Wave extreme events can be understood as the combination of Storm-intensity, Directionality and Intra-time distribution. However, the dependence structure among these factors is still unclear. A methodology has been developed to model wave-storms whose components are linked together. The model is composed by three parts: an intensity module, a wave directionality module, and an intra-time distribution module. In the Storm-intensity sub-model, generalized Pareto distributions and hierarchical Archimedean copulas have been used to characterize the storm energy, unitary energy, peak wave-period and duration. In the Directionality and Intra-time sub-models, the wave direction (at the peak of the storm) and the storm growth–decay rates are linked to the variables from the intensity model, respectively. The model is applied to the Catalan coast (NW Mediterranean). The outcomes denote spatial patterns that coincide with the state of knowledge. The proposed methodology is able to provide boundary conditions for wave and near-shore studies, saving computational time and establishing the dependence of the proposed variables. Such synthetic storms reproduce the inter-variable co-dependence of the original data.
Las costas urbanas son el motor económico de muchas regiones al integrar las actividades relacionadas con la explotación portuaria y las derivadas del uso recreativo de las playas. El cambio climático modificará los equilibrios existentes obligando a una gestión del litoral distinta a la realizada hasta la fecha. El uso de medidas de mitigación más naturales como la plantación de praderas vegetadas o recuperación de frentes dunares puede constituir una opción plausible para mantener la resiliencia costera con unos costes económicos y
energéticos asequibles. En esta ponencia se analiza la eficacia de tales medidas desde el punto de vista de la protección costera y la explotación portuaria. Estas soluciones son evaluadas en distintos puntos de la costa Catalana mediante el uso de modelos numéricos y han sido desarrolladas en el marco del proyecto europeo RISES-AM.
És sobradament conegut que les prediccions d'onatge i vent a prop de la costa són menys precises en regions semi tancades que en mar obert. La costa Catalana és un clar exemple d'aquesta situació, amb un clima d'onatge controlat per fetch curts, batimetries complexes, camps de vent fortament variables tant en el temps com en l'espai, i combinacions de mar de fons i de vent que generen espectres bimodals. Aquestes característiques, típiques de dominis semi tancats, limiten la precisió de les prediccions d'onatge, obtenint errors de l'alçada d¿ona significant sobre el 10% i una clara subpredicció del període d'ona amb errors al voltant del 30%. La motivació d'aquesta treball és doncs millorar la capacitat de predicció d'onatge actual per la costa Catalana utilitzant el model d¿onatge SWAN v.4091. Per tal d'assolir aquest objectiu, es consideren tres línies de treball: (1) adaptar el model a les condicions de la costa Catalana, calibrant les corbes de creixement d'onatge per que reprodueixin millor la realitat, (2) examinar l'efecte de les corrents i el vent sobre l'onatge utilitzant sistemes acoplats i (3)considerar l'ús de malles no estructurades com a alternativa a sistemes aniuats tradicionals per tal d'obtenir prediccions d'onatge d'alta resolució en zones costeres reduint el temps de càlcul i evitant les condicions de contorn i els errors associats. Els resultats obtinguts concorden amb estudis previs en els quals la incapacitat dels models per reproduir correctament les corbes de creixement de l'onatge havia estat ja detectada. La proposta de modificació del terme de whitecapping presentada en aquest document ajuda a reduir la subpredicció del període d¿ona sense gairebé cap efecte en l'alçada d'ona. Aquesta correcció es aplicable a entorns similars. Tan mateix, la formulació proposada és només vàlida en els primers estats de generació d'onatge, i hauria de ser substituïda quan les ones adquireixen certa maduresa. Es consideren dues estratègies d'acoplament, un acoplament one-way en el que el camp de corrents s'introdueix directament en el mode d'onatge, i un acoplament two-way en el que models d'onatge, corrents i vent corrent paral·lelament. Els efectes de l'acoplament son avaluats durant períodes de calma i episodis més energètics. Els resultats obtinguts mostren que durant períodes de calma l'acoplament aporta ben poc, mentre que durant episodis energètics tals com intensificacions de corrents o vents canalitzats presenta més importància. Finalment cal tenir en compte que l'acoplament two-way presenta uns requeriments computacionals no sempre disponibles. En aquest sentit es proposa l¿ús de malles no estructurades com alternativa al mètode tradicional de malles aniuades. El principal avantatge de les malles no estructurades es que permeten treballar amb una única malla que té diferents resolucions segons el subdomini, millorant així la resolució en zones costeres. Un altre avantatge es la capacitat de reproduir millor la línia de costa o les zones al voltant de illes. Una de les parts més delicades de tot el procés consisteix en el disseny de les malles, on s¿ha de prestar especial atenció en els criteris considerats. La validació dels resultats, realitzada amb mesures de boies en zones costeres i dades de satèl·lit per mar obert, ens permeten afirmar que les malles no estructurades funcionen correctament a la zona d¿estudi. Finalment, es considera l¿adequació de les diferents propostes per a un sistema de predicció operacional. Queda demostrat que la modificació del terme de whitecapping millora decisivament la qualitat de les prediccions, mentre que l¿acoplament es recomana en funció de la capacitat de càlcul disponible. L¿ús de malles no estructurades per a tot el Mediterrani Occidental es considera com la primera opció, obtenint així onatge d¿alta resolució en zones costaneres reduint considerablement el temps de càlcul en comparació amb el sistema aniuat tradicional.
It is widely known that wind and wave predictions in the nearshore are less precise for semi enclosed domains than in the open ocean. The Catalan coast is a clear example of this situation, with a wave climate controlled by short fetches, complex bathymetry, high wind field variability in time and space, and sea and swell waves combined that generate bimodal spectra. These characteristics, typical for a semi-enclosed basin, limit the reliability of wave predictions in the area, with errors on the significant wave height around 10% and a clear under-prediction of the wave period with errors around 30%.
The motivation of this work is to improve the actual wave forecasting abilities for the Catalan Coast using the SWAN v.4091 wave model. In order to achieve this goal, three working lines are considered: (1)adapting the model to the Catalan coast conditions, tuning the wave growth rates included in the model to better reproduce the observed values, (2) evaluate the effect of the currents and wind into the wave field by using a coupled system and (3) consider the use of unstructured grids as an alternative to the traditionally nested systems in order to obtain high resolution wave forecasts in coastal areas reducing the computational time and avoiding the use of internal boundary conditions with their associated errors.
The results obtained support previous studies where the limited ability of the models to reproduce wave growth rates in young seas have been detected. The whitecapping term correction proposed in this document helps reducing under-prediction of the wave period observed with almost no effect on the significant wave height. This correction can be applied to similar environments. However, the proposed formulation is only suitable for the early stages of generation and should be discontinued after waves reach a certain maturity.
Two coupling strategies are considered, a one-way coupling where current fields are directly introduced into the wave model, and a two-way coupling where the waves, currents and winds models run in parallel. The effects of the coupling are evaluated during calm periods but also during energetic events. The results show that during calm conditions the coupling does hardly improve the results while during energetic events, such as superficial currents intensifications or wind jet events, the coupling has greater importance. However, the two-way coupling has extremely high computational requirements, not always available.
In this sense, the use of unstructured grids as an alternative to the traditional nested systems is presented. The main benefit of unstructured grids is that allows working with a single grid with different resolutions in each sub-domain, improving the resolution in coastal areas. Other advantage is the capacity to better reproduce the sharp coastline and the areas around the islands. The design of unstructured grids has been shown as one of the most delicate parts of this methodology, requiring special attention for the grid generation criteria. The validation of the results, performed with buoy measurements in the nearshore but also for the entire domain with altimetry measurements, allows stating that unstructured grids perform correctly in the study area.
Finally, the proposed work suitability for an operational forecasting system has been considered. The whitecapping term modification is proven to be decisive in the quality of the wave forecast, while the coupling is not always recommended depending on computational capabilities. The use of unstructured grids with a regional triangular mesh covering the entire Western Mediterranean sea is considered as the first option, providing accurate high resolution wave conditions near the coast with a clear reduction of the computational time in comparison with a traditional nested system.
És sobradament conegut que les prediccions d'onatge i vent a prop de la costa són menys precises en regions semi tancades que en mar obert. La costa Catalana és un clar exemple d'aquesta situació, amb un clima d'onatge controlat per fetch curts, batimetries complexes, camps de vent fortament variables tant en el temps com en l'espai, i combinacions de mar de fons i de vent que generen espectres bimodals. Aquestes característiques, típiques de dominis semi tancats, limiten la precisió de les prediccions d'onatge, obtenint errors de l'alçada d’ona significant sobre el 10% i una clara subpredicció del període d'ona amb errors al voltant del 30%. La motivació d'aquesta treball és doncs millorar la capacitat de predicció d'onatge actual per la costa Catalana utilitzant el model d’onatge SWAN v.4091. Per tal d'assolir aquest objectiu, es consideren tres línies de treball: (1) adaptar el model a les condicions de la costa Catalana, calibrant les corbes de creixement d'onatge per que reprodueixin millor la realitat, (2) examinar l'efecte de les corrents i el vent sobre l'onatge utilitzant sistemes acoplats i (3)considerar l'ús de malles no estructurades com a alternativa a sistemes aniuats tradicionals per tal d'obtenir prediccions d'onatge d'alta resolució en zones costeres reduint el temps de càlcul i evitant les condicions de contorn i els errors associats. Els resultats obtinguts concorden amb estudis previs en els quals la incapacitat dels models per reproduir correctament les corbes de creixement de l'onatge havia estat ja detectada. La proposta de modificació del terme de whitecapping presentada en aquest document ajuda a reduir la subpredicció del període d’ona sense gairebé cap efecte en l'alçada d'ona. Aquesta correcció es aplicable a entorns similars. Tan mateix, la formulació proposada és només vàlida en els primers estats de generació d'onatge, i hauria de ser substituïda quan les ones adquireixen certa maduresa. Es consideren dues estratègies d'acoplament, un acoplament one-way en el que el camp de corrents s'introdueix directament en el mode d'onatge, i un acoplament two-way en el que models d'onatge, corrents i vent corrent paral·lelament. Els efectes de l'acoplament son avaluats durant períodes de calma i episodis més energètics. Els resultats obtinguts mostren que durant períodes de calma l'acoplament aporta ben poc, mentre que durant episodis energètics tals com intensificacions de corrents o vents canalitzats presenta més importància. Finalment cal tenir en compte que l'acoplament two-way presenta uns requeriments computacionals no sempre disponibles. En aquest sentit es proposa l’ús de malles no estructurades com alternativa al mètode tradicional de malles aniuades. El principal avantatge de les malles no estructurades es que permeten treballar amb una única malla que té diferents resolucions segons el subdomini, millorant així la resolució en zones costeres. Un altre avantatge es la capacitat de reproduir millor la línia de costa o les zones al voltant de illes. Una de les parts més delicades de tot el procés consisteix en el disseny de les malles, on s’ha de prestar especial atenció en els criteris considerats. La validació dels resultats, realitzada amb mesures de boies en zones costeres i dades de satèl·lit per mar obert, ens permeten afirmar que les malles no estructurades funcionen correctament a la zona d’estudi. Finalment, es considera l’adequació de les diferents propostes per a un sistema de predicció operacional. Queda demostrat que la modificació del terme de whitecapping millora decisivament la qualitat de les prediccions, mentre que l’acoplament es recomana en funció de la capacitat de càlcul disponible. L’ús de malles no estructurades per a tot el Mediterrani Occidental es considera com la primera opció, obtenint així onatge d’alta resolució en zones costaneres reduint considerablement el temps de càlcul en comparació amb el sistema aniuat tradicional.
Mestres, M.; Sanchez-Arcilla, A.; González-Marco, D.; Espino, M.; Sierra, J.P.; Álvarez, E.; García Sotillo, M.; Capella, S.; Mora, J.; Llinás, O.; Cerralbo, P. MICRO International Conference p. 1-2 Data de presentació: 2016-06-26 Presentació treball a congrés
The fate and concentration of plastic pollutants in coastal seas depends on meteo-oceanographic factors and the multiple entry points in the domain. This will in turn control the implications for water quality, transmission of various biological diseases and the efficiency of recovery. In this paper we shall present a robust numerical model linked sequence that has been prepared jointly by Puertos del Estado and LIM-UPC. It is based on advanced, coupled meteo-oceanographic models that account for the main physical mechanisms responsible for circulation and dispersion. From here concentrations, times of renewal and trajectories can be derived with enough resolution so as to capture the important gradients in topography and bathymetry characteristic of coastal seas. The validation of these forecasts will require suitable data that address the various fields numerically predicted. This includes wind, atmospheric pressure, waves, currents and also the variations in mean water level. Such an observational effort needs also initial and boundary conditions that for dynamically narrow shelfs can shape the water, sediment and pollutant fluxes in the platform. In the paper we shall discuss the nested sequence that has been prepared and is now run pre-operationally for a set of Canary island harbours, where the Plocan data can provide valuable boundary information for model assessments. The simulated current dispersion patterns will be the basis to discuss impacts and recovery policy so as to maintain a water quality status in harbour areas and adjacent coastal tracts that comply with regulations and the requirements of coastal users.
Sanchez-Arcilla, A.; Losada, I.; Alvarez, A.; González-Marco, D.; Caceres, I.; Lara, J.L. International Conference on the Application of Physical Modelling to Port and Coastal Protection p. 1-9 Data de presentació: 2016-05-11 Presentació treball a congrés
This abstract provides an overview of the experimental work carried out at the MARHIS network formed by the Barcelona and the Santander research laboratories. The emphasis is on the role played by extremes as hydraulic drivers and also in terms of the observed responses. This has implications for the experimental generation equipment (waves, currents, wind) and for the observed responses (morphodynamic or structural). The paper discusses the joint capability of the two laboratories and the importance of reproducing and capturing those extremes for more efficient hydraulic tests.
Traditionally wave modelling has used a sequence of nested meshes to obtain high resolution wave fields near the coast. This supposes an uncertain error due to internal boundary conditions and physics at multiple scales. Both may distort the wave energy balance and for winds blowing from land there is the additional difficulty of wave trains travelling towards the offshore being hindered by the intermediate domain boundaries. Unstructured grids avoid multiple meshes and thus the problem of internal boundary conditions but may result in inconsistent fluxes of wave energy among cells, depending on mesh size and shape. This may distort the wave energy balance. Here we analyse high resolution wave simulations for a full meteorological year where high resolution meteorological models were available in a domain off the Catalan coast. This coastal case presents sharp gradients in bathymetry and orography and therefore correspondingly sharp variations in the wind and wave fields. We have carried out simulations with SWAN using a traditional nested sequence and a regional unstructured grid with varying resolution depending on a) distance to the coast line and b) gradients in bottom topography (as a proxy of associated gradients in wind and wave fields). Also a local unstructured grid covering the Catalan coast and nested to a regular system is included in the comparison. We are interpreting the results depending on the directional sector for the wind field since that determines fetch length, suitability of generation and dissipation terms in the wave model and compatibility with mesh size and shape. The obtained simulations are being compared to wave observations from buoys near the coast and remote sensing data all over the Western Mediterranean Sea. Additionally some test have been carried out in order to analyse the computational time required for each alternative, showing an important reduction when working with the regional unstructured grid.
Esta tesis se centra en el estudio de efectos de laboratorio que tienen lugar durante la medida de impactos violentos generados por olas rompientes sobre estructuras rígidas. Para su fin, se ha llevado a cabo una extensa campaña experimental en el canal de pequeña escala CIEMito del LIM-UPC BarcelonaTech y se ha realizado más de 4000 ensayos con oleajes regulares. Se ha analizado el efecto de la frecuencia de muestreo, la tipología del sistema de medida y el layout experimental en los resultados registrados. Tras confirmar experimentalmente el comportamiento prácticamente aleatorio del fenómeno y, para poder realizar comparativas estadísticamente validas, se ha realizado un alto número de repeticiones del mismo oleaje. Se ha analizado en particular los siguientes efectos: ¿Frecuencias de muestreo entre 50 y 19200 kHz¿Células de carga, sensores de presión y un innovador sistema táctil de medidas de presión¿Seis diferentes layouts experimentales. Los máximos resultados de fuerza y presión se han medido siempre a la máxima frecuencia de muestreo y se han obtenido diferencias del orden del 150% con los ensayos muestreados a 50 Hz.La resultante medida de la fuerza en todo el ancho del canal tiende a subestimar el valor de la fuerza cuando se compara con medidas en la porción central. Aunque en valor promedio los resultados son comparables, en el caso de los sensores de presión los resultados son más dispersos en comparación con los resultados de las células de carga. El sensor táctil de presión destaca por su elevada densidad espacial (196 sensores en un área de 49cm2) pero en su contra, requiere de una calibración dinámica y un set-up particular para su utilización en agua y para que los resultados sean comparables con los de los sistemas clásicos de medida. Para este trabajo se comparó una calibración con la caída de un martillo y con la caída de un volumen controlado de agua, siendo ésta última la seleccionada para estos ensayos. Entre los resultados obtenidos se destacaque a partir de una comparativa directa entre la integral de las presiones medidas del sensor táctil calibrado y la fuerza medida en la misma área por una célula de carga, se ha evidenciado errores del orden del ±20%. El sensor táctil tiende a subestimar las presiones de pico, aunque si se consideran los valores extremos medidos, los errores son del ±10%. Se ha evidenciado también un efecto de reducción del pico de presión cuando las medidas de presión están acopladas con medidas de células de carga. Aunque no hay una alternativa perfecta para esta tipología de medidas la combinación de los tres sensores parece la mejor solución posible. Las células de carga dan un resultado directo y muy fiable de la fuerza total, pero su instalación, sobretodo en ensayos de gran escala puede ser complicada. El sensor táctil tampoco se presenta como la alternativa absoluta a los sensores de presión y se aconseja un uso combinado para ensayos que requieran más altos niveles de precisión espacial que en magnitud. Una frecuencia de muestreo entorno a 4000 Hz en ensayos a pequeña escala presenta la justa combinación entre velocidad de muestreo y cantidad de datos registrados para detectar el fenómeno impulsivo generado por el impacto violento del oleaje en estructuras rígidas. Si se considera que se ha trabajado con una escala de trabajo alrededor entre 1/50 y 1/100, se propone una frecuencia de muestreo a escala prototipo entorno a 500 Hz. El seguimiento de estas recomendaciones metodológicas permite no sólo generar unas medidas más fiables sino también permitirá una mejor comprensión/evaluación de las posibles incertidumbres en fase de ensayo y análisis de datos. Una correcta medida del fenómeno impulsivo del impacto del oleaje en estructuras rígidas aporta más fiabilidad al proyecto de estructuras rompeolas.
Frau, L.; Marzeddu, A.; Dini, E.; Gracia, V.; Gironella, X.; Eriolo, A.; Zomparelli , A.; Sanchez-Arcilla, A. Journal of coastal research Vol. 75, num. Special issue 75, p. 851-855 DOI: 10.2112/SI75-171.1 Data de publicació: 2016-04 Article en revista
Present 3D printing technology allows the efficient design and construction of structures with complex shapes and high porosity satisfying biological and coastal protection demands. In this case, an array of ultra-porous tetrahedron shaped 3D printed artificial reef (UPTSAR) is proposed to be used as a submerged breakwater for both environmental enhancement and wave protection. The aim of this study is to analyse the wave-structure interaction effects and the resulting velocity and wave height fields. For this, two-dimensional small scale tests (1:15) using irregular waves were carried out in a wave flume facility at BarcelonaTech. The influence of wave steepness, relative freeboard, relative water depth and the porosity on wave Kinematics have been analysed. The paper will describe in detail the results obtained for the different tests. These results are used to evaluate the functionality of the UPTSAR as coastal protection structures.
This paper deals with the question of how to manage vulnerable coastal systems so as to make them sustainable under present and future climates. This is interpreted in terms of the coastal functionality, mainly natural services and support for socio-economic activities. From here we discuss how to adapt for long term trends and for short terms episodic events using the DPSIR framework.
The analysis is presented for coastal archetypes from Spain, Ireland and Romania, sweeping a range of meteo-oceanographic and socio-economic pressures, resulting in a wide range of fluxes among them those related to sediment. The analysis emphasizes the variables that provide a higher level of robustness. That means mean sea level for physical factors and population density for human factors. For each of the studied cases high and low sustainability practices, based on stakeholders preferences, are considered and discussed. This allows proposing alternatives and carrying out an integrated assessment in the last section of the paper. This assessment permits building a sequence of interventions called adaptation pathway that enhances the natural resilience of the studied coastal systems and therefore increases their sustainability under present and future conditions.
Flow intensification episodes lasting more than 12 h are observed occasionally at different locations along the Northwestern Mediterranean coast. In the last years, these pulses have hindered ship operations outside the Barcelona harbour, thus attracting the attention of the port authorities. In this paper, the strongest intensification events in the Barcelona coast area are quantified and characterized in order to identify the mechanisms which generate them. For this, current, sea level and meteorological measured and modelled data, at local and regional scale, are analysed. The results show that the flow accelerations are due to the combination of a narrow coastal shelf and the prevalence of a strong and sustained wind from the NE to SE. The synoptic atmospheric conditions that lead to this meteorological scenario are described. For one of the events, the presence and contribution to the current fluctuations of a coastal trapped wave, likely generated at the Eastern edge of the Gulf of Lions shelf, and other factors such as a freshwater discharge are also identified and discussed.
Ortego, M.I.; Egozcue, J. J.; Gomez, J.; Mösso, C.; Sanchez-Arcilla, A. International Conference on Advances in Extreme Value Analysis and Application to Natural Hazards p. 1 Data de presentació: 2015-09-17 Presentació treball a congrés
A statistical model of the future wave-extreme-climate under the RCP8.5 Climatic-Change scenario was required. Some variables of interest are energy, unitary energy, peak wave-period, duration, wave direction and growth-decay rates. Hierarchical Archimedean Copulae (HAC) and generalized Pareto distributions (GPD) have been used to model the first four variables, whereas the rest are characterized as individual variables. By examining the statistical model, the most relevant outcomes for future climate are less durable and energetic but more intense storms in the near and far future, an increase of wave peak-period in the far-future at the Roses bay, and a detachment of peak period from energy, unitary energy and duration in the far-future at the Ebre Delta.
Nephrops norvegicus es un importante recurso pesquero. La emergencia rítmica de la madriguera afecta las capturas. He estudiado dicho comportamiento en laboratorio investigando el efecto de ciclos lumínicos y de corrientes, demostrando que las mareas son un factor importante para gestionar el recurso. Mediante la técnica de secuenciación masiva y PCR en tiempo real sobre cDNA procedente del pedúnculo ocular, he elucidado el presunto mecanismo molecular que hay detrás de la regulación circadiana. Los resultados están de acuerdo con el conocimiento actual de los relojes biológicos en crustáceos, reforzando la idea que el proceso molecular de este grupo muestra algunas diferencias respecto el modelo consolidado de Drosophila melanogaster. Finalmente, he estudiado el comportamiento de emergencia en grupos de 4 cigalas organizadas en una jerarquía de dominancia, demostrando que los rangos más bajos son más vulnerables a la captura. Además he supuesto la existencia de mecanismos neuronales comunes entre comportamiento agonístico y non agonístico.
Nephrops norvegicus is an important fishery resource for Europe. Its rhythmic burrowing behavior is strictly related to catchability. Here I studied such behavior under laboratory conditions. I investigated the combined effect of light and current cycles demonstrating that tidal current is an important parameter to take in account in fishery management plan not only for Nephrops. Then I used a transcriptomics and RT-qPCR approach on cDNA extracted from the eyestalk to elucidate the putative molecular genetics mechanisms underlying circadian gene regulation. My data are in accordance with the current knowledge of the crustacean circadian clock, reinforcing the idea that the molecular clockwork of this group shows some differences with the established model in Drosophila melanogaster. Finally, I studied the burrow emergence behavior in group of 4 lobsters organized in dominance hierarchy demonstrating that lower ranks are more vulnerable to trawling. I hypothesized common neural mechanisms for agonistic and non-agonistic behaviors.
The reduction of greenhouse gas emissions and the resulting level of global warming remain uncertain. The thermal inertia of sea water commits us to a continued increase of mean sea level at decadal to centennial scales. The increase of human pressure and economic development in coastal zones will aggravate the problem. Conventional hard coastal defences are costly and increase the risk of catastrophic consequences in case of failure and may exacerbate the loss of territory (e.g. wetlands) through coastal squeeze. Adaptation needs to be a longterm process covering a wide range of management strategies.
To face this challenge, advanced scientific information on the processes and impacts will be a key element in order to develop robust adaptation pathways. Such pathways must take into account plausible high-end sea level rise scenarios and changes in storminess as well as quantitative impact projections. This information will allow an objective definition of tipping points for adaptation, the effect of feedbacks between the various components of the coastal system and the efficiency of novel coastal interventions. The adaptation pathways will allow defining a sequential set of interventions that facilitate the maintenance of coastal zones under all climate scenarios. The role of novel solutions promoting natural accretion mechanisms and using eco-morphodynamics to reduce coastal mobility needs to be explored as this has the potential to increase our chances to maintain healthy coastal systems under a variety of climates. From here we shall derive advance information on when, where and how to act, especially if change is at the high end, and this will facilitate the sustainability of these areas.
Within the EU research project RISES-AM- we are projecting impacts at global, regional and local scales. The global modelling is based on the DIVA code, addressing the flooding and erosion impacts worldwide. The regional modelling is based on a variety of hydro-morphodynamic models which reflect the site specific expertise and
available model calibration/validation. As illustration for the Mediterranean we are analysing the Catalan and Croatian coast, the former with a sequence of models specially adjusted for this coastal sector and the second one with a regional adaptation of DIVA. The level of resolution and processes at this regional scale is much higher than for the global analyses, including surges, wave action and long shore and cross shore sediment transport components together with the human pressures and infrastructures existing along the coast.
The local dimension can be illustrated by the Ebro Delta and other small-scale Mediterranean deltas where both
the vertical dynamics of the coastal plain and horizontal dynamics of the coastal fringe are being studied. For this
particular case the suitability of “green” interventions based on promoting natural accretion is also being
examined so as to assess its performance under present and future climate conditions. The resulting analysis will
allow identifying and partially quantifying adaptation tipping points that will be presented in the paper. This
will go associated to determining critical thresholds as a function of scale and related by way of illustration to
the availability of space or sediment. The combination of climatic pressures, coastal responses and the expected
socio economic evolution will be the building blocks for defining an adaptation pathway suited to the studied
coastal areas, illustrated in the paper by the three scales mentioned above.
Sanchez-Arcilla, A.; Sierra, J.P.; Gracia, V.; Garcia, M.; Jimenez, J.A.; Mösso, C.; Valdemoro, H. International Association for Hydraulic Research Congress p. 1-8 Data de presentació: 2015-07-01 Presentació treball a congrés
This document presents the impacts of future climatic conditions as a function of coastal typology. The impact assessment is carried out at decadal and storm scales showing how such a combination produces the worst levels of damage. From here the implications at a “predictive” scale up to 10 years and at a projective scale up to 10 decades is considered. The resulting impact consequences, normalized by their respective probability of occurrence allow calculating risk levels. For the more clear vulnerability hotspots the proposal in the paper is to use natural accretion mechanisms where the natural power of meteorological and oceanographic events can be put to use to contribute sedimentary inputs to a starving coastal zone. In the same manner the natural adaptive capacity of coastal systems could be enhanced if natural accommodation space is provided or considered for present and future planning. The paper ends with some conclusions on the development of a pathway for efficient responses to climatic change.
El Mapa para la Prevención de Riesgos Geológicos a escala 1:25.000 (MPRG25M) del Institut Cartogràfic i Geològic de Catalunya es un mapa multi-peligrosidad que incluye la representación de los fenómenos y indicios de actividad, así como las zonas susceptibles y la peligrosidad natural de los procesos generados por la geodinámica externa y interna. En el caso de los riesgos costeros una de las peligrosidades evaluadas es la inundación costera.
Tradicionalmente la inundación costera ha sido analizada a través del cálculo del remonte del oleaje mediante ecuaciones empíricas simples. El desarrollo de modelos numéricos permite abordar el problema desde una perspectiva más completa. El artículo muestra la metodología utilizada en el MPRG25M para determinar las zonas potenciales a la inundación a partir de la definición de una serie de escenarios extremos y la combinación de modelos numéricos hidrodinámicos y morfodinámicos en 2DH. Esta aproximación permite una gran resolución espacial y una reproducción del proceso más realista al considerar la playa como un elemento dinámico que interacciona con el oleaje incidente. A modo de ejemplo, la metodología utilizada se presenta para las playas del Golfo de Roses.
Coastal Zones: Solutions for the 21st Century bridges the gap between national and international efforts and the local needs for actions in communities where coastal zone challenges are faced daily. The solution-oriented approach covers issues of coastal zone management as well as responses to natural disasters. This work provides ideas on how to face the challenges, develop solutions, and localize management of common-pool resources. Coastal Zones targets academic stakeholders and coastal stakeholders who have local knowledge and experience but need a theoretical framework and a greater range of skills to make use of this experience.
Sanchez-Arcilla, A.; Gracia, V.; Garcia, M.; Jimenez, J.A.; Caceres, I.; Valdemoro, H. Coastal Sediments p. 1-14 DOI: 10.1142/9789814689977_0159 Data de presentació: 2015-05-13 Presentació treball a congrés
Although recent research has focused on erosive processes, natural accretion mechanisms have been known for many years, and they can provide an efficient solution to deal with sediment starved coasts. In this paper we shall review natural accretion mechanisms linked to sediment over-wash associated to wave storms in the Spanish Mediterranean. The analysis will encompass general marine flooding in a deltaic coastal fringe, for wide and narrow cross-shore profiles. The analyses will prove the natural capability of dynamic coasts to act in a resilient manner for cases of sediment starvation, such as it is the situation for many deltas and low-lying coasts in developed or developing countries.
Piero Lionello; Conte, D.; Scarascia, L.; Sanchez-Arcilla, A.; Sierra, J.P.; Mösso, C.; Hinkel, J. European Climate Change Adaptation Conference p. 224 Data de presentació: 2015-05-13 Presentació treball a congrés
With global emissions of greenhouse gases still increasing, it seems increasinly likely that global mean surface temperatures will exceed the international policy 'guardrail' of 2 degrees C relative to pre-industrial. The regional climate changes and biophysical impacts associated with this warming are highly uncertain, depending on the combination of forcings, and the timescale and spatial pattern of the response of the climate system. Further uncertainties in socioeconomic impacts arise from the unknown future trajectory of global population, economics and technology. Adaptation to future climate change requires scenarios which represent the 'uncertainty space' effectively, allowing decisions to be appropriately informed by a range of possible outcomes in a manageable way.
This presentation describes and explains scenarios for climate change above 2C, which explore the range of uncertainties at regional scales. This includes scenarios of a range of times of reaching specific warming levels of 2, 4 and 6C, arising from different emissions scenarios and different climate sensitivities, and scenarios of a range of regional climate states arising from different patterns of climate response. This focusses mainly on climate model projections from the 5th Coupled Model Intercomparison Project (CMIP5). It also includes scenarios of biophysical impacts from a number of different models in sectors such as agriculture and water resources amongst others, including projections from the Inter-Sectoral Impacts Model Intercomparison Project (ISI-MIP) amogst others, and scenarios of socioeconomic changes leading to different societal and economic impacts which may vary according to the extent and nature of adaptation. A key focus is on how the vast and complex uncertainty can be managed in such a way as to provide useful information for decision-makers.
Coastal zones are heavily populated and affected by human uses and infrastructures. Their natural resilience in the face of meteo-oceanographic pressures (mean sea level, waves, surges, etc.) has diminished even under recent climatic conditions. The expected adverse change to these climatic factors under future scenarios will aggravate the situation, requiring careful consideration of technical, economic and policy elements to design how coastal areas can be more effectively managed under varying climatic conditions. We expect that a diverse set of options will be appropriate depending on the natural and socio-economic settings.
In this paper, we shall discuss how the coastal zone concept has progressively broadened (e.g. recognized coastal fringe width) whereas adaptation to climate change requires a flexible approach to cope with changing conditions. The interpretation of this concept has been progressively fixed in a legal and administrative sense, through which it has also, in many cases, been spatially and jurisdictionally extended. And yet it is apparent that an important choice has to be made between shoreline position and beach width (for a given sediment volume) or between different adaptation strategies such as adapt/defend or retreat options (for a given set of coastal functions). This dilemma will be illustrated with several case studies (vulnerability hot spots) from the RISES-AM- project considering high end scenarios consistent with the IPCC AR5.
Traditionally data and analysis for erosive or Accretive wave conditions have been carried out at relatively small scales and without enough spatial coverage or resolution. This limits the in depth analysis and does not allow an undistorted (with respect to NATURE) and reliable analysis. In this paper we shall present a sample of 1 Erosive and 2 different Accretive wave sequences acting on a large scale beach profile experiment carried out at the CIEM wave flume in Barcelona. The experimental intervals are large enough to properly assess the impulsive response to large wave events and the underlying trends. We shall be looking at collocated hydro and morphodynamic time series with emphasis on the time scale of the drivers and responses. The subsequent analysis will deal with the different net transport rates between both Accretive conditions and within the different Accretion pattern of both tested conditions. We shall examine the velocity and acceleration skewness of the measured time series at two different points along the bar, while the net transport of the bar decrease with the adaptation of the profile to a more stable situation. The resulting beach behavior will be discussed as a function of the driving hydrodynamics and original beach settings.
Garcia, M.; Gracia, V.; Robichaux, L.; Kroger, A.; Gault, J.; Sanchez-Arcilla, A. Coastal Sediments p. 1-12 DOI: 10.1142/9789814689977_0166 Data de presentació: 2015-05-12 Presentació treball a congrés
Transient Defence Measures (TDM) are defined as actions that can be taken in advance in the coastal zone in order to reduce the impacts of an specific forecasted storm event. The design of such transient works requires detailed information of the hydrodynamic conditions of forecast events and an assessment of the effect on subsequent beach evolution. In this work, we present an analysis through numerical modelling of the efficiency of transitional dunes and temporary low-crested breakwaters considering the Mediterranean hydrodynamic conditions. The outcomes will serve to design a set of alternatives for mitigation of the coastal risks caused by extreme waves and high sea water levels in European coastal areas.
Operational oceanography predictions are now starting to include coupled wind, wave and current fields for open ocean and shelf domains. However the same product for coastal scales, including a) the non-linearity of coastal processes, b) the effect of continental rain driven discharge and c) the interaction with coastal structures are still in an early stage of development, both for the physical and numerical aspects.
In this paper we shall explore a coupled wind-wave-current model based on the COWAST system but including also the continental discharge and the effect of coastal structures, in particular shore parallel detached breakwaters. We shall apply such a pre-operational code to a test case near Barcelona, where the concept of transient coastal defences is being considered. The available in-situ and remote observations should also allow a robust calibration.
The operational oceanography simulations will be used to support the activation of these transient coastal defences and therefore illustrate the challenges required by coastal scales under rapid storm development such as is commonly found in the Western Mediterranean. The benefits of applying a robust and high resolution coupled hydro-dynamic system will become apparent from the stand point of transient coastal defence deployment and risk mitigation in heavily populated coastal areas.
This paper deals with the impact of future climates on coastal systems. It will focus on a number of vulnerability hot spots from the Spanish Mediterranean littoral, with a high degree of geo-diversity and a high pressure of use. The analysis will start from downscale scenarios from AR4 and AR5, using the mean sea level projections and wave storm features that correspond to a number of scenarios or families of scenarios. This will be followed by a critical analysis to determine the more damaging impacts of those future conditions, considering also local subsidence and the effect of vegetation since the resulting impact will be an integrated assessment of all these factors. The focus of the analysis will be on an urban beach from the Barcelona littoral and a natural beach from the Ebre Delta. This encompasses to extreme cases (for the Spanish Mediterranean scale) of no subsidence and large subsidence. The comparison will check the coastal behaviour under present and future conditions, to determine a sequence of impacts and actions that lead to the development of an adaptation pathway. With this the approach will follow in a natural manner the time evolution of climate projections where we shall reach an upper or high end limit of possible although unlikely conditions in the future (for instance for sea level rise we are considering a global average up to 2.0 m). The paper will end with a discussion and proposal for action based on the developed adaptation pathway and the downscale climatic projections for the Catalan coast and other coastal systems analysed in the RISES-AM- project.
Fernandez, D.; Mendes, R.; De Castro, M.; Dias, J.; Sanchez-Arcilla, A.; Gomez, M. Journal of marine systems Vol. 142, p. 40-46 DOI: 10.1016/j.jmarsys.2014.09.009 Data de publicació: 2015-02 Article en revista
The turbid plume formed at many river mouths influences the adjacent coastal area because it transports sediments, nutrients, and pollutants.; The effects of the main forcings affecting the Ebro turbid plume were analyzed using data obtained from the Moderate Resolution Imaging Spectroradiometer (MODIS) sensor onboard the Aqua and Terra satellites over the period 2003-2011. Composite images were obtained for days under certain river discharge conditions (different flow regimes) and different types of wind (alongshore and cross-shore winds) in order to obtain a representative plume pattern for each situation.; River discharge was the main driver of the Ebro River plume, followed by wind as the secondary force and regional oceanic circulation as the third one. Turbid plume extension increased monotonically with increased river discharge. Under high river discharge conditions (>355 m(3) s(-1)), wind distributed the plume in the dominant wind direction. Seaward winds (mistral) produced the largest extension of the plume (1893 km(2)), whereas southern alongshore winds produced the smallest one (1325 km(2)). Northern alongshore winds induced the highest mean turbid value of the plume, and southern alongshore winds induced the lowest one. Regardless of the wind condition, more than 70% of the plume extension was located south of the river mouth influenced by the regional oceanic circulation. (C) 2014 Elsevier B.V. All rights reserved.
The turbid plume formed at many river mouths influences the adjacent coastal area because it transports sediments, nutrients, and pollutants.; The effects of the main forcings affecting the Ebro turbid plume were analyzed using data obtained from the Moderate Resolution Imaging Spectroradiometer (MODIS) sensor onboard the Aqua and Terra satellites over the period 2003-2011. Composite images were obtained for days under certain river discharge conditions (different flow regimes) and different types of wind (alongshore and cross-shore winds) in order to obtain a representative plume pattern for each situation.; River discharge was the main driver of the Ebro River plume, followed by wind as the secondary force and regional oceanic circulation as the third one. Turbid plume extension increased monotonically with increased river discharge. Under high river discharge conditions (>355 m(3) s(-1)), wind distributed the plume in the dominant wind direction. Seaward winds (mistral) produced the largest extension of the plume (1893 km(2)), whereas southern alongshore winds produced the smallest one (1325 km(2)). Northern alongshore winds induced the highest mean turbid value of the plume, and southern alongshore winds induced the lowest one. Regardless of the wind condition, more than 70% of the plume extension was located south of the river mouth influenced by the regional oceanic circulation.
The major outcome of this document is a proposal for a new education program for the Danube- Black Sea (DBS) region. In principle the task focuses on different levels of education, namely (i) undergraduate students; (ii) postgraduate students (MSc, PhD); (iii) Postdoctoral fellows; and (iv) scientists. In addition, the requirements of technicians supporting all four groups are addressed within the framework of lifelong learning. Specialised training for professionals working in administrations (environment, navigation) is another goal of this agenda. The proposal for the education agenda is achieved through an analysis of the gaps and opportunities for an integrated approach towards a better alignment of international education and Human Resource development in the Danube Basin. Developments in the DBS include a number of initiatives and activities from before and after the 1990s (the fall of the Iron Curtain). In this context, the document reflects on the challenges including access to education programmes, new developments (including the credit transfer system) and the language requirements necessary for more substantial international cooperation. The document reflects on stakeholder opinions and provides a general discussion of the existing programs in the field of higher education and professional training(...).
The DANCERS project through a combination of stakeholder engagement, review of historical projects and programmes and state of the art science has built upon the EUSDR to develop a Strategic Research and Innovation Agenda (SRIA) to focus scientific effort across the entire Danube – Danube Delta – Black Sea (DBS) system. The added value of the implementation of this agenda will be a move towards sustainable
development resulting from scientifically grounded and informed decision-based – both integrated across disciplines and the full extent of the DBS system.
The development of the SRIA was achieved using a cross-disciplinary team of scientists who through a series of workshops worked directly with stakeholders from research and education, government and industry to identify their needs and the current opportunities. This was used to inform the scientific research direction to derive current state of the art and this knowledge in conjunction with a review of historical and current research projects and programmes was utilised to effectively shape the SRIA.
The document introduces the issues and challenges involved (Section 1), outlines the approaches used to develop the SRIA (Section 2) and the corresponding results (Section 3) were used to identify twenty one research topics. All of these correlated with at least two or more of the EUSDR Pillars (Connect the Region, Protecting the Environment, Building Prosperity, Strengthening the Region) and are detailed in Section 4.
Overall conclusions on the direction of Research and Innovation in the DBS System and the relevance and potential benefits of implementing research under one or all of the suggested SRIA research topics is included in the list on Section 5.
This book summarises the scientific case for the design and structure of a distributed research infrastructure on the Danube – Danube Delta – Black Sea macro system. Current gaps in our understanding of this environmental system are outlined, focussing particularly on the lack of cross-disciplinary research that spans the wide geographical extent of the Danube Basin and Black Sea and our failure, to-date, in synthesising environmental process dynamics at appropriate spatial and temporal scales.
The document details the technology and infrastructure required to meet these demands, focussing on two EU flagship projects: DANUBIUS-RI and DREAM. Together these initiatives have the potential to maximise opportunities for world leading environmental research in the Danube River Basin, the freshwater –marine transitional zone of the Danube Delta, and the Black Sea. This research will have wider impact outside the Danube region and will address current and emerging societal challenges. Moreover, by embracing new and emerging opportunities it will deliver a platform to enable cross-disciplinary research that integrates the environmental science and engineering disciplines with the social and economic sciences thereby advancing our ability to understand and manage dynamic environments such as the Danube – Danube Delta – and Black Sea.
Sierra, J.P.; Casas, M.; Moesso, C.; Virgili, M.; Sanchez-Arcilla, A. Natural hazards and earth system sciences Vol. 15, num. 8, p. 1695-1709 DOI: 10.5194/nhess-15-1695-2015 Data de publicació: 2015 Article en revista
The objective of the present work is to analyse how changes in wave patterns due to the effect of climate change can affect harbour agitation (oscillations within the port due to wind waves). The study focuses on 13 harbours located on the Catalan coast (NW Mediterranean) using a methodology with general applicability. To obtain the patterns of agitation, a Boussinesq-type model is used, which is forced at the boundaries by present/future offshore wave conditions extracted from recently developed high-resolution wave projections in the NW Mediterranean. These wave projections were obtained with the SWAN model forced by present/future surface wind fields projected, respectively, by five different combinations of global and regional circulation models (GCMs and RCMs) for the A1B scenario. The results show a general slight reduction in the annual average agitation for most of the ports, except for the northernmost and southernmost areas of the region, where a slight increase is obtained. A seasonal analysis reveals that the tendency to decrease is accentuated in winter. However, the inter-model variability is large for both the winter and the annual analysis. Conversely, a general increase with a larger agreement among models is found during summer, which is the period with greater activity in most of the studied ports (marinas). A qualitative assessment of the factors of variability seems to indicate that the choice of GCM tends to affect the spatial pattern, whereas the choice of RCM induces a more homogeneous bias over the regional domain.
Galea, A.; Grifoll, M.; Roman, F.; Mestres, M.; Armenio, V.; Sanchez-Arcilla, A.; Zammit, L. Environmental fluid mechanics Vol. 14, num. 6, p. 1405-1425 DOI: 10.1007/s10652-014-9351-6 Data de publicació: 2014-12 Article en revista
In the present paper, we use numerical simulation to investigate currents, mixing and water renewal in Barcelona harbour under typical conditions of wind forcing for the winter season. This site is of particular importance due to the interplay between touristic and commercial activities, requiring detailed and high-definition studies of water quality within the harbour. We use Large Eddy Simulation (LES) which directly resolves the anisotropic and energetic large scales of motion and parametrizes the small, dissipative, ones. Small-scale turbulence is modelled by the anisotropic Smagorinsky model (ASM) to be employed in presence of large cell anisotropy. The complexity of the harbour is modelled using a combination of curvilinear, structured, non-staggered grid and the immersed boundary method. Boundary conditions for wind and currents at the inlets of the port are obtained from in-situ measurements. Analysis of the numerical results is carried out based on both instantaneous and time-averaged velocity fields. First- and second-order statistics, such as turbulent kinetic energy and horizontal and vertical eddy viscosities, are calculated and their spatial distribution is discussed. The study shows the presence of intense current in the narrow and elongated part of the harbour together with sub-surface along-shore elongated rolling structures (with a time scale of a few hours), and they contribute to the vertical water mixing. Time-averaged velocity field reveals intense upwelling and downwelling zones along the walls of the harbour. The analysis of second-order statistics shows strong inhomogeneity of turbulent kinetic; [GRAPHICS]; .; energy and horizontal and vertical eddy viscosities in the horizontal plane, with larger values in the regions characterized by stronger currents. The water renewal within the port is quantified for particular sub-domain regions, showing that the complexity of the harbour is such that certain in-harbour basins have a water renewal of over five days, including the yacht marina area. The LES solution compares favourably with available current-meter data. The LES solution is also compared with a RANS solution obtained in literature for the same site under the same forcing conditions, the comparison demonstrating a large sensitivity of properties to model resolution and frictional parametrization.
Marzeddu, A.; Stagonas, D.; Gironella, X.; Sanchez-Arcilla, A. International Conference on the Application of Physical Modelling to Port and Coastal Protection p. 368-374 Data de presentació: 2014-09-30 Presentació treball a congrés
Deltaic systems illustrate the complexity of coasts subject to marine and fluvial factors, resulting in highly dynamic domains that are suffering a deficit in sediment supply (regulation of the catchment basin, impounded coastal transport...). For the Ebre Delta (Spanish Mediterranean coast) the sediment flux arriving to the delta has been reduced by more than 90%, resulting in a deltaic system that is eroding horizontally and subsiding vertically at rates that produce significant land loss and episodic flooding. The present situation will get aggravated at decadal time-scale due to the expected acceleration in sea level rise because of climatic change, with relative sea level rise rates (regional component plus subsidence) well above the values for other non-deltaic coasts and an impact likely enhanced by changes in storm patterns. The result would be further coastal re-shaping and, therefore, enhanced vulnerability and a growing deficit in system sustainability.
Our main research question is how to promote natural accretive processes that may compensate the above described deficits, so that the overall deltaic body becomes more resilient in the face of climatic change and increased development pressures.
Our research results will allow quantifying how marine/riverine flooding can contribute sediment volumes that may offset in part the deficit presented above. We shall analyse the efficiency of vertical accretion due to marine and riverine flooding and vegetation trapping. It will be done for a highly erosive transect located at the apex of the Ebre Delta, that will serve to present an actual illustration, based on measurements and some flux calculations, of how natural mechanisms can contribute to the sustainability of this type of deltaic systems. The paper will present the balance between short-term “inconveniences” (local flooding) and mid-term benefits (higher sedimentary volumes). These benefits will become more apparent at longer time scales and under future extreme climate scenarios, a clear message to stakeholders who look for reduced vulnerability at the short time scale and forget about the deficits at larger scales. In the conclusions we shall discuss the social and economic benefits of a naturally-based enhanced resilience.
The RISES-AM- project deals with the projections of impacts for vulnerable coastal systems under climatic variations. Starting from global scenarios we shall use regional projections for sea level rise, waves and storm surges together with some consistent socio-economic pathways. The project will employ an advanced set of models to assess impacts, focussing on flooding and erosion for the physical component and on coastal land uses and population migration for the socio-economic component. The development of such impacts in time will allow introducing conventional and novel coastal interventions for adaptation. The error bars in drivers and responses will introduce a significant uncertainty level that must be explicitly considered when developing an adaptive pathway, if it is to be seriously considered by the corresponding policy and decision makers.
Our main research question is whether the unavoidable limits in knowledge and accuracy may hinder decision making for vulnerable coastal zones that often require urgent choices even under present conditions.
Our research results will explore the feasibility of using a risk-based approach to assess coastal vulnerability and to compare the present adaptation deficit with that expected under future scenarios, particularly the high-end ones. The assessment will combine the long term (averaged) evolution with the occurrence of extreme (storm) events and their corresponding uncertainties, incorporating both of them into the analysis. The obtained adaptation pathways will address the effectiveness of novel (flexible) coastal engineering interventions, aiming to establish their performance under present and future conditions. This will be done for a number of case studies at local, regional and global scales and covering the defend/retreat/accommodate set of options so that the derived assessments contribute at various scales to climate change adaptation over time.
These results are considered to be relevant (societal implications) for the climate community, the coastal community and also for those involved in decisions related to the sustainability of the coast. This applies to present conditions (e.g. of coastal authorities deciding on coastal works) and to future conditions (land planning) and climate agreements.
With the release of the Intergovernmental Panel on Climate Change’s Fifth Assessment Report (IPCC AR5), climate change has again been identified as an important driver of change. Coasts are particularly vulnerable, directly affected by increasing sea levels and storminess, and other climate drivers, and accentuated by converging indirect landward and seaward influences. Adverse consequences include increased flooding, salinisation, erosion, and wetland and biodiversity loss. Several recent extreme meteorological events have caused catastrophic human and economic losses in coastal areas, including Cyclone Nargis (Myanmar, 2008), storm Xynthia (France, 2010), Hurricane Sandy (eastern United States, Canada and Caribbean, 2012) and Typhoon Haiyan (Philippines, 2013). Although coasts have always been hazardous places to live, global economic losses have significantly increased in recent decades. Climate change is exacerbating those risks. This article demonstrates how successive IPCC coastal chapters, have shifted from impacts to adaptation, assessing the relative role of climate change within a broader environmental framework, with increasing clarity and nuance, despite continuing uncertainties.
The high-resolution and coupled forecasting of wind, waves and currents, in restricted coastal domains, offer a number of important challenges; these limit the quality of predictions, in the present state-of-theart. This paper presents the main results obtained for such coastal domains, with reference to a variety of modelling suites and observing networks for: a) Liverpool Bay; b) German Bight; c) Gulf of Venice; and d) the Catalan coast. All of these areas are restricted domains, where boundary effects play a significant role in the resulting inner dynamics. This contribution addresses also the themes of the other papers in this Special Issue, ranging from observations to simulations. Emphasis is placed upon the physics controlling such restricted areas. The text deals also with the transfer to end-users and other interested parties, since the requirements on resolution, accuracy and robustness must be linked to their applications. Finally, some remarks are included on the way forward for coastal oceanography and the synergetic combination of in-situ and remote measurements, with high-resolution 3D simulations.
The accuracy of wave models in semi-enclosed-basins and orography-controlled wind conditions, especially during fetch-limited storm events, is known to be limited. Wind wave forecasting in the NW Mediterranean Sea is particularly demanding due to the characteristic sharp gradients of the wind and wave conditions. In this work we focus on the commonly observed underestimation of wave parameters even when the wind field is “correct” or overestimated. This is a small step to analyse such a discrepancy, where wind overestimation has been commonly used to get the “right” wave predictions for the “wrong” reason. Here we selected a suitable combination of nested meteorological and wave models to focus on the physics (in parameterized terms) of meso-scale wave generation in restricted domains. First, to better capture the typical sharp gradients in wind and wave fields under those conditions, the spatial resolution of the atmospheric model was progressively increased during a characteristic storm event from 18 km to 4 km; the corresponding frequency of the wind input was increased from 6 to 1 h. Second, the calculated rate of wave growth in the numerical model (i.e. the balance between the input term and the whitecapping dissipation) was analysed and tuned to match the observed local rate of wave growth. The rate of non-dimensional growth in the region of study, which was calculated using measurements along the fetch, turned out to be faster than simulated with the initial model settings and faster than reported in previous studies. Adjusting the wave growth rate in the model to the observations improved the estimated wave height by about 18% and the wave period by about 4%. Decreasing the grid size of the numerical models from 12 km to 4 km improved the timing of the wave peaks but not the maximum values of the storm. Increasing the frequency of the wind input (from 6 to 3 h) improved the estimation of the maximum wave height values (peaks) of the storm by about 13%. Summarizing, the results of this work showed that using high resolution and physically adjusted parameterizations in complex regions with strong wind and wave gradients such as the study area, it is possible to significantly reduce the under-estimation of wave parameters and to locally improve wave growth forecasting.
This study has been motivated by the limited accuracy of wave models under short-duration, fetch-limited conditions. This applies particularly to the wave period, in semi-enclosed domains with highly variable wind patterns as along the Catalan coast. The wave model SWAN version 40.91A is used here in three nested grids covering all the North-western Mediterranean Sea with a grid resolution from 9 to 1 km, forced with high resolution wind patterns from BSC (Barcelona Supercomputing Center) for two study periods, the winter 2010 and the spring 2011. The results are validated in eight locations with different types of instrumentations. In order to improve the results, a modification of the whitecapping term parameters is performed. Also the appropriate frequency integral range used to calculate the integral wave parameters is tested to be sure to compare the simulation results and the measurements for the same frequency interval. The results obtained show a clear improvement of the mean wave period and the peak period for the study area, decreasing considerably the negative bias observed previously, while almost no change is observed in wave height due to the proposed modifications. These results can be generalized to the Spanish Mediterranean coast and may be applicable to study areas with similar characteristics as the ones presented here: semi-enclosed domains with fetch-limited conditions and young sea waves.
Sanchez-Arcilla, A.; Gómez-Martínez, M.; Gracia, V.; Gironella, X.; Garcia, M. International Conference on Coastal Engineering p. 1-9 DOI: 10.9753/icce.v34.management.12 Data de presentació: 2014-06-17 Presentació treball a congrés
An analysis of the probability of failure of beaches along the Catalan coast (Northwestern Mediterranean) is presented. The failure condition is defined when waves are able to overtop the beach and reach the backshore. The analysis is performed by means of a verification equation where most of the related variables are assumed to be stochastic. The probability of failure of beaches is calculated by means of MonteCarlo simulations for present conditions and different climate change scenarios. At present 14% of the Catalan beaches fail the proposed protection function against storms. Under a high-end climate change projection (A1FI) 21% of beaches will fail.
Gracia, V.; Garcia, M.; Sanchez-Arcilla, A.; Gault, J.; Oller, P.; Fernández, J.; Sairouni, A.; Cristofori, E.; Toldrà, R. International Conference on Coastal Engineering p. 1-8 DOI: 10.9753/icce.v34.management.18 Data de presentació: 2014-06-17 Presentació treball a congrés
A new coastal early warning system CEWS called iCoast for the NW Mediterranean Sea is under development. It is composed of three numerical modules: meteorological, hydrodynamic and morphodynamic. The CEWS is designed for use on open sandy beaches, pocket beaches, secondary harbours as well as areas of coastal defences. A set of hotspots, prone to erosion or flooding, along the Catalan coast are being identified through a coastal hazard and risk mapping. Special attention is given to a set of intervention and emergency protocols based on the forecast outputs and the application of Quick Defence Measures (QDM) to diminish the risk. This paper presents the initial architecture and highlights the next step for QDM under the iCoast project.
Grifoll, M.; Gracia, V.; Guillén, J.; Espino, M.; Sanchez-Arcilla, A. International Conference on Coastal Engineering p. 1-5 DOI: 10.9753/icce.v34.sediment.51 Data de presentació: 2014-06-17 Presentació treball a congrés
River sediment dispersal on the near-shore of “flash-flood” rivers is investigated using a coupled wave-current-sediment transport model. Besòs and Llobregat rivers (short and mountainous rivers in NW Mediterranean Sea, near to Barcelona City) are used as examples to study the sediment transport under “flash-flood” regime. The modeling system COWAST which includes the coupling between the water circulation model ROMS and the wave model SWAN, is applied to assess the sediment dispersal mechanisms and deposition in the coastal area off the two river mouths. Preferential depositional areas such as mud-belts were identified from the simulations. The sediment dispersal pattern obtained by the model agrees with observational measurments. Complementary numerical simulations revealed sorting of sediment grain size in the cross-shelf direction.
The inner- and mid-shelf circulation response to strong cross-shelf winds is studied in Sant Jordi Bay (Catalan Sea) where those seaward winds are prevalent during fall and winter. Strong evidences of crossshelf circulation correlated with cross-shelf winds are obtained from a one-year current meter record at 43.5 m deep. During severe storms under unstratified conditions, the observations exhibit offshore flow in the entire water column resulting from a complex convergence in the along-shelf circulation. Under stratified conditions, the predominatly two-layer cross-shelf flow is intensified by cross-shelf winds. Along-shelf wind-driven circualtion in Sant Jordi Bay was week. From coupled atmosphere-wave-ocean numerical simulations (Warner et al., 2010), a complex flow is appreciated with the circulation pattern being a highly-dependent of the stratification conditions.