An international team of scientists, which included specialists from Masaryk University, the Academy of Sciences of the Czech Republic, and the Czech Hydrometeorological Institute, studied changes in the frequency and magnitude of floods over the last half millennium in Europe. Using historical sources and systematic hydrological observations, they analysed nine periods of increased flood activity.
The last such period, which was the richest in flood activity, occurred in the past three decades. In this period, floods were most frequent in summer. According to the researchers, these findings must be taken into account when developing flood-risk management strategies. This expansive historical overview of floods in Europe was published in Nature.
Amongst the periods richest in floods are 1560–80 in Western and Central Europe, 1760–1800 in most of Europe, 1840–70 in Western and Southern Europe, and 1990–2016 in Western and Central Europe. The scientists made this discovery by analysing more than one hundred long flood series from major European rivers. They reconstructed these series using data from different historical sources, such as chronicles, newspapers, and letters, as well as data from systematic hydrological observations.
Studying the history of floods helps specialists determine the extent to which climate variability and climate change affect flooding. Therefore, they studied the occurrence of floods in different years and examined their characteristics, magnitude, and impacts.
“The study demonstrated that in Europe, 1990–2016 was the flood-richest period in the last 500 years. But it differed from earlier periods of high flood activity in terms of extent, seasonality, and air temperatures. More than 50 percent of floods during the most recent flood period occurred in summer, which was significantly more often than in other flood-rich periods,” says Rudolf Brázdil, one of the study’s authors from the Faculty of Natural Sciences of Masaryk University and CzechGlobe, the Global Change Research Institute of the Academy of Sciences of the Czech Republic.
The study was also co-authored by two other Czech scientists, Monika Bělínová from CzechGlobe, the Global Change Research Institute of the Academy of Sciences of the Czech Republic, and Libor Elleder from the Czech Hydrometeorological Institute. These Czech scientists contributed data about floods on the Vltava, Labe, Ohře, Odra, Morava, Dyje, and Otava Rivers.
Data for better flood prediction
“Over the years, we have created a database containing data about weather and hydrometeorological extremes using documentary evidence for climate reconstruction and other climate history analyses. The objective of climate reconstruction is to create continuous precipitation and air temperature series, as well as flood chronologies,” says CzechGlobe’s Monika Bělínová, describing the goals of historical climatology and hydrology. She adds that highly accurate and detailed data provide the best foundations for forecasting.
This study published in Nature was therefore based on the work of other researchers from Masaryk University. “To assess the relationship between flood-rich periods and air temperature, a 500-year air-temperature series from Central Europe was used. This series was reconstructed based on documentary sources and using the datasets and know-how of the historical climatology and hydrology research group of the Department of Geography at MU’s Faculty of Natural Science,” adds Brázdil.