Recurring flood distribution patterns related to short-term Holocene climatic variability.

Area of Science:

• Paleoclimatology
• Hydrology
• Quaternary Science

Background:

• Holocene climate variability is well-documented, but its influence on extreme river flood timing and distribution remains unclear.
• Understanding past flood dynamics is crucial for predicting future hydrological changes.

Purpose of the Study:

• To reconstruct centennial-scale Holocene flood episodes in Europe and North Africa using a meta-analysis of dated flood units.
• To establish the relationship between past climate variability and the frequency and timing of extreme river floods.

Main Methods:

• Meta-analysis of over 2000 radiometrically dated flood units.
• Reconstruction of centennial-scale Holocene flood episodes.
• Correlation of flood data with paleoclimate indicators such as solar irradiance and North Atlantic Oscillation (NAO) phases.

Main Results:

• A general increase in flood frequency observed after 5000 calibrated years Before Present (cal. yr BP), linked to weakened zonal circulation and increased winter insolation.
• Multi-centennial flood phases in the UK and Central Europe correlate with periods of minimum solar irradiance, showing increased frequency over the last millennium.
• Western Mediterranean flood episodes synchronize with negative NAO phases, contrasting with patterns in the Eastern Mediterranean.

Conclusions:

• The long-term flood record reveals complex, interconnected climate-flood relationships across geographically distinct regions.
• This study provides a new framework for understanding and predicting future spatial changes in river flood frequency.
• Holocene climate variability has demonstrably impacted extreme river flood regimes.