Documentary evidence of past floods in Poland in the 11th–15th centuries

The frequency, intensity and origin of floods in Poland in the 11th–15th centuries were assessed through analysis of all available documentary evidence. Intensity and origin of floods were estimated using the most well-known and reliable flood classifications for Europe (Barriendos and Coeur 2004; Brázdil et al. 2006; and Lambor 1954). The result indicated 166 flood occurrences in Poland in the 11th–15th centuries. The database of flood records showed that most of the floods in the historical sources were registered for the 15th century (61.4%). In addition, the Silesia and Baltic Coast region and Pomerania were the most vulnerable to flood events, each accounting for 33–34% of instances. The flood intensity estimated based on the Brázdil et al. (2006) classification, revealed that 77 of the recorded floods were above average or supra-regional. In turn, according to Barriendos and Coeur’s (2004) classification, 99 floods were extraordinary. The main cause of floods in Poland during the 11th–15th centuries (almost every second case of flood), was rain and its subtypes. Comparison of the results of this study against the occurrence of floods in neighboring countries (Germany, Czech Republic and Hungary) presents good spatial coherency. The results of this study provide the most comprehensive, updated and state-of-the-art inventory of floods in medieval Poland and should significantly improve the existing knowledge about this phenomenon in Central Europe. The output of this study once again confirms the capacity of documentary evidence to provide valuable and reliable knowledge about flood records for the pre-instrumental period. The work was supported by the National Science Centre, Poland, project No. 2020/37/B/ST10/00710. References: Barriendos, M., & Coeur, D, 2004: Flood data reconstruction in historical times from non-instrumental sources in Spain and France. Systematic, Palaeoflood and Historical Data for the Improvement of Flood Risk Estimation. Methodological Guidelines, edited by: Benito, G. and Thorndycraft, VR, Centro de Ciencias Medioambientales, Madrid, Spain, 29–42. Brázdil, R., Kundzewicz, Z. W., & Benito, G., 2006: Historical hydrology for studying flood risk in Europe. Hydrological sciences journal, 51(5), 739–764. https://doi.org/10.1623/hysj.51.5.739. Lambor, J., 1954: Klasyfikacja typów powodzi i ich przewidywanie. Gospodarka Wodna, 4, 129–131.