It went down in history as the "St. Mary Magdalene's Flood" – a massive flood disaster that engulfed large parts of Europe in 1342. Now, in a painstaking, years-long effort, historical sources have been analyzed and combined with modern hydrological knowledge to obtain a reliable picture of this natural disaster.
This revealed some surprises: The great flood of 1342 was not an isolated event, but a particularly devastating part of a series of 16 flood events lasting almost two years. A lesson can be learned for the future: Flood protection must not only consider individual extreme events. It must also be anticipated that several major floods will occur in quick succession.
Thousands dead, multiannual crop failures
More than a thousand entries from contemporary sources were analyzed to study the impact of the floods of this period. The project was led by TU Wien, with the participation of universities from across Europe. The historical records present a dramatic picture: "Many thousands of people died in the floods, from hunger and disease," says Andrea Kiss, a historian/medievalist and geographer at TU Wien, lead author of the study.
The economy of the entire continent was affected: trade routes were disrupted, and vital infrastructure was destroyed—for example, the Stone Bridge in Prague, which spanned the Vltava River before the construction of the now-famous Charles Bridge.
"Historical data show that it wasn't just a single flood event, but a whole series of events," says Günter Blöschl, hydrologist, team leader at TU Wien. Where historical records are incomplete, modern floods with similar conditions were selected to draw analogies. In this way, a comprehensive picture of flood history in space and time emerged step by step. "We can reconstruct month by month when which regions of Europe were affected," says Andrea Kiss. "This clearly shows that a series of flood events stretches like a string of pearls through the years 1341 to 1343. Not all equally devastating, not all in the same place, but all clearly connected".
Possible Causes of the Unusual Cluster
1342 was the year with the highest number of extreme flood events in the last 700 years, and 1343 is a close third. This cluster was no coincidence: The team found several possible factors that could have contributed to this extraordinary series of floods. Around 1340 and 1341, an unusually high number of volcanic eruptions occurred, including the Hekla eruption in Iceland. Sulfur-containing aerosols in the atmosphere can lead to cooling and alter large-scale circulation patterns.
At the same time, Arctic sea ice had already declined significantly since the mid-1330s, while solar activity in the 1330s-1340s was still relatively low. "The interplay of these factors could have contributed to intense low-pressure systems, prolonged rainfall, and thus the unusual series of floods." says A. Kiss. "This is extremely interesting for us today: We can draw important lessons about the interplay of climate and precipitation from events that occurred almost seven centuries ago," says G. Blöschl.
Furthermore, the St. Mary Magdalene's Flood confirms a finding that the TU Vienna team had already reached in another context: Flood events are not statistically independent of one another. They don't simply occur randomly like lottery wins; they can be statistically and causally linked. This means that even in modern risk planning, it must be considered that flood disasters cannot be viewed in isolation, but can always occur in rapid succession.
