The cascading effect of wildfires on flood risk: a study case in Ebro River basin Spain
Abstract. Climate change increases the risk of wildfires and floods in the Mediterranean region. Yet, wildfire hazards are often overlooked in flood risk assessments and treated in isolation even though they can amplify floods. Indeed, by altering the hydrological response of burnt areas, wildfires can lead to increased runoff and cascading impacts. This study aims to comprehensively assess flood risk using a multi-criteria GIS-based approach, considering both current conditions and future scenarios for the Ebro River basin in Spain in the year 2100. More specifically, this study investigates future flood risk under the Shared Socioeconomic Pathways (SPP) 1-2.6 and SSP5-8.5 scenarios, taking into account projected socio-economic conditions and the cascading impact of wildfires. An Analytical Hierarchy Process (AHP) approach is employed to assign weights to various indicators and components of flood risk, based on insights gathered from interviews with seven experts specializing in natural hazards. Results show that the influence of wildfires on baseline flood risk is not apparent. Under the SSP1-2.6 scenario, regions with high flood risk are expected to experience a slight risk reduction, regardless of the presence of wildfires, due to an expected substantial development in adaptive capacity. The highest flood risk, almost double compared to the baseline, is projected to occur in the SSP5-8.5 scenario, especially when considering the cascading impacts of wildfires. Therefore, this research highlights the importance of adopting a multi-hazard risk management approach, as reliance solely on single-risk analyses may lead to an underestimation of the compound and cascading impacts of multi-hazards.
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