Compound hydrometeorological risks on the Spanish Mediterranean coast in face of climate, environmental and social change

The effect of compound events, during which different climatic hazards such as surges, waves, heavy rainfalls, and flood episodes simultaneously or consecutively occur, may amplify the impacts from those same events occurring separately. Despite of this, their combined action is seldomly considered when assessing the impact of extreme events, with most of studies considering both types of hazards as they were univariate. This is also extendable to the development of risk management and adaptation strategies, where the different groups of hazards and their main influence zone are addressed separately. The differential treatment of these types of events allows us to analyze the possible impact of climate change in each of its parts. In Spain, the hydrometeorological disasters suffered in recent years, such as the Gloria and Filomena storms, the serious flash floods produced in Alcanar, or the current floods produced by the Ebro River and its tributaries, are in line with the effects of the climate change. Greater intensification is observed in some of the drivers. At the same time, there is a decrease in the tolerance limits, which entails a possible increase in risk. This is a notable problem on the Spanish Mediterranean coast, where exposure is increasing, both due to the increase in population and the assets exposed. The improvement of early warning systems has led to a decrease in vulnerability, but the uncertainty in the objective forecast that responds to the “when-where-how much” of a compound hydrometeorological event may be increasing.

In this framework the present contribution deals with the strategy to cope with these hydrometeorological compound events in the NE of Spain to characterize their remarkability by assessing their impact in terms of induced damages and required risk management measures; to identify the contribution of climatic and societal drivers to the impact for each type of events; and to assess the future coastal risk from compound events under climate change. This contribution has been developed into the Spanish project C3RiskMed (PID2020-113638RB-C21 and C22).