| 20 May 2026
Storm Gloria (2020): joint probability of multiple flood hazards and compound events in a paradigmatic Mediterranean event
Abstract. Compound flooding arises when multiple hydrometeorological drivers co-occur and interact, amplifying risk beyond that expected from individual hazards. This work analyses Storm Gloria (19–25 January 2020, E Spain) as a paradigmatic compound event in the Mediterranean region. The coastal strip considered here extends for 1,609 km (from the French border to Málaga) and includes 8.4 million inhabitants in 12,167 km2. The event affected 770 municipalities caused 13 fatalities and four missing persons and generated about EUR2022 204 million in Spain's Insurance Compensation (CCS) payouts. The analysis combines daily precipitation (P₍₂₄ₕ₎; 662 AEMET rain gauges), maximum wind gusts (140 stations), and significant wave height (Hₛ; 50 SIMAR/CoExMed points) with municipality-level CCS compensation data. The event window is objectively defined (≥ 40 mm day⁻¹ at ≥ 2 stations), and hazard severity is mapped using operational thresholds (P₂₄ₕ = 40/100/200 mm; Hₛ = 2/5/7 m; wind gusts ≈ 70/90/100 km h⁻¹). Multivariate (river and sea flooding at the Tordera River mouth) and spatially compounding (flooding in the Júcar basin and sea storm in the Gulf of Jávea) cases are quantified through a two-sided conditional framework and copulas in two areas located in the northern and central part of the study region, respectively, whereas the temporally compounding case is evaluated empirically from heavy-rainfall episodes in the Segura basin, located in the southern part. Results indicate that, for the first case, the return period of the maximum recorded precipitation is estimated at 24 years; however, when the compound event – where wave action hindered the discharge of the Tordera River into the sea – is taken into account, the estimated return period increases to 85 years. In the second case, it goes from 1.5 years to 72 years, while in the third, the return period corresponding to the time sequence of three heavy rainfall events in the same basin, becomes 22 years. Overall, the largest compensation values tend to occur where hazard levels are highest, although exposure, vulnerability, and insurance coverage modulate the final impacts. This integrated workflow (objective event definition, threshold‑based hazard mapping, copula‑based joint recurrence, and impact linkage) provides a transferable, practice‑ready template for compound‑aware coastal risk assessment in Mediterranean settings and other coastal regions.
Competing interests: At least one of the (co-)authors is a member of the editorial board of Natural Hazards and Earth System Sciences.
Publisher's note: Copernicus Publications remains neutral with regard to jurisdictional claims made in the text, published maps, institutional affiliations, or any other geographical representation in this paper. While Copernicus Publications makes every effort to include appropriate place names, the final responsibility lies with the authors. Views expressed in the text are those of the authors and do not necessarily reflect the views of the publisher.
This work addresses an important topic related to the hazards associated with storm Gloria. Although the approach followed by the authors is outside my area of expertise, I have tried to provide a few suggestions to improve the flow and clarity of the manuscript. You are free to accept or reject my suggestions.
Lines 11-14: “The coastal strip…. Insurance Compensation (CCS) payouts”, these sentence are useless in the abstract. Consider to delete them.
Lines 18-24: “Multivariate…..” this sentence is too long and difficult to follow.
Lines 24-26: “Overall, the largest compensation values tend to occur where hazard levels are highest, although exposure, vulnerability, and insurance coverage modulate the final impacts”. This statement is not clear for a reader. How, your analysis is suitable for the hazard levels, mostly considering the return period that you obtained. This is important for a reader.
Line 35: substitute “affected” with “impacted”.
Line 99: check the term “realisations”, consider to change in “simulations”
Line 106: substitute “scope” with “area”.
Line 168 and Figure 2: I suggest to improve the synoptic description of the event, maybe using the MSLP from ERA5 with wind vectors at different time steps.
Line 185: this last sentence derives from a literature source or is it an outcome of your analysis?
Lines 315: From this point I suggest to reorganize the structure of the subsections. Avoid the subdivision in Type, Description and Probabilistic Analysis for the subsections.
Line 393: the Figure 7 reports only the points of raingauges and buoy, no results are mapped, the same for the Figure 8.
Line 605: The conclusion is very long, I suggest to summarize the outcomes of the study.