Llasat et al. (2024) Floods in the Pyrenees: a global view through a regional database

Identification

• Journal: Natural hazards and earth system sciences
• Year: 2024
• Date: 2024-10-07
• Authors: María Carmen Llasat, Montserrat Llasat-Botija, Erika Pardo, Raül Marcos-Matamoros, Marc Lemus‐Canovas
• DOI: 10.5194/nhess-24-3423-2024

Research Groups

• GAMA, Department of Applied Physics, Universitat de Barcelona, Spain
• IdRA, Water Research Institute, Universitat de Barcelona, Spain
• Andorra Research + Innovation, Sant Julià de Lòria, Andorra
• Non-Linear Physics Group, University of Santiago de Compostela, Spain

Short Summary

This study presents PIRAGUA_flood, the first systematic dataset of flood episodes (1981-2015) for the entire Pyrenees massif, revealing 181 events, 154 fatalities, a higher frequency in the eastern Pyrenees, and a slight positive trend of 0.84 events per decade associated with southern component atmospheric flow.

Objective

• To present the first systematic database of flood episodes covering the entire Pyrenees massif for the period 1981–2015.
• To analyze the spatial and temporal distribution and trends of flood episodes across the Pyrenees massif and its administrative regions.
• To characterize the weather types associated with these flood events.

Study Configuration

• Spatial Scale: Entire Pyrenees massif (49 850 km²), extending from the Atlantic Ocean to the Mediterranean Sea, encompassing 1803 municipalities across Spain (Catalonia, Aragon, Navarre, Basque Country), France (Nouvelle-Aquitaine, Occitanie), and Andorra.
• Temporal Scale: 1981–2015 (35 years).

Methodology and Data

• Models used:
  • Principal Component Analysis (PCA) with Varimax rotation for weather type classification.
  • Linear regression for trend analysis.
  • Mann–Kendall test for trend significance (p < 0.05).
  • synoptReg R package for synoptic classification.
  • Geographic Information Systems (GISs) (ArcGIS 10.4 and QGIS 3.10) for spatial analysis.
• Data sources:
  • PIRAGUA_flood database (created in this study, available at http://hdl.handle.net/10261/270351).
  • FloodHYMEX and INUNGAMA databases.
  • National Catalogue of Historical Floods (CNIH) for Spain.
  • Spanish Insurance Compensation Consortium (CCS) data (1996–2015).
  • Newspapers (La Vanguardia, El Heraldo de Aragón, Diario de Navarra) and government press releases.
  • SAFRAN analysis for precipitation data.
  • Central Reinsurance Company (CCR) and National Observatory of Natural Risks (ONRN) databases for France.
  • Météo France extreme rainfall records.
  • ERA5 reanalysis for mean sea level pressure and 500 hPa geopotential height (0.25° resolution, 30–60° N, 20° W–20° E).
  • CENMA-IEA and Ministeri d’Ordenament Territorial (Andorra).
  • Cartographic and Geological Institute of Catalonia (ICGC) and Eurostat GISCO for municipality data.
  • PIRAGUA (OPCC) delimitation in shapefile format.

Main Results

• The PIRAGUA_flood database, the first systematic and publicly available dataset for the entire Pyrenees massif (1981-2015), was developed, detailing 181 distinct flood events and 154 fatalities.
• The eastern Pyrenees (Catalonia, Andorra, Occitanie) experienced a higher concentration of flood events, with Catalonia recording the most (66 events), followed by Andorra (46) and Occitanie (36).
• Andorra showed the highest percentage of ordinary floods (67.4%), while Nouvelle-Aquitaine had the highest percentage of catastrophic floods (35.3% of its 17 events).
• Total compensation paid by the Spanish Insurance Compensation Consortium (CCS) for flood damage in the Spanish Pyrenees between 1996 and 2015 amounted to EUR 142.5 million (2015 values), with Navarre receiving the largest share (EUR 65.8 million).
• Aragon recorded the highest number of fatalities (97), largely due to the 1996 Biescas campsite disaster (87 deaths).
• A slight positive trend of 0.84 flood events per decade was observed for the entire Pyrenees massif (significant at 90%), primarily driven by ordinary and extraordinary floods.
• Regionally, only Nouvelle-Aquitaine exhibited a statistically significant positive trend of 0.34 events per decade (at 95%).
• Flood events show a seasonal pattern, with autumn maxima in Mediterranean-influenced regions and spring/summer maxima in Atlantic-influenced regions.
• Cross-border events (41 recorded, 34 international) are most frequent in autumn, often affecting Catalonia, Aragon, Occitanie, and Andorra simultaneously.
• Associated weather types are predominantly characterized by southern component flow over the Pyrenees, with a talweg over the Iberian Peninsula and a nearby depression (Atlantic or Mediterranean), fostering warm, humid air advection and instability.

Contributions

• Creation and public release of PIRAGUA_flood, the first systematic, comprehensive, and cross-border flood event database for the entire Pyrenees massif at a municipal scale (1981-2015).
• Detailed spatial and temporal analysis of flood events, including trends, across the entire massif and its constituent administrative regions in Spain, France, and Andorra.
• Characterization of synoptic weather types associated with flood episodes in the Pyrenees, linking them to regional flood patterns.
• Quantification of socio-economic impacts (fatalities, insurance compensation for Spain) at a regional and municipal level, highlighting areas of high vulnerability and exposure.
• Emphasis on the transnational nature of many flood events, underscoring the need for cross-border cooperation in flood risk prevention and mitigation.

Funding

• Interreg (grant no. EFA210/16), international cooperation project PIRAGUA.
• Spanish Ministry of Science and Innovation, C3RiskMed (grant nos. PID2020-113638RB-C22 and AEI/10.13039/501100011033).
• Flood2Now (Improvement of early warning systems for flood risk with past information and citizen data; PLEC2022-009403, MCIN/AEI/10.13039/501100011033).
• European Union NextGenerationEU/PRTR.
• Serra Húnter Programme of the Generalitat de Catalunya (for Raül Marcos-Matamoros).

Citation

@article{Llasat2024Floods,
  author = {Llasat, María Carmen and Llasat-Botija, Montserrat and Pardo, Erika and Marcos-Matamoros, Raül and Lemus‐Canovas, Marc},
  title = {Floods in the Pyrenees: a global view through a regional database},
  journal = {Natural hazards and earth system sciences},
  year = {2024},
  doi = {10.5194/nhess-24-3423-2024},
  url = {https://doi.org/10.5194/nhess-24-3423-2024}
}