Nature-Induced Disasters
Persistent rainfall in the Gotthard region and the neighbouring areas to the east led to devastating floods at the end of September 1570. In the canton of Uri, almost all the bridges were torn away and the mule track over the Gotthard was so badly damaged that local residents had to rebuild it at great expense. The picture shows the disaster in the Maggia Valley (Canton Ticino): Large timbers and uprooted trees dammed the Maggia below Mogno. After breaking through further south, the river destroyed all the roads and bridges in the valley, sweeping away dozens of houses, 14 mills and 75 haystacks and flooding large areas of cultivated land. One person was killed (Pfister 1999: 233).
Reports on floods have been handed down in chronicles since the Middle Ages, and later also in weather diaries and in the form of flood marks. Most chroniclers compared the magnitude of a flood with corresponding older events. Where possible, they used the markers on bridges and buildings that recorded previous floods as a benchmark . In the anonymous "Chronicle of the Wars of Milan" from Basel, for example, we read about the flooding of the Rhine in Basel in 1511: "In 1511, on Saint Mary Magdalene's Day [22 July 1511], the Rhine in Basel became so great that the guilds called servants and offered them by oath to carry the salt in the salt house from the lower boxes to the upper ones. Then the river grew so fast that it was said to have happened, as had happened 31 years earlier [1480] in the water grotto. And it is said that some dry yokes on the river bridge were swept away, but they remained. And the river went to the Schifflüten pfyler, [...]" (translated from German). Based on the pillar of the Basel Rhine bridge decorated with an oriel and a shield, it can be estimated that the river was about as high on 1 August 1511 as it was on 13 June 1876.
From 1641 onwards, the level of major floods was documented at the so-called Schönbein House, Oberer Rheinweg 93 in Kleinbasel. Daily water level measurements are available from 1808, supplemented by discharge measurements from 1908, so that cross-references can be made between the flood marks and the descriptions. The largest floods of the Rhine could be reconstructed from 1268 onwards.
We know very little about severe (winter) storms in Western and Central Europe before the official measurement network began in 1864, because narrative reports in documentary data have hardly been taken into account. The data for Switzerland has also only been analysed selectively. What is known is that the hurricane "Prisca" on 18 January 1739, which has also been documented several times in Euro-Climhist, left a wide trail of devastation through France, south-west Germany and Switzerland. "Prisca" was the climax of a series of storms that was unique in Western and Central Europe in terms of its duration and intensity. Both were comparable to hurricane "Lothar" on 26 December 1999, as was the damage caused to forests and buildings Nevertheless, this event was omitted from the official chronicles. The reason could be that the modest public funds were nowhere near enough to cover even a small part of the enormous damage caused to buildings and crops. Instead, the canton of Zurich organised a public day of prayer in which at least one member of each household had to participate (Pfister et al. 2010). Numerous storms similar to "Prisca" and "Lothar", which caused significant damage to buildings and forests, are documented in Euro-Climhist. At an international level, data on storms in the Baltic Sea region is gradually being incorporated through a cooperation project with the University of Tallinn (Estonia).
Avalanches were not documented in detail in the sources until relatively late, not least because there was less written documentation in remote Alpine valleys than in urban areas. Although the first reports of destructive avalanches in Switzerland date back to the High Middle Ages, they are only really detailed from around the middle of the 18th century. Somereports were only written down on the basis of accounts by third parties. Records could be random individual observations - such as the Geneva naturalist Horace-Bénédict de Saussure (1740-1799) describing an avalanche in Amsteg (UR) in 1795 - or accounts by local experts with a broad knowledge of avalanches. Father Placidus Spescha (1752-1833), who initially grew up as a shepherd boy in Trun (GR) before receiving a monastic education in Disentis and Einsiedeln, occupies a special position. He undertook numerous first ascents in the region as a co-operator in several parishes in the Vorderrhein region. His processing of third-party accounts of the catastrophic avalanche winters of 1749 and 1808 as well as his eyewitness accounts of 1817 reveal an excellent understanding of the causes and course of avalanches; indeed, he also suggested the establishment of model Alpine villages in order to reduce the risk of avalanches for the population (Rohr 2014).