Introduction

The Mediterranean Basin lies in a transition zone between mid-latitude and sub-tropical atmospheric circulation regimes and is characterized by a complex morphology of mountain chains and strong land–sea contrasts that made of it a flood prone area, affected by frequent heavy rainfalls, windstorms and severe weather (Llasat, 2009), and a coastline subjected to storm-induced coastal hazards (e.g. Mendoza et al. 2011; Gervais et al. 2012). Moreover, a dense and growing human population, mainly concentrated at the coast, made of it a very vulnerable region that experience every year one or more natural disasters. 

Floods are the most frequent and among the costliest and deadliest natural disasters in the Mediterranean area (e.g. Blöschl et al., 2020), having produced more than 85 billion euros of damages since 1900 (UNISDR, 2015), and more than 1800 fatalities between 1981 and 2015 in six regions/countries (Vinet et al., 2019). In the NW Spanish Mediterranean coast, existing studies indicate an increasing trend in damages during the last decades (e.g. Jiménez et al. 2012; Llasat et al. 2014; Gil-Guirado et al. 2019). 

One of the intrinsic characteristics of flooding in coastal areas is that it can be induced by different climatic drivers such as storm surge, run-up, rainfall, and/or river flow, each of which may act individually but are often interconnected. Thus, although risk assessments in coastal zones usually consider the impact of sea hazards and climate drivers individually, they should instead be considered as the result of compounding events. Thus, recent analyses dealing with flooding risks in the coastal zone put emphasis on the importance of considering compound events, with some areas along the European coastline presenting a significant probability of occurrence such as the Mediterranean basin (e.g. Bevacqua et al. 2019).

From the risk management perspective, a key element to be characterized is the impact and damage induced by these compound events. In this sense, the magnitude of the impact and its associated risk must be attributed to the occurrence and intensity of involved hazards, and to the level of exposure and vulnerability of the affected areas (e.g. Kron, 2005; Visser et al. 2014; Koks et al. 2015; Zhou et al. 2017). The combination of different typologies of compounding hazards, with different probabilities of occurrence, and the spatial variation in vulnerability and exposure along the coastal zone, in particular along the Spanish Mediterranean, makes damage prediction not a straightforward task. In fact, the combination of the compound drivers (e.g. rainfall and coastal storms) with a given pattern of societal factors can exacerbate the climate-related hazards causing their impacts to be amplified relative to the impacts from those same events occurring separately or univariately.

This situation could be aggravated due to climate change, since observed rates of change in the Mediterranean Basin exceed global trends for most variables (Cramer et al., 2018). The recent First Mediterranean Assessment Report (MAR1, MedECC, 2020), shows that virtually all sub-regions of the Mediterranean Basin, on land and in the sea, are impacted by recent anthropogenic changes in the environment, and due to global and regional trends in climatic drivers (precipitation extremes, sea level rise, etc.) impacts will be exacerbated in the coming decades, especially if global warming exceeds 1.5 to 2°C above the pre-industrial level. Therefore, an adequate risk management of the Spanish Mediterranean coast would require assessing how the risk profile associated with the impact of compound events can change, both in magnitude and spatial distribution.

Based on these antecedents, the following main research needs have been identified, which will be addressed in this project