## 2 Materials and Methods
### Study Area  
The river Torysa flowing through the residential area of the city of Presov is part of the Hornad river basin (Figure 2). The area of the Hornad river sub-basin covers 4414 km\({}^{2}\) and is in the territory of three self-governing regions (Kosice, Presov, and Banska Bystrica regions). The Torysa river flows through the second-largest city in the basin-Presov with a population of 91,782 (last population census as of 31 May 2011). The population density in the city of Presov is 1303.06 inhabitants.km\({}^{-2}\) (Development Program of the City of Presov 2015-2020 with a view to 2025 [[https://www.presov.sk/download_file_f_php?id=734266](https://www.presov.sk/download_file_f_php?id=734266)]([https://www.presov.sk/download_file_f_php?id=734266](https://www.presov.sk/download_file_f_php?id=734266))). The area is in the flat or slightly rugged country of the Torysa flood plain, at an altitude of 231-275 m above sea level, composed of Quaternary, Neogene, and Paleogene sediments. The Quaternary is represented by fluvial sediments in the entire area of interest. It is dominated by gravel sediments, with the nature of alluvial sands and grits with a covering of clays and sandy loams. The Quaternary has a thickness of 5.0-8.0 m, in the valley part and 2.0-4.7 m at the terraced level [54]. The chosen location lies within the moderately warm climate zone T-1, which is characterized by long, warm, and dry summers, very short transition periods with warm to moderately warm springs and autumns, and moderately cold and dry to very dry winters with a short period of snow cover (50-80 d). The number of frost days per year is 120-130 [55]. The average annual air temperature is in the range of 8-9 \({}^{\circ}\)C (Climate atlas of Slovakia). The hydrological balance of the Hornad river basin (the territory of Slovakia) differs little from the values in the Danube administrative area. The average runoff in the sub-basin (period 1961-2000) is 210 mm and the average rainfall reached 701 mm (Management plan for the Hornad river sub-basin [[http://www.vuvh.sk/rsv2/default.aspx?pn=PMPV2](http://www.vuvh.sk/rsv2/default.aspx?pn=PMPV2) Hornad]([http://www.vuvh.sk/rsv2/default.aspx?pn=PMPV2](http://www.vuvh.sk/rsv2/default.aspx?pn=PMPV2) Hornad)). In July 2004, the eastern part of Slovakia was affected by extensive floods, which also affected the partial catchment of the Hornad river, which includes the Torysa river. The flood had a limited area and short time duration and by its manifestation, it ranked among extraordinary statistical significance. The total rainfall at the Presov climatic station was 195.6 mm in this period (26 July 2004-1 August 2004) and reached N = 1.087% compared to normal. In the catchment areas of Torysa and Sekcov, peaks corresponding to a 2-10-year flow were achieved. At the Presov (Torysa) water meter station on 30 July 2004, the peak reached 407 cm, Q = 140-m\({}^{3}\).s\({}^{-1}\), which represents a 10-year flow rate (SHMI, Floods in Eastern Slovakia in July 2004 [[http://www.shmu.sk/File/HIPS/Povodnova%20%20](http://www.shmu.sk/File/HIPS/Povodnova%20%20) situacia%20 na%20 vychode%20v%20 juil%20%202004.pdf]([http://www.shmu.sk/File/HIPS/Povodnova%20%20](http://www.shmu.sk/File/HIPS/Povodnova%20%20) situacia%20 na%20 vychode%20v%20 juil%20%202004.pdf)). The area affected by flooding due to extreme long-lasting rainfall hitting large areas of Slovakia was examined in 2010. The share of the Hornad river sub-basin in the declared levels of flood activity in 2010 was 17.51%, ranking it second behind the Bodrog river sub-basin with 28.09%. Figure 2: Study area—river Torysa flowing through the residential area of the city of Presov. In Slovakia, the first half of the hydrological year 2010 was very humid. The precipitation abnormal autumn and winter months of 2009, during which more significant precipitation conditions occurred in several regions of Slovakia, followed by the normal precipitation in March 2010, followed by the above-normal April and the extraordinary above-normal May 2010.