The contribution about a precipitation episode follows up on already published news from 21st June 2021 about a torrential rain in Dolní Bojanovice (CZ version) after which great erosions manifested themselves. The measured values are one of the greatest ever recorded by current automatic rain gauges.
A meteorological station with a rain gauge is located directly in Dolní Bojanovice and is used in particular for farming purposes. An evaluation of data from it gave us an idea about how extreme the rain had been. According to the measurements, precipitation was recorded between 5:30 and 8:15 p.m. CEST. When we look more closely, we see that there were two isolated precipitation episodes. During the first one that lasted from 5:30 to 6:30 p.m. CEST a total of 127 mm of rain fell in Dolní Bojanovice. After an approximately one-hour pause with only small precipitation totals another precipitation episode followed and further 42 mm of rain were measured. Over the three hours, 169 mm of rain fell there. The relevance of measured values was confirmed by the Czech Hydrometeorological Institute, which analysed the precipitation episode in detail. The quoted value is one of the highest ever recorded by current automatic rain gauges. There were other similar cases such as episodes from the Albrechtice – Žáry station (Bruntál district) on 31st May 2016 with 145.5 mm over 3 hours and an episode from the Olešnice station (Blansko district) on 15th July 2002 with 171.7 mm measured by a manual rain gauge. The precipitation fell largely in the course of 90 minutes. The latter episode sadly claimed 2 lives in Crhov and Hodonín municipalities. The measured data show that precipitation of similar intensities such as the one measured in Dolní Bojanovice is not exceptional in our country and represents a great risk to citizens. In this case the somewhat more limited scope of damage was due to more moderate topography and presumably also to the division of the precipitation episode into two parts.
Autor: Ing. Karel Drbal, Ph. D. (T. G. Masaryk Water Research Institute), Ing. Petr Janál, Ph. D. (Czech Hydrometeorological Institute)