Exploring the mitigation of compound events in Barcelona: Urban water scarcity, flood risk and reduction of surface temperatures through water-sensitive urban design

Climate change is bringing with it situations where droughts coexist with periods of extreme rainfall in many regions of the world. Surface temperatures are increasing due to more frequent drought periods. In urban areas, the rise in surface temperatures also contributes to the heat island effect. In this context, the article explores the implementation of water sensitive urban design, which helps to mitigate water scarcity, reduce surface temperatures and cut rainwater runoff in the city of Barcelona. The approach entailed a major study, covering five-year records of surface temperatures in water sensitive urban design construction systems, and infiltration coefficient quantifications of the most characteristic materials used in rainwater runoff infiltration construction systems. This paper is also based on two floodable areas of Barcelona. The urban morphology of these areas varies. Within them, extreme compound events currently coexist. The most notable is extreme drought, for which urgent water supply restrictions have been implemented in Barcelona. Different scenarios and common parameters in calculations of water harvesting and rainwater infiltration will lead to decisions to implement green infiltration construction systems (nature-based) or blue solutions, depending on the hydrological balance in the study area. The last forecast of rainwater reduction and floods for Barcelona Municipality, according to the Fifth Assessment Report (AR5), was included in the procedure to check the durability of possible solutions. The AR6 forecast for Barcelona Municipality has not been published yet. • Barcelona is currently affected by compound events (water scarcity, floods and high temperatures). • WSUD can mitigate compound events in areas of Barcelona with different urban morphology. • The approach entailed a major study, covering five-year records of surface temperatures of built WSUD in Barcelona. • The methodology includes hydraulic conductivity quantifications of characteristic materials to build WSUD in Barcelona.