMA-BC Project (CTM2017-84275-R), funded by the Spanish State Research Agency.

The sustainable management of coastal areas with limited natural resources and subject to high anthropogenic pressures, based on complete forecast and analysis systems, is one of the main concerns of coastal authorities. Paradoxically, current oceanographic operational predictions are often insufficient to provide a good description of these regions due to low resolution/accuracy, the omission of relevant land-sea interactions, and the inadequate inclusion in the models of physical processes specific to the coastal fringe.The CURAE project bridges this gap between the regional scales and the local coastal needs by establishing a 2-way connection between the existing CMEMS products and an innovative coastal information system (required by coastal water managers and littoral users alike) that considers hydro-morphodynamic interactions in an operational manner. The paper will present a new set of robust downscaling and coupling tools that have been developed to enhance the coastal dimension of present CMEMS products. The main advances refer to coastal processes not commonly incorporated in oceanographic predictions and that interact with the shelf sea, including the continental discharge in terms of water, sediment and nutrient fluxes.The project is focused on two hydrodynamically contrasting sites with different uses (aquaculture and dredging) that demonstrate the added value and potential of CMEMS for coastal applications. The first case is the semi-enclosed microtidal Fangar Bay in the Ebro Delta (Spanish Mediterranean), in which bivalve farming coexists with tourism and nutrient- and sediment-laden freshwater discharges from rice fields in a hydrodynamically weak environment interacting with active domain geometries. The second study case is the macrotidal Wadden Sea/German Bight estuaries area, with concentrated plus distributed land discharge and significant dredging activities required for port operations. To ensure that the tools and conclusions derived from the project are as generic as possible, different numerical approaches (structured vs. unstructured grids) have been applied at each site and will be compared and discussed in the paper. The obtained results illustrate the benefits of quantitative forecasts for the healthy functioning of coastal systems, while proving the potential of CMEMS for supporting sustainable interventions in the coastal zone. The obtained advances are encouraging from scientific and application standpoints and underpin the need for a high-resolution coastal extension of CMEMS.

In this work, the effects of storm representation on damage measurements of a breakwater are studied in a small-scale physical wave flume. In particular, a two-layer breakwater with cubic armor units randomly placed is considered. A storm recorded in the Mediterranean Sea is the basis to analyze the armor layer damage. Storm sea states are represented in the laboratory using four different methodologies: i) Real storm methodology (RSM, used here as benchmark test) ii) Classical methodology (CM) iii) Equivalent Magnitude Storm with a triangular shape (EMSI) and iv) Equivalent Magnitude Storm with a trapezoidal shape (EMSA). For the four methodologies, the experiments are repeated five times. Considering laboratory occupation times, results suggest that a minimum of five repetitions of CM should be performed to obtain an average damage value that can represent the average damage given by RSM. Although this recommendation is linked to the tested conditions, it provides useful information to set-up experiments dealing with similar breakwater and wave conditions.

SAMOA (Sistema de Apoyo Meteorológico y Oceanográfico de la Autoridad Portuaria) is the latest initiative of Puertos del Estado, the Spanish Public State Port Agency, to enhance the delivery of user-customised operational met-ocean information to aid Spanish Port Authorities making harbour safety, environmental management and operational decisions. This initiative provides high-resolution coastal operational prediction systems in domains such as harbours and nearby coastal waters. Forecast systems implemented are fully operational from January 2017 for nine Spanish ports in the Mediterranean, the Iberian Atlantic and the Canary Islands. This paper provides an end-to-end description of these SAMOA systems that are based on high-resolution ROMS model applications. The SAMOA systems are CMEMS downstream services, being the coastal models nested into the regional IBI forecast solution. At the surface, SAMOA systems use as forcing daily updated hourly winds and heat and water fluxes from the Spanish Meteorological Agency forecast services. Highlights from the scientific pre-operational model evaluation phase and the multi-parametric validation are shown, illustrating agreements between SAMOA products and in-situ and remoted sensed observations. To this aim, skill metrics (such as bias, errors, Taylor diagrams and correlations) are presented. Finally, a look ahead to future SAMOA developments and operational innovations is provided.

Storm surges are one of the main drivers for extreme flooding at the coastal areas. Such events can be characterized with the maximum level in an extreme storm surge event (surge peak), as well as the duration of the event. Surge projections come from a barotropic model for the 1950&ndash, 2100 period, under a severe climate change scenario (RCP 8.5) at the northeastern Spanish coast. The relationship of extreme storm surges to three large-scale climate patterns was assessed: North Atlantic Oscillation (NAO), East Atlantic Pattern (EAWR), and Scandinavian Pattern (SC). The statistical model was built using two different strategies. In Strategy #1, the joint probability density was characterized by a moving-average series of stationary Archimedean copula, whereas in Strategy #2, the joint probability density was characterized by a non-stationary probit copula. The parameters of the marginal distribution and the copula were defined with generalized additive models. The analysis showed that the mean values of surge peak and event duration were constant and were independent of the proposed climate patterns. However, the values of NAO and SC influenced the threshold and the storminess of extreme events. According to Strategy #1, the variance of the surge peak and event duration increased with a fast shift of negative SC and a positive NAO, respectively. Alternatively, Strategy #2 showed that the variance of the surge peak increased with a positive EAWR. Both strategies coincided in that the joint dependence of the maximum surge level and the duration of extreme surges ranged from low to medium degree. Its mean value was stationary, and its variability was linked to the geographical location. Finally, Strategy #2 helped determine that this dependence increased with negative NAO.

F.-Pedrera Balsells, M.; Mestres, M.; Fernandez, M.; Cerralbo, P.; Espino, M.; Grifoll, M., and Sanchez-Arcilla, A., 2020. Assessing nature based solutions for managing coastal bays. In: Malvarez, G. and Navas, F. (eds.), Global Coastal Issues of 2020. Journal of Coastal Research, Special Issue No. 95, pp. 1083–1087. Coconut Creek (Florida), ISSN 0749-0208.This work investigates the hydrodynamic response of two small and shallow bays located in the Ebro Delta, in order to solve the problems affecting mussel farms, such as the high temperatures reached in the summer period (>28 °C), causing the death of these bivalves, and the limited water renewal that causes anoxia within the bay. Nature Based Solutions are described focusing on two aspects: one, modifying the flow of these drainage channels, increasing the arrival of freshwater to the bays; and two, opening a gap in the sand bars so that there is a flow of sea water in and out through the innermost zone, which is where both bays have greater problems of water renewal. The impact of those solutions simulated with the Regional Oceans Modeling System (ROMS), consist of a set of nested domains that use CMEMS-IBI data for the initial and open boundary conditions (coarser domain). To validate the numerical model, data from in situ campaigns have been used for one full year (2014) for Alfacs Bay, and for the summer period (July-August 2017) for Fangar Bay. In addition, the Sea Surface Temperature (SST) is also studied as an indicator to reduce the mortality problems of mussels, but the results obtained do not reduce this variable. What the results do show is a decrease in residence time in both bays for both experiments, with the increase in flow being more viable than the increase in sand bar breakage.

This is an Accepted Manuscript of an article published by Taylor & Francis Group in Journal of Hydraulic Research on 2018, available online at: http://www.tandfonline.com/10.1080/00221686.2017.1315748 Typical morphodynamic laboratory tests have been carried out at small scales and without sufficient coverage or resolution. These limitations, applying particularly to accretive tests, have obstructed reliable observations and restricted modelling capabilities. Here we present experiments with erosive/accretive waves acting on a large scale flume bed profile. The paper reports a set of high-quality hydro-morphodynamic data. The analysis is focused on net transport rates and how these patterns change between different accretive conditions. The measured velocity and acceleration skewness are presented and discussed, linking the net transport over the bar to the measured hydrodynamics and sediment concentrations. The resulting profile behaviour is discussed as a function of hydro-morphodynamic settings to facilitate comparisons with other datasets.