Llasat (2021) Floods evolution in the Mediterranean region in a context of climate and environmental change

Identification

• Journal: Cuadernos de Investigación Geográfica
• Year: 2021
• Date: 2021-02-12
• Authors: María Carmen Llasat
• DOI: 10.18172/cig.4897

Research Groups

• Meteorology Research Group, Department of Applied Physics, University of Barcelona, Barcelona, Spain

Short Summary

This paper synthesizes the state of the art on flood evolution in the Mediterranean region under climate and environmental change, concluding that flash floods are increasing due to land-use changes and increased vulnerability, with future impacts expected to rise due to global changes in catchments and heavy rainfall in the northern part of the basin.

Objective

• To synthesize the current understanding of flood evolution, trends, and projections in the Mediterranean region, considering the complex interplay of changes in hazards, vulnerability, exposure, and coping capacity under climate and environmental change.

Study Configuration

• Spatial Scale: Mediterranean region, with specific examples from southern France, Barcelona Metropolitan Area, Spain, Po river (Italy), Greece, Catalonia, Valencia, and the MENA region.
• Temporal Scale:
  • Historical analysis: From 14th century (Catalonia) and 1500 (Europe) up to 2016.
  • Recent trends: Primarily 1958-2018, with specific periods like 1980-2018 (fatalities), 1960-2010 (European floods), 1996-2011 (NE Spain), and 1989-2015 (Iberian Peninsula).
  • Future projections: Short-term (2020s), mid-term (2050s), and long-term (2080s, up to 2100).

Methodology and Data

• Models used:
  • SAFRAN reanalysis
  • ISBA land surface model
  • Lisflood distributed hydrological model
  • EURO-CORDEX (Coordinated Downscaling Experiment over Europe) climate projections
  • Regional climate models (from EURO-CORDEX project)
• Data sources:
  • Synthesis of main studies and recent bibliography on flood trends.
  • First Mediterranean Assessment Report (MAR1) by MedECC.
  • Historical flood series from archives and press.
  • Daily discharge data series (e.g., 171 series in southern France).
  • Land cover data (CORINE database, 1990-2018).
  • MEFF (Mediterranean Flood-related Fatalities) database (1980-2018).
  • EUFF (European Flood Fatalities) database (1980-2018).
  • IPCC reports (SREX, AR5, SR1.5).
  • 5-minute precipitation series.
  • Socioeconomic scenarios (population, urbanization, Gross Domestic Product).
  • Statistical tests: Mann-Kendall test, quantile regression method.

Main Results

• Floods in the Mediterranean region are predominantly flash-flood events.
• A positive trend of flash floods in the past is observed, primarily attributed to land-use changes and increased occupation of flood-prone areas (high confidence).
• An increase in convective precipitation may also contribute to this positive trend in recent periods in some regions (low confidence).
• Vulnerabilities to water-related hazards are expected to be influenced by future regional socioeconomic conditions (medium confidence).
• Flood impacts are projected to increase across the Mediterranean, mainly due to global changes in catchments (land use, vulnerability, exposure) and increased heavy rainfall in the northern part of the basin (medium confidence).
• The Mediterranean region has warmed by 1.4 °C compared to the pre-industrial period, which is 20% higher than the global average. Sea surface temperature increased by 1.3 °C between 1982 and 2019.
• Future climate projections suggest a general reduction in precipitation and runoff, but extreme rainfall is likely to increase in the northern basin and decrease in the southern basin.
• Projections indicate a decrease in flood hazards in some Mediterranean rivers (e.g., southern Spain) and an increase in others (e.g., Ebro river) by the end of the 21st century.
• The probability of high-impact flood events will increase with rising temperatures, considering future rainfall and socioeconomic scenarios.
• No significant trend is observed in upper extremes of daily precipitation, but a small trend of increased convective precipitation concentrated in fewer events was found in northeast Spain (1996-2011), consistent with local flash flood increases.

Contributions

• Provides a comprehensive synthesis of the state-of-the-art regarding flood evolution in the Mediterranean region, integrating findings from major reports (MedECC) and recent scientific literature.
• Highlights the complex, multifactorial nature of flood risk, emphasizing the interplay of climate change, environmental change (especially land use), vulnerability, exposure, and coping capacity.
• Distinguishes between trends in riverine floods (often decreasing in large basins) and flash floods (showing an increasing trend linked to anthropogenic factors).
• Addresses methodological challenges in flood trend analysis, including data heterogeneity, short series, and the distinction between flood hazard and flood impact.
• Offers insights into both historical (secular) and recent flood trends, as well as future projections, providing a holistic view of flood dynamics in the region.
• Advocates for integrated and holistic flood management strategies, aligning with international frameworks like the Sendai Framework and the EU Floods Directive, and emphasizes the need for improved risk awareness and international collaboration.

Funding

• Spanish project M-CostAdapt (CTM2017-83655-C2-R) of the FEDER/Ministry of Science, Innovation and Universities–AEI.
• Project EFA210/16/PIRAGUA, INTERREG POCTEFA 2014-2020.
• IAHS Panta Rhei working group ‘Changes in Flood Risk’.

Citation

@article{Llasat2021Floods,
  author = {Llasat, María Carmen},
  title = {Floods evolution in the Mediterranean region in a context of climate and environmental change},
  journal = {Cuadernos de Investigación Geográfica},
  year = {2021},
  doi = {10.18172/cig.4897},
  url = {https://doi.org/10.18172/cig.4897}
}