Post-flood analysis of the flood from the rupture of the stone dam in Rudno nad Hronom on May 17, 2021

The study is aimed at reconstructing the course of the flood from May 17, 2021 breach of the stone dam in Rudno nad Hronom. Firstly, the volume of water in the reservoir before its breach was determined. The reservoir storage volume was estimated to be 14 807 m 3 . Then, we focused on the analysis of the hydrological regime in the wider Rudniansky Brook region. In order to derive the flood wave course from the rainfall, a series of 15-minute discharge from neighbouring water gauges measured by the Slovak Hydrometeorological Institute were analysed. In analysing the long-term trends of precipitation and temperature series we used data from the Banská Štiavnica meteorological station (period 1901–2020). In the second part, based on several field measurements after the flood event, we estimated the peak flows of floods from May 17, 2021 above the reservoir and under the reservoir. One hundred meters above the reservoir culmination reached 7.8 m 3 s -1 , under the reservoir it was between 80 to 100 m 3 s -1 . Finally, we reconstructed the course of the flood wave from the precipitation above the reservoir by hydrological analogy and by simple rainfall-runoff hydrological model NLC. The course of the breakthrough wave from the reservoir water just below the dam was determined to be triangular in shape so that the peak reached 90 m 3 s -1 and the volume was 15,000 m 3 .