The coastal risk landscape application on the Catalan coast

Coastal zones concentrate an elevated number of values both natural and socio-economic, making them very vulnerable to the potential effects of natural hazards. Therefore, effective risk management requires a holistic analysis in which the multiple components that determine risk are taken into account. This has been addressed with use of The Coastal Risk Landscape concept, which can be defined as the integrated risk of coastal areas resulting from the action and interaction of natural and/or human induced hazards on existing values and assets. A methodology to assess coastal erosion and flood risk at a regional scale is presented using an integrated analysis of the main processes associated to forcings that induce erosion and flooding at different temporal scales (episodic, medium and long-term) as well as an analysis of the socio-economic consequences. This has been framed within the Source-Pathway-Receptor-Consequences (SPRC) model, in which the "pathway" has been adapted to represent each hazard by considering the different related processes acting at different timescales. To this end, each component (process) is first evaluated individually and classified into an intensity scale which allows an integration and comparison of their relative importance along the coast. An intensity scale associated with erosion components (episodic, medium and long-term) has been defined considering how the beach is affected, in terms of providing recreation and protection functions. Then, selected variables are used to assess the flooding components (flash floods, marine floods and inundation by sea level rise), related to the characteristics of their processes, and classified into an intensity scale.This permits an assessment of their individual contribution in order to analyse their relative contribution to the total risk. The consequences of erosion and flooding have been determined separately taking into account the most relevant impacts. In the case of erosion, socio-economic values of the two coastal functions analysed have been considered. Then, the erosion components are combined in a risk matrix, providing risk values for different coastal management targets (i.e. recreation and protection). In the case of flooding, the consequences are assessed by characterising the values at exposure based on an indicator that encompasses five categories (land use, population and social vulnerability, transport system, business settings and utilities). The total risk is expressed as the combination of the hazard and the exposure. All of this is integrated at a management scale, represented by the municipality. This methodology has been applied to 219 km of beaches along the Catalan coast (NE Spanish Mediterranean). Results obtained indicate that despite the generally good condition of the coast to provide recreation and protection functions at present, a future projection at 2035, which considers the medium and long-term erosion components (background erosion+ SLR-induced erosion), shows an increase in the risk to provide such functions. Thus, most of the municipalities with a tourism focus will be unable to support a recreational use, and the Maresme comarca will barely provide the required level of protection by 2035 year. Moreover, episodic flood components (marine and flash flooding) can be considered the most relevant along the coast, with generally medium risk values. The long-term flood component (SLR) only affects low-lying areas, with the Ebro delta being the most important. Results indicate that the Maresme comarca is the most sensitive region to storm-induced components in the Catalan coast.Las zonas costeras concentran un elevado número de valores tanto naturales como socio-económicos que las hacen muy vulnerables a los efectos potenciales de los riesgos naturales. Por ello, para llevar a cabo una gestión adecuada del riesgo se requiere un análisis holístico en el que se tengan en cuenta las múltiples componentes que determinan el riesgo. Esto se ha abordado con el uso del concepto de El Paisaje del Riesgo Costero, que puede definirse como el riesgo integrado de las zonas costeras del resultado de la acción e interacción de los riesgos naturales y/o humanos inducidos sobre los valores y bienes existentes. La tesis presenta una metodología para la evaluación del riesgo de erosión e inundación costera a escala regional en el que se considera el análisis integrado de los principales procesos asociados a forzamientos que inducen erosión e inundación a diferentes escalas temporales (episódica, medio y largo plazo) así como un análisis de sus consecuencias socio-económicas. Esto se ha enmarcado dentro del modelo Source-Pathway-Receptor-Consequence (SPRC) en el cual el "pathway" se ha adaptado para representar cada riesgo considerando los diferentes procesos relacionados que actúan a diferentes escalas temporales. Para ello, cada componente (proceso) es evaluada individualmente y clasificada en una escala de intensidad que permite la integración y comparación de su importancia relativa a lo largo de la costa. La escala de intensidad para las componentes de erosión (episódica, medio y largo plazo), se consideran en terminos de como se ve afectada la playa para proveer la funcion de recreación y protección. Para la inundación, se utilizan diferentes variables que permiten caracterizar y evaluar cada una de sus componentes (riadas, inundación marina e inundación por la subida del nivel del mar SNM) clasificandolas en una escala de intensidad. Esto permite la evaluación de la contribución individual así como la relativa al riesgo final. Las consecuencias de erosión e inundación se determinan por separado teniendo en cuenta sus impactos más relevantes. En el caso de erosión, se consideran valores socio-económicos de las dos funciones costeras analizadas. Luego, las componentes de erosión se combinan en una matriz de riesgo, que proporcionan valores del riesgo para diferentes objetivos de gestión costera (i.e. recreación y protección). En el caso de la inundación, las consecuencias se evalúan mediante la caracterización de valores en exposición basados en un indicador que abarca cinco categorías (usos del suelo, población y vulnerabilidad social, sistema de transportes, negocios y servicios públicos). El riesgo total se expresa como la combinación de la amenaza y el valor de exposición. Todo ello es integrado a una escala adecuada de gestión, representada por el municipio. Esta metodología se ha aplicado a 219 km de playas a lo largo de la costa catalana (NE Mediterráneo español). Los resultados obtenidos indican que a pesar del buen estado general de la costa para proveer las funciones de recreación y protección en la actualidad, considerando una proyección futura para el año 2035 con las componentes de erosión a medio y largo plazo (erosión de base+erosión por SLR) el riesgo para proveerla se incrementa sustancialmente. Así, los municipios que en la actualidad tienen un desarrollo basado en el turismo, tendrán problemas para proveer un uso recreativo, y en la comarca del Maresme difícilmente se podrá proporcionar el nivel requerido de protección para el 2035. Además, las componentes episódicas de la inundación (riadas e inundación marina) pueden ser consideradas las más relevantes a lo largo de la costa con valores en general de riego medio. La componente de inundación a largo plazo (SNM) solo tiene efectos en costas bajas, siendo el delta del Ebro el más importante. Los resultados indican la comarca del Maresme como la región más sensible a las componentes provocadas por tormentas en la costa catalana.Postprint (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

A multi-component flood risk assessment in the Maresme coast (NW Mediterranean)

Coastal regions are the areas most threatened by natural hazards, with floods being the most frequent and significant threat in terms of their induced impacts, and therefore, any management scheme requires their evaluation. In coastal areas, flooding is a hazard associated with various processes acting at different scales: coastal storms, flash floods, and sea level rise (SLR). In order to address the problem as a whole, this study presents a methodology to undertake a preliminary integrated risk assessment that determines the magnitude of the different flood processes (flash flood, marine storm, SLR) and their associated consequences, taking into account their temporal and spatial scales. The risk is quantified using specific indicators to assess the magnitude of the hazard (for each component) and the consequences in a common scale. This allows for a robust comparison of the spatial risk distribution along the coast in order to identify both the areas at greatest risk and the risk components that have the greatest impact. This methodology is applied on the Maresme coast (NW Mediterranean, Spain), which can be considered representative of developed areas of the Spanish Mediterranean coast. The results obtained characterise this coastline as an area of relatively low overall risk, although some hot spots have been identified with high-risk values, with flash flooding being the principal risk process.Peer Reviewe

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 Reviewe

Erosion consequences on beach functions along the Maresme coast (NW Mediterranean, Spain)

A methodology to analyse the influence of erosion on beach functions at a regional scale is presented. The method considers erosion hazards at different timescales and assesses consequences by evaluating impacts on recreation and protection functions. To provide useful information to decision makers for managing these functions, hazard and consequences are integrated at the municipal level within a risk matrix. This methodology is applied at the Maresme, a 45-km sandy coast situated northward of Barcelona, which supports a strong urban and infrastructure development as well as an intensive beach recreational use. Obtained results indicate differentiated erosion implications along the region, depending on the management target considered. Thus, southern municipalities are more prone to erosion affecting the protection function of the beach and leisure use by the local population, whereas erosion will have a greater effect on foreign tourism in the northern municipalities. These results highlight the necessity to employ an articulated erosion risk assessment focusing on specific targets depending on the site in question. This methodology can help coastal managers to adopt tailored measures to manage erosion impacts towards specific goals, in a more efficient and sustainable manner.Peer Reviewe