1000-year of flood occurrences in Poland

Abstract

Knowledge about the frequency, intensity, and genesis of floods during historical periods in river basins worldwide is limited, mainly because the documentary evidence contains gaps in the coverage, quality and range of the necessary information. A comprehensive and reliable database is also time-consuming to create; therefore, there are few studies based on documentary evidence that analyze historical floods in various parts of the world for longer periods preceding the advent of instrumental measurements. Using a developed novel, reliable database of flood occurrences in Poland in the 11th–18th centuries and a list of floods for the 19th and 20th centuries based on a literature review, the frequency, intensity, genesis, and spatial distribution of floods in Poland in the last millennium were investigated. Analysis of results demonstrated the occurrence of 1,680 floods in Poland in the last millennium. The 18th century was the most abundant in recorded floods (356, 21%). Floods in the period 1001–1800 were most frequent in the Oder River basin (671, 55%), and in the Silesia region (553, 43%). Summer (JJA) was the most flood-prone season (46%), and therefore, rain was the main contributing factor to most of the flood occurrences in Poland (44%). According to the Mann-Kendall multi-temporal trend analyzing, overall, positive trends were more numerous for the periods of 1501–1700 and 1601–1800, whereas, more numerous negative for period of 1801–2000.