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Number of concurrent coastal storms (Hs > 2 m) recorded across coastal basins (horizontal panels) within a ± 3-day window of an extreme rainfall event (P24h > 100 mm) in the rainfall source basin (y-axis). Numbers within each cell indicate the number of concurrent coastal storms observed for rainfall source basin-coastal sector combination.
Aguilera-Vidal, M, Sanuy, M, Jiménez, JA, (2026) Beyond localized hotspots: hazard connectivity in spatially compound rainfall-coastal storm events. Environmental Research Letters, 21, 144021, doi: 10.1088/1748-9326/ae8a69
Beyond localized hotspots: hazard connectivity in spatially compound rainfall-coastal storm events
Flood risk is usually assessed by considering where heavy rainfall and coastal storms occur together. However, this study shows that the same weather system can simultaneously generate severe impacts in geographically distant regions, creating new challenges for emergency response and risk management.
By analysing more than 40 years of rainfall, wave, and atmospheric data along the 1,600-km Spanish Mediterranean coastline, two distinct modes of hazard connectivity were identified. One forms a continuous corridor from northern Catalonia to central Valencia, where localized heavy rainfall is accompanied by widespread coastal storms affecting more than 600 km of coastline. The second links southwestern Andalusia with Catalonia, where the same atmospheric system produces heavy rainfall in southern Spain while simultaneously generating coastal storms hundreds of kilometres away. The study also identifies the large-scale weather patterns responsible for these contrasting behaviours.
The findings show that flood risk depends not only on where hazards occur, but also on how they are connected across space. This new perspective could improve regional flood forecasting, emergency planning, and climate adaptation, particularly as climate change is expected to increase the frequency and severity of extreme weather events.
Projected changes in compound flooding potential along the western Mediterranean coast. Map of the western Mediterranean basin showing projected changes in compound flooding potential, expressed as differences in the Compound Flooding Potential Index (CFPI), along the 1,600 km Spanish Mediterranean coastline for 2070-2100 relative to the 1970-2000 reference period. Inner symbols indicate changes driven by projected variations in rainfall, waves and storm surge, excluding SLR, whereas outer symbols show changes when SLR is included. Values represent the ensemble mean CFPI change across 17 CMIP5 model projections (see Table 1). Confidence levels (1: mixed/weak agreement (<60%); 2: moderate agreement (60-75%); 3: strong agreement (>75%)).
Jiménez, JA, Del Rosal Salido, J, Giaroli, F, Lira-Loarca, A, Ortega-Sánchez, M, Sanuy, M, Silva-Santana, M, Bermudez, M (2026) Sea-level rise is projected to reshape compound flooding potential in microtidal environments along the Spanish Mediterranean coastline. Communications Earth & Environment, 7, doi: 10.1038/s43247-026-03712-8
Future coastal compound flooding will be driven more by rising seas than stronger storms
A new study identifies sea-level rise as the main driver of future compound flooding along the Spanish Mediterranean coast. Compound flooding occurs when heavy rainfall coincides with high coastal water levels, increasing the severity of flood impacts.
Analyzing climate projections for more than 1,600 kilometers of coastline, it was found that changes in storm characteristics alone are unlikely to significantly increase flood risk. However, rising sea levels substantially increase the likelihood and impact of flooding when extreme rainfall and coastal water levels occur together.
The findings suggest that sea-level rise will play a dominant role in shaping future coastal compound flood risk, highlighting the need to incorporate its effects into long-term adaptation and coastal planning strategies.
Frequency of representative Synoptic Weather Patterns associated with compound events across all basins in Catalonia and in the northernmost basin over the periods (a) 1950–1973; (b) 1974-1997; (c) 1998-2022
Aguilera-Vidal, M, Sanuy, M, Ortego, MI, Jiménez, JA (2026). How compound flood drivers have changed over time in the Catalan coast (NW Mediterranean). Weather and Climate Extremes, 23, 100917, doi: 10.1016/j.wace.2026.100917
Study identifies strengthening rainfall–wave coupling as a driver of coastal flood risk
A new study shows that the risk of compound flooding caused by the combination of heavy rainfall and high waves has changed along the Catalan coast over the past 70 years. These hazards are becoming increasingly synchronized, particularly in northern Catalonia, leading to a higher frequency of extreme flooding events.
The study links this trend to changes in Mediterranean weather patterns that favor the simultaneous occurrence of intense rainfall and energetic waves. Northern Catalonia was identified as the most exposed region, with the highest probabilities of compound events.
The findings highlight the need to consider the growing interaction between multiple hazards when assessing coastal flood risk and developing climate adaptation strategies.
Median shoreline retreat rates calculated by the PCR model and Bruun rule-derived projections for different SLR rates during the 21st century for the SSP1-2.6 and SSP5-8.5 at Maresme (left) and Llobregat (right). Each data point represents a 10-year average, with dates indicating the center of the relevant 10-year interval. Solid lines indicate the best-fit relationships for each dataset, while the red dashed line represents the best linear fit to SSP5-8.5 PCR projection up to mid-century SLR rates.
Romero-Martín, R, Reyns, J, Dastgheib, A, Ranasinghe, R, Jiménez, JA (2026). Climate change-driven shoreline change along the Catalan coast (NW Mediterranean): A probabilistic approach for risk-informed coastal management. Coastal Engineering, 206, 104965, doi: 10.1016/j.coastaleng.2026.104965
Traditional coastal erosion model may overestimate future shoreline retreat along parts of the Catalan coast (NW Mediterranean)
Using an advanced probabilistic model that accounts for both SLR and changing wave conditions, it was found that the commonly used Bruun rule overestimated shoreline retreat by up to 70% at the Llobregat Delta under a high-emissions climate scenario. In contrast, projections from both approaches were similar for the Maresme coast.
The results suggest that simplified methods may not accurately capture future coastal change in all environments, particularly on low-sloping beaches. By incorporating local coastal characteristics and future hydrodynamic conditions, physics-based probabilistic models can provide more reliable projections to support coastal adaptation and resilience planning in a changing climate.
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