Endless deluges. Sixteen floods and a devastated Europe

“Après nous, le déluge” – but in fact there had also been a deluge at the very beginning. Indeed, more than one, and literal ones at that, not metaphorical. And accompanied by a host of other apocalyptic events. “Après nous, le déluge” is the phrase attributed to Madame de Pompadour, spoken to lift the spirits of her lover Louis XV following the disastrous defeat inflicted by Frederick II of Prussia at the Battle of Rossbach. Some scholars, however, assert that it was Louis XV who directed the remark to his mistress, who died before him and was succeeded by Madame du Barry. In that interpretation, the metaphorical deluge was the French Revolution, during which Madame du Barry, the heir to the throne Louis XVI, and Queen Marie Antoinette were all guillotined. Historians later marked 14 July 1789—the storming of the Bastille—as the beginning of contemporary history and the end of the modern era, conventionally dated from 12 October 1492 with the arrival of Christopher Columbus in the Americas.

But the Middle Ages, in turn – which, according to a similar convention, are said to begin on 4 September 476 with the deposition of the last Western Roman Emperor, Romulus Augustulus, by Odoacer, King of the Heruli – do not, in reality, like all historical periods, have an abrupt end, even if it is useful to invent one in school textbooks. ‘The Autumn of the Middle Ages’ is the title of the famous essay in which, in 1919, Johan Huizinga explained that, in fact, as early as the 14th and 15th centuries, the world had already changed significantly, and modernity was on the horizon.

Many historians identify the turning point as the Black Death epidemic which, between 1346 and 1353, killed, depending on estimates, between one-third and two-thirds of the European population. The way in which Giovanni Boccaccio responded by creating the great epic of the Decameron – a sensational breakthrough for prose in the vernacular – is symbolic of the revolution whereby, by concentrating vast fortunes in the hands of the survivors, destroying ancient, closed castes, improving the balance between population and resources, and annihilating the old ‘intellectual mafia’ that had maintained Latin as a means of excluding the masses from culture – meant that, rather than annihilating the continent, that massacre served instead to remove the barriers that still kept it closed in on itself, setting in motion the whirlwind of progress that would bring an end to the Middle Ages and usher in the modern age. But shortly before that, there had been what a recent study has just termed ‘the flood of the millennium’, which devastated half the continent. And that was to be the major precursor to the upheaval that subsequently culminated in the Black Death.

Researchers at the Vienna University of Technology have now reconstructed, month by month, a series of sixteen devastating floods which, between 1341 and 1343, swept away centuries-old bridges and disrupted trade routes for months. The event that has remained most vividly in historical memory is what has been termed the Great Flood of Saint Mary Magdalene on 22 July 1342, so named in honour of the feast day on which it reached its peak, in the heart of the Holy Roman Empire. However, that was in fact only the most violent episode in a much broader sequence, even though accounts of other related events have remained scattered for centuries across thousands of medieval documents which, until now, no one had ever systematically collected or compared. It follows that the entire year of 1342, in particular, was, in terms of flooding, the most extreme recorded in Europe over the past seven centuries. Similar disasters followed one after another over the course of two years, with rivers such as the Rhine, the Danube, the Main, the Elbe and the Tisza bursting their banks repeatedly. Thousands of people died, either directly as a result of the floods or due to the famines and diseases that followed in their wake.

The research, now published in the journal Nature, was conducted by the Vienna University of Technology, with the participation of teams from universities across Europe. The study combines medieval theory, hydrology and climatology to reconstruct which regions were flooded between the end of 1341 and 1343, to what extent, and which climatic processes may have triggered them. Four of these sixteen major flood events have return periods – the statistical frequency with which a flood of a certain magnitude is expected to recur – ranging from 500 to 1,000 years. Building on the precedent set by the Flood of St Mary Magdalene, the study also assigns names linked to the liturgical calendar to other disasters: the Candlemas Flood, the Flood of St Mary Magdalene, the Flood of St James and the Flood of St Bartholomew.

The Candlemas flood, in February 1342, struck western and central Europe and swept away two-thirds of the historic Judith Bridge over the River Vltava in Prague, a structure dating back to the 12th century. The Flood of St Mary Magdalene, which occurred in July of the same year in southern Germany, destroyed bridges, mills and settlements along the Rhine and Main rivers, reaching a magnitude that occurs only once every 10,000 years. The Floods of St James and St Bartholomew, in 1343, mainly affected the Northern Alps and the Carpathians. The waters did not recede completely between one event and the next, causing prolonged health problems. Waterborne diseases, including what medieval documents describe as a ‘deadly haemorrhagic disease’ – probably dysentery – spread throughout the worst-affected areas. However, this clustering of floods within such a short period was in turn triggered by other catastrophic events of a different nature. Around 1340 and 1341, in fact, there were at least five tropical volcanic eruptions, along with a significant number of eruptions outside the equatorial regions, including the eruption of the Hekla volcano in Iceland in 1341.

Sulphur aerosols – microscopic particles released into the stratosphere (the layer of the atmosphere situated between 12 and 50 kilometres in altitude) by these eruptions – blocked some of the solar radiation and cooled surface temperatures in the Northern Hemisphere. As a result, the North Atlantic jet stream probably shifted southwards. In English, this strong, high-speed air current flowing from west to east in the upper troposphere is known as the ‘jet stream’, acting as one of the main regulators of European weather and climate. This led to intense cyclones accompanied by prolonged rainfall. However, the study also notes that reconstructions based on ice cores from the Barents Sea indicate a multi-year retreat of Arctic sea ice in that region from the mid-1330s onwards: a factor that may have reduced the albedo, i.e. the surface’s ability to reflect solar radiation. The temperature of the North Atlantic would have risen, and the combination of warmer waters and volcanic cooling would have favoured more frequent and intense cyclones. Hence, intense low-pressure systems, prolonged rainfall and the unusual series of floods.

But why, of so many disasters, has only the Maddalena flood survived in the collective memory? The study suggests several possible causes. Following the floods of July 1342, the local authorities in the affected German towns installed flood markers and commemorative plaques on iconic buildings, thereby institutionalising the memory of that specific event in those regions. Other floods, such as the Candlemas flood in Prague, left no similar physical traces. Furthermore, the surviving medieval documents show an uneven geographical distribution, with a higher density in the central regions of the Holy Roman Empire, and the chronicles tended to treat floods occurring after the first great flood as continuations of the same disaster.

However, this is not merely a historical reconstruction. The study compares those sixteen medieval flood events with modern floods that occurred between 1960 and 2020, selected for their similarity in terms of the area affected, seasonality and intensity. The results place the medieval sequence on a par with the major European floods of 1999, 2002, 2005, 2006 and 2013, as well as a dozen smaller-scale floods, all of which occurred within a period of less than two years. Large-scale flood events, more extreme than those of recent decades, are therefore possible and could recur, but current flood risk management is not necessarily equipped to deal with them, at a time when climate projections indicate an increase in cyclones in Europe, as well as in episodes of heavy rainfall caused by the rapid rise of warm, humid air masses.

But shortly before the great flood, there had in fact been another flood. A series of torrential downpours destroyed the harvests of 1315, 1316 and 1317 across the European continent, causing what is now known as the Great Famine. Preceding the Flood of Mary Magdalene and the Black Death, it began in the spring of 1315, with incessant rainfall which, in May, June, July and August, flooded and caused the fields of wheat, rye and oats – which were intended to feed tens of millions of people – to rot before harvest. The worst food crisis in medieval European history lasted until 1322, killing between 10 and 25 per cent of the population in some towns and leaving a demographic and social scar that would be exacerbated three decades later by the arrival of the Black Death.

As the English chronicler John of Trokelowe, a monk at the monastery of Saint Albans, wrote, May 1315 was ‘rainster than any memory’. He was not exaggerating. A 2020 study published in the journal Communications Earth & Environment, conducted by researchers at Columbia University, used the Old World Drought Atlas – a database compiled from tree rings – to establish that the three growing years preceding the famine, between 1314 and 1316, were the fifth wettest ever recorded in Europe between 1300 and 2012. 1315 was, in fact, the wettest year of that period spanning over seven centuries. 1314 was the second wettest year. Not only did the excessive moisture in the soil prevent the grains from germinating before mould destroyed them, but harvesting became impossible. Even the plants that survived the excess water could not be cut, bound and stored without the wet straw immediately rotting. Wheat crop losses in north-western Europe in 1315 are estimated at between 60 and 70 per cent compared with a normal year. Between 1315 and 1316, the price of wheat tripled in northern France, and that of oats increased fivefold. Real wages plummeted to historic lows.

But the crisis was not limited to wheat. As damp straw could not be stored as fodder, livestock – weakened by the scarcity of forage – became vulnerable to disease. The Great Cattle Plague, an epizootic disease that spread throughout Western Europe, reduced sheep and cattle populations by up to 80 per cent in some regions. The collapse of livestock farming eliminated not only a source of protein but also the draught power needed to plough the fields, exacerbating the problem for subsequent harvests. Consequently, access to staple foods became impossible for large sections of the urban and rural population. Here too, it was not an isolated climatic event. The Great Famine coincided with the onset of the transition from the Medieval Warm Period – a phase of relatively high temperatures lasting approximately from 950 to 1250 – to the Little Ice Age, a period of prolonged cooling that would last until the mid-19th century. This shift entailed a decrease of just half a degree Celsius in average summer temperatures across northern Europe, but it substantially altered atmospheric circulation patterns, resulting in cooler, wetter summers and a shorter growing season. In Ypres and Bruges, the hardest-hit cities in the Netherlands, urban mortality rates reached 20–25 per cent. Southern England lost between 10 and 15 per cent of its population, northern France 10 per cent, the Flemish chronicler Lodewijk van Velthem wrote in 1315 that there was no more room in the cemeteries of Brabant, and records show that even life expectancy at birth for the English royal family fell from 35.28 years in 1276 to 29.84 years.

Desperation gave rise to extreme reactions. Reports of children being abandoned, theft, the consumption of dogs and horses, and rumours of cannibalism appeared in news reports from various regions. Some historians have suggested that the famine may have inspired the story of Hansel and Gretel, whose parents abandon them in the forest because they can no longer feed them. Social order collapsed: exorbitant prices for basic foodstuffs sparked class conflicts and destabilised political structures throughout the affected region, from Poland to the Alps. Recovery was slow and incomplete. The rains ceased in the summer of 1317, but seed stocks had run out and livestock had been decimated. Supplies stabilised between 1322 and 1325. It took until around 1500 for the population to return to pre-crisis levels, a process slowed by the arrival of the Black Death in 1347.

Moreover, a study by the University of Cambridge suggests that the epidemic may also have been fuelled by a tropical volcanic eruption which, in 1345, is thought to have altered the climate, forcing a reorganisation of trade routes that would have facilitated the spread of the disease. Here too, therefore, there were harsher winters, short and rainy summers, and a series of poor harvests from 1345 to 1349. Contemporary chronicles describe cloudy skies and unusual temperatures – a scenario that led to widespread famine and extraordinary pressure on food supplies across the continent. Faced with scarcity, Italian urban elites turned to their international trade networks. In particular, the maritime republics organised the procurement of wheat from the Black Sea region, which was under the control of the Mongol Golden Horde. Via routes crossing the Black Sea to the main Mediterranean ports, the wheat made up for the lack of local resources and stabilised European markets.

The memory of the siege of the Genoese colony of Caffa in Crimea remains etched in the collective memory: in 1346, Mongol catapults bombarded it with the corpses of plague victims, sparking the outbreak that would subsequently spread by ship throughout the Mediterranean. Setting aside this extreme event, wheat transported by ship nonetheless became a haven for fleas infected with the bacterium Yersinia pestis, which can survive for days or even weeks in dry, dark environments, feeding on the debris found in wheat shipments. Once the grain arrived in Western ports, the fleas found new hosts among urban rodents, and from there the infestation spread to humans.