A Mediterranean coastal database for assessing the impacts of sea-level rise and associated hazards

We have developed a new coastal database for the Mediterranean basin that is intended for coastal impact and adaptation assessment to sea-level rise and associated hazards on a regional scale. The data structure of the database relies on a linear representation of the coast with associated spatial assessment units. Using information on coastal morphology, human settlements and administrative boundaries, we have divided the Mediterranean coast into 13 900 coastal assessment units. To these units we have spatially attributed 160 parameters on the characteristics of the natural and socio-economic subsystems, such as extreme sea levels, vertical land movement and number of people exposed to sea-level rise and extreme sea levels. The database contains information on current conditions and on plausible future changes that are essential drivers for future impacts, such as sea-level rise rates and socio-economic development. Besides its intended use in risk and impact assessment, we anticipate that the Mediterranean Coastal Database (MCD) constitutes a useful source of information for a wide range of coastal applications.Peer ReviewedPostprint (published version

Sensitivity of storm-induced hazards in a highly curvilinear coastline to changing storm directions: the Tordera delta case (NW Mediterranean)

Extreme coastal storms, especially when incident in areas with densely urbanized coastlines, are one of the most damaging forms of natural disasters. The main hazards originating from coastal storms are inundation and erosion, and their magnitude and extent needs to be accurately assessed for effective management of coastal risk. The use of state-of-art morphodynamic process-based models is becoming standard, with most being applied to straight coastlines with gentle slopes. In this study, the XBeach model is used to assess the coastal response of a curvilinear sensitive deltaic coast with coarse sediment and steep slopes (intermediate-reflective conditions). The tested hypothesis is that changes in wave direction may cause large variations in the magnitude of storm-induced hazards. The model is tested against field data available for the Sant Esteve Storm (December 2008), obtaining an overall BSS (Brier Skill Score) score on the emerged morphological response of 0.68. Later, the 2008 event is used as baseline scenario to create synthetic events covering the range from NE to S. The obtained results show that storm-induced hazards along a highly curvilinear coast are very sensitive to changes in wave direction. Therefore, even under climate scenarios of relatively steady storminess, a potential shift in wave direction may significantly change hazard conditions and thus, need to be accounted for in robust damage risk assessments.Peer ReviewedPostprint (published version

Morphological changes, beach inundation and overwash caused by an extreme storm on a low-lying embayed beach bounded by a dune system (NW Mediterranean)

The geomorphological evolution of a low-lying, micro-tidal sandy beach in the western Mediterranean, Pals beach, was characterized using airborne Light Detection and Ranging (LiDAR) data. Data were collected in prior to and six months after the impact of an extreme storm with a return period of approx. 50 years, with the aim of characterizing the beach's response to the storm. The use of repeated high-resolution topographic data to quantify beach geomorphic changes has allowed assessment of the accuracy of different proxies for estimating beach volume changes. Results revealed that changes in the shoreline position cannot accurately reproduce beach volume changes on low-lying beaches where overwash processes are significant. Observations also suggested that volume estimations from beach profiles do not accurately represent subaerial volume changes at large profile distances on beaches with significant alongshore geomorphological variability. Accordingly, the segmentation of the beach into regularly spaced bins is proposed to assess alongshore variations in the beach volume with the accuracy of the topographic data. The morphological evolution of Pals beach during the study period showed a net shoreline retreat (- 4 m) and a significant sediment gain on the subaerial beach (+ 7.5 m3/m). The net gain of sediment is mostly due to the impact of the extreme storm, driving significant overwash processes that transport sediment landwards, increasing volume on the backshore and dunes. The increase of volume on the foreshore and the presence of cuspate morphologies along the shoreline also evidence post-storm beach recovery. Observed morphological changes exhibit a high variability along the beach related to variations in beach morphology. Changes in the morphology and migration of megacusps result in a high variability in the shoreline position and foreshore volume changes. On the other hand, larger morphological changes on the backshore and larger inundation distances occur when the beach and the dunes are lower, favouring the dominance of overwash. The observed storm-induced morphological changes differ from predicted beach storm impacts because of spatial and temporal variations in the beach morphology, suggesting that detailed morphological parameters and indicators used for predicting beach vulnerability to storms should be regularly updated in order to represent the pre-storm beach conditions. Finally, observed morphological changes in Pals Bay evidenced a different behaviour between natural and urban areas, with better post-storm beach recovery on natural areas where the beach is not artificially narrowed.Peer ReviewedPostprint (author's final draft

Comparison of Coastal Vulnerability Index applications for Barcelona Province

The Coastal Vulnerability Index (CVI) is one of the simplest and commonly used methods to assess coastal vulnerability to sea-level rise (SLR) driven erosion and/or inundation. In this way, it is a common tool contributing to the decision-making process in long-term coastal planning and management. However, there is not a unique approach to be adopted, and existing ones can supply different information and, thus, promote different decisions. Within this context, the main goal of this paper is to compare and evaluate different methodologies to determine CVI, and to suggest the most appropriate approach that can be generically applied for coastal vulnerability assessment. For doing this, the approaches proposed by Gornitz (1991), Shaw et al. (1998), Thieler and Hammar-Klose (2000), and Lopez et al. (2016) are applied along the 160 km long the Barcelona coastline in the Spanish Mediterranean. Shaw et al.‘s (1998) method appears to be the more realistic approach to assess vulnerability of the Barcelona coast while the overall vulnerability level calculated by the equation proposed by Gornitz (1991) indicate a wide variability, from highly vulnerable to a very low level of vulnerability. This study shows that the ranking tables generated from site-specific databases may not be applicable elsewhere, and indicates that it might be prudent to develop site or region-specific ranking categories to compute the overall CVI in order to provide reliable inputs to local coastal zone management initiatives. Despite the potential bias in the categorization of the overall CVI classes and their expert opinion/judgment approval requirements, CVI tools help decision makers to take the necessary actions to increase the resilience of coastal zones to SLR.Peer ReviewedPostprint (published version

Management of estuarine beaches on the Amazon coast though the application of recreational carrying capacity indices

The purpose of this paper is to determine the Recreational Carrying Capacity of three estuarine beaches (Colares, Marudá and Murubira) on the Amazon coast of Brazil, based on the combined assessment of natural conditions and visitor facilities. In the final analysis, the carrying capacity of Colares beach was estimated to be 1089 visitors per day, and that of Murubira beach, 238 visitors per day. At Marudá beach, however, the inadequate quality of the water resulted in an RCC of zero, indicating that the beach should not be visited for recreational use. The results of this study may provide a valuable diagnostic tool for the development of future state and municipal coastal management programs. We believe that the procedures adopted in this study are applicable to other estuarine beaches on the Amazon coast, as well as in other estuarine beaches elsewhere with similar natural characteristics.Peer ReviewedPostprint (author's final draft

Impacts of sea-level rise-induced erosion on the Catalan coast

The final publication is available at Springer via http://dx.doi.org/10.1007/s10113-016-1052-xThe Catalan coast as most of the developed Mediterranean coastal zone is characterized by the coincidence of stresses and pressures on the natural system with a high exposure and low adaptive capacity. Due to this, climate change-induced effects will increase natural hazards and aggravate their associated impacts and, in consequence, it is necessary to assess their effects for proper long-term management. In this work, we assess the impact of sea-level rise (SLR)-induced shoreline retreat on the Catalan coast for three scenarios ranging from 0.53 to 1.75 m by the year 2100. Implications are analysed in terms of affectation of two main functions provided by beaches, i.e. recreation and protection. Obtained results show that CC will be a serious threat to analysed functions since the expected enhanced shoreline retreat will severely decrease the recreational carrying capacity and the capacity of protection in the near future under tested scenarios. The actual level of development along the coastal zone reduces the natural resilient capacity of beaches to SLR in such a way that the lack of accommodation space can be identified as a main factor for the estimated impacts.Peer ReviewedPostprint (author's final draft

The economic impact of sea level rise-induced decrease in the carrying capacity of Catalan beaches (NW Mediterranean, Spain)

Sea-level rise (SLR)-induced erosion will contribute significantly to the reduction of the surface of beaches worldwide. In the absence of adaptation measures, this implies a decrease in the recreational carrying capacity provided by beaches, which in turn could significantly affect the economies of the areas associated with the “sun-and-beach” tourism model. Here, we propose a methodology to assess the demand-side economic impact by applying an input/output analysis, assuming that the beach carrying capacity is linked to the potential tourism demand, and consequently, to tourism consumption and output. Moreover, to properly evaluate the spatial variations in the impact throughout the territory, the effects are downscaled to the county level using a set of location coefficients. The model is applied to Catalonia, one of the most visited coastal regions in the Mediterranean. Here tourism contributes approximately 11% of its gross domestic product (GDP) and most visitors are related to coastal tourism. Although SLR affects the entire region with relatively small spatial variations in the induced shoreline retreat, its impact on the beach carrying capacity per county and the number of potential users exhibits a large spatial variability. Considering the RCP8.5 scenario as a reference, Catalonia's key coastal tourism brands, Costa Brava and Costa Daurada, will be the most affected economically, with an expected GDP loss of approximately 2200 million € and 1820 million € (at 2019 values), respectively. Finally, these local estimations were used to identify where the greatest benefits/returns would be derived from implementing adaptation measures to the SLR. This analysis was done by normalising the GDP losses that could be avoided in each county, with the length of beaches needed to provide recreation services to sustain the tourism economy.This work was supported by the Spanish Ministry of Economy and Competitiveness (MINECO/AEI/FEDER, UE) in the framework of the M-CostAdapt project (CTM2017-83655-C2-1-R).Peer ReviewedPostprint (published version

The Tordera Delta, a hotspot to storm impacts in the coast northwards of Barcelona (NW Mediterranean)

The Catalan coast, as most of the developed Mediterranean coastal zone, can be characterized as a high-risk area to the impact of storms due to the large concentration of values together with the dominance of eroding shorelines. In consequence, any long-term coastal management scheme must include a risk analysis to permit decision makers to better allocate resources. This can be done in a nested approach in which hotspots are first identified along the coast at a regional scale and secondly, they are further analysed to produce dedicated risk reduction strategies. In this work, we apply the methodology developed within the RISC-KIT project for identifying and analysing coastal hotspots in the Catalan coast as a test for applying it to Mediterranean conditions. Obtained results show that this methodology is very efficient in identifying hotspots of storm-induced flooding and erosion at a regional scale. The adoption of the response approach resulted in the direct assessment of the hazards' probability distributions, which allowed for the selection of the severity of the hotspots to be identified. When a given coastal stretch behaves as a hotspot for both hazards, it is identified as a very highly-sensitive area to storm impacts. In the study area, the Tordera Delta possesses this condition of very high “hotspotness.” This has been demonstrated by the large and frequent damages suffered by the site during the past decades. The paper analyses different aspects related to the risk management of this area, including stakeholder actions.Peer ReviewedPostprint (published version

Un esquema metodológico para facilitar el uso de la gestión de riesgos en playas

En este trabajo se propone un esquema metodológico para introducir el anàlisis de riesgos en la gestión integral de playas. La gestión de playas se ha concentrado tradicionalmente en los usos recreativos de éstas sin tener en consideración sus processos geomorfológicos ni otros valores medioambientales, lo que da lugar a que muchas situaciones de riesgo queden excluidas de los processos directos de gestión. Para superar esta situación, se ha estudiado el desarrollo de un enfoque sistémico integrado que evalua al unísono las dimensiones sociales y las dimensiones ecológicas de eventos potenciales de riesgo. En una primera fase, el esquema propone la definición del perfil de riesgo de la playa, donde a partir de la construcción de relaciones causa-efecto se vinculan los posibles eventos de riesgo y se identifican los servicios del ecosistema-playa implicados. En una segunda fase se realiza la evaluación de riesgos, incluyendo su valorización y priorización. Esta herramienta debería servir de ayuda a los gestores para decidir dónde asignar recursos para hacer frente a los riesgos que afectan las diversas funcionalidades de las playas. Se presenta asimismo una validación de esta propuesta en la playa de S’Abanell (Blanes, Girona).Postprint (published version

Expectativas de los usuarios y necesidad de una gestión diferencial a lo largo de la Costa Brava: playas urbanas vs. playas naturales protegidas

Las playas son sistemas socioecológicos donde las dimensiones físicas, ecológicas, sociales y económicas interactúan, ofreciendo diversas funciones y servicios ecosistémicos que conducen a mejorar el bienestar humano. Si bien estos sistemas pueden brindar distintas funciones (por ejemplo protección, recreación, natural), tradicionalmente los gestores solo ha priorizado la recreación. Esto ha llevado a la homogeneización de las prácticas de gestión de playas, que en la actualidad están poco adaptadas a las distintas características de las playas y sus usuarios. Mientras la participación pública ha sido largamente recomendada, la toma de decisiones en gestión de playas suele involucrar solo un actor, siguiendo un estricto orden jerárquico. En dos playas «antagónicas» (natural protegida y urbana) se evaluaron y compararon las expectativas y percepciones de sus usuarios, que podrían sugerir la necesidad de una gestión diferencial. Detrás de una aparente homogeneidad, se detectaron diferencias significativas entre estas dos playas. Aunque ciertas preferencias «naturales» fueron comunes en ambas playas, los atributos naturales fueron la prioridad en el sistema natural protegido, así como los servicios lo fueron en el urbano. Sin embargo, es innegable la influencia del modelo turístico masivo tradicional sobre las expectativas de los usuarios. Es por ello necesaria la aplicación de modelos de gestión diferenciales en aquellas playas que posean características naturales singulares. Asimismo es necesario un esfuerzo en la educación e información de los usuarios, así como un compromiso real por parte de los gestores como piedra angular para el uso sostenible de estos sistemas socio-ecológicos.Postprint (published version