Europe's Worst Medieval Flood Was Part of 16-Event Sequence

A new study has shed light on Europe's worst medieval flood, known as St. Mary Magdalene's Flood of 1342, revealing that it was not a single event, but part of a sequence of 16 major flood events that occurred across Europe between late 1341 and 1343. This sequence of floods had a profound impact on the continent, causing thousands of deaths, both directly and indirectly through hunger and disease.

The year 1342 had the highest number of extreme flood events in the last 700 years, with four of the flood events between 1341 and 1343 having return periods of 500-1,000 years. The Magdalena Flood itself had a return period of 10,000 years based on documentary records and soil erosion patterns.

The floods had substantial socioeconomic consequences, including the destruction of infrastructure and settlements along major rivers, and extensive agricultural damage, contributing to widespread famine. In Prague, the flooding caused extensive damage to the Stone Bridge, which ultimately led to the construction of the Charles Bridge.

The cause of the flood sequence is believed to be a series of volcanic eruptions, combined with multi-annual Arctic sea ice retreat. This highlights the importance of considering the potential for multiple extreme floods to occur in succession when planning for future flood risk.

## Why it matters The study's findings have significant implications for flood risk management in Europe. The fact that 1342 had the highest number of extreme flood events in the last 700 years, and that four of the flood events between 1341 and 1343 had return periods of 500-1,000 years, suggests that the risk of successive extreme events is higher than previously thought. This highlights the need for quick and proactive risk strategies that account for the possibility of multiple extreme floods occurring within a short period.

The study's lead authors, from TU Wien (Vienna University of Technology), analyzed a wide range of evidence, including documentary records, historical sources, and comparisons with contemporary floods, to reconstruct the two-year flood sequence. The findings provide new insights into the characteristics of the largest documented historical floods in Europe and highlight the importance of considering the potential for multiple extreme floods to occur in succession.

## What happens next The study's findings will likely inform flood risk management strategies in Europe, with a focus on developing quick and proactive risk strategies that account for the possibility of multiple extreme floods occurring within a short period. This may involve the implementation of new flood mitigation measures, such as the building of levees and the implementation of land use planning, as well as the development of more effective emergency response plans.

The study's findings also highlight the need for further research into the causes of extreme flood events, including the role of volcanic eruptions and Arctic sea ice retreat. By better understanding the causes of these events, scientists and policymakers can work together to develop more effective strategies for mitigating their impacts.