Analysis of flood compound events in the Andalusian Costa del Sol. A ClimEmpower Case Study

ABSTRACT

Coastal urban areas, particularly those in the Mediterranean coast, face an increasing probability of compound flooding into both current and projected climate change conditions (Bevacqua et al, 2019). In the Costa del Sol Occidental region of southern Spain, multi-hazard flood events—encompassing pluvial, coastal, and fluvial hazards—interact to produce significant impacts on populations, economies, and ecosystems. Research (IPCC, 2023; Zscheischler et al., 2018) highlights that the combined effects of multiple hazards on human and economic assets often exceed the sum of their individual impacts. This interplay results in greater flood depths and wider extents than those caused by single hazards occurring independently.
Despite these challenges, there is a lack of understanding and comprehensive tools in the region that account for the interdependencies of these hazards, particularly the compounding effects of pluvial flooding combined with coastal hydrodynamics. The aim of this research is to fill this gap by developing a multi-hazard risk model that takes into account the  interplay among pluvial flooding, coastal inundation, and the influence of ephemeral rivers in the region.
This study is part of the EU-funded ClimEmpower project, which focuses on enhancing resilience in five Mediterranean regions that are highly vulnerable to climate risks. ClimEmpower aims to provide tools, datasets, and indicators to address climate risks, enabling stakeholders to make more informed decisions regarding climate adaptation strategies.
The case study focuses on the Costa del Sol, a region located in the province of Málaga (Andalusia) in southern Spain. It encompasses 11 municipalities covering a total area of approximately 800 km² and distributed along more than 100 km of coastline. The case of Costa del Sol will develop an integrated approach that combines 1D/2D sewer modeling (MIKE Urban) with coastal hydrodynamic simulations (MIKE Zero), addressing both pluvial and coastal flooding mechanisms under both present and future climate scenarios using a loosely-coupled approach. 
The research will also assess the probability of occurrence of compound flooding events and will update the IDF curves, which are crucial for designing urban drainage systems and planning flood mitigation measures. To achieve this, high-resolution pluviometric data (sub-hourly data) was requested to authorities such as Spanish Meteorological Agency (AEMET), the basin Authority and the Andalusian Environmental Information Network (REDIAM).
A key challenge in this study regards data collection. Sewer network data is often incomplete or unavailable due to the management of different water utilities across the 11 municipalities of the study area. To overcome these data gaps, the study will apply a gap-filling methodology developed under the EU-funded ICARIA project (Moumtzidou et al., 2024). Additionally, the project will develop a social media crowdsourcing methodology to collect information about events that will be used to calibrate the models.
This research is expected to provide local authorities with essential tools for flood risk management and climate adaptation, empowering them to design more resilient urban environments and flood management strategies to address increasing compound events.

AKNOWLEDGMENTS

This research is part of the ClimEmpower project, funded by the Horizon Europe program of the European Union under Grant Agreement No.101112728 (https://cordis.europa.eu/project/id/101112728/es).