We analyzed the runoff and its temporal distribution during the catastrophic flood events on river Gidra (32.9 km2 ) and Parná (37.86 km2 ) of the 7th June 2011. The catchments are located in the Small Carpathian Mountains, western Slovakia. Direct measurements and evaluation of the peak discharge values after such extreme events are emphasized in the paper including exceedance probabilities of peak flows and of their causal flash rainfall events. In the second part of the paper, plausible modeling mode is presented, using the NLC (Non Linear Cascade) rainfall-runoff model. Several hypothetical extreme flood events were simulated by the NLC model for both rivers. Also the flood runoff volumes are evaluated as basic information on the natural or artificial catchment storage. and Predložený príspevok analyzuje tvorbu a priebeh odtoku počas katastrofickej povodňovej situácie na Gidre (32,9 km2 ) a na Parnej (37,86 km2 ) dňa 7. 6. 2011. Povodia týchto tokov sa nachádzajú v Malých Karpatoch na západnom Slovensku. V príspevku sa kladie dôraz na priame zameranie a vyhodnotenie kulminačných prietokov po výskyte takýchto povodní. Diskutujú sa problémy vyjadrenia pravdepodobnosti prekročenia kulminačných prietokov a dažďov, ktoré ich spôsobili. V druhej časti príspevku je prezentovaný možný spôsob modelovania povodne jednoduchým zrážkovo-odtokovým modelom NLC. Daným modelom NLC sú následne simulované prietoky Gidry v stanici Píla a Parná v stanici Horné Orešany za extrémnej hypotetickej zrážkovej udalosti. Hodnotené sú objemy odtoku počas povodní, ako základný údaj pre reálny odhad ich prirodzeného alebo umelého zadržania.
In this paper we focused on the history of floods and extreme flood frequency analysis of the upper Danube River at Bratislava. Firstly, we briefly describe the flood marks found on the Danube River in the region of Bratislava, Slovakia, and provide an account of the floods’ consequences. Secondly, we analyzed the annual maximum discharge series for the period 1876–2012, including the most recent flood of June 2013. Thirdly, we compare the values of T-year design discharge computed with and without incorporating the historic floods (floods of the years 1501, 1682, and 1787 into the 138-year series of annual discharge peaks). There are unfortunately only a few historic flood marks preserved in Bratislava, but there are very important and old marks in neighbouring Hainburg and other Austrian cities upstream to Passau. The calculated T-year maximum discharge of the Danube at Bratislava for the period 1876-2010 without and with historic flood values have been compared. Our analysis showed that without incorporating the historic floods from the years 1501, 1682, and 1787 the 1000-year discharge calculated only with data from the instrumented period 1876- 2013 is 14,188 m3 s -1 , and it is lower compared to the 1000-year discharge of 14,803 m3 s -1 when the three historic floods are included. In general, the T-year discharge is higher throughout the whole spectrum of T-year discharges (10, 20, 50, 100, 200, 500-year discharge) when the three historic floods are included. Incorporating historic floods into a time series of maximum annual discharge seems to exert a significant effect on the estimates of low probability floods. This has important implications for flood managements and estimation of flood design discharge.
The aim of the paper is to study spatial and temporal changes in the magnitude, duration and frequency of high flows in the Danube basin. A hydrological series of the mean daily discharges from 20 gauging stations (operated minimally since 1930) were used for the analysis of changes in the daily discharges. The high flow events were classified into three classes: high flow pulses, small floods, and large floods. For each year and for each class, the means of the peak discharges, the number and duration of events, and the rate of changes of the rising and falling limbs of the waves were determined. The long-term trends of the annual time series obtained were analyzed and statistically evaluated. The long-term high flow changes were found to be different in three individual high flow classes. The duration of the category of high flow pulses is decreasing at 19 stations on the Danube and is statistically significant at the Linz, Vienna, Bratislava and Orsova stations. The frequency of the high flow pulses is increasing in all 20 stations. Also, the rising and falling rates of the high flow pulse category are increasing at the majority of the stations. The long-term trends of the selected characteristics of the small floods are very similar to the trends of the high flow pulses, i.e., the duration of small floods is decreasing, and their mean number per year is increasing. In the category of large floods the changes were not proved.
The extreme rainfall events in Central and East Europe on August 2002 rise the question, how other basins would respond on such rainfall situations. Such theorisation helps us to arrange in advance the necessary activity in the basin to reduce the consequence of the assumed disaster. The aim of the study is to recognise a reaction of the Uh River basin (Slovakia, Ukraine) to the simulated catastrophic rainfall events from August 2002. Two precipitation scenarios, sc1 and sc2, were created. The first of them was based on August’s precipitation from Ybbs (Austria), the second one was based on precipitation from south Bohemia. The rainfall-runoff model HBV-light was used to simulate average daily discharge. Observed daily precipitation in each August during the period 1990-1999 was replaced by these two scenarios and the daily discharges were simulated in Lekárovce gauging station. Peak discharges were computed from the daily averages according to the empirical relationship. In last step, a selection of the best theoretical distribution function of the annual maximum discharge was done using Qmax data series from the period 1931-2001. and Extrémne zrážkové udalosti z augusta 2002 v strednej a východnej Európe vyvolali otázku, ako by na podobné zrážkové situácie reagovali iné povodia. Takéto teoretické simulácie poskytujú možnosť eliminovať dôsledky extrémnych hydrologických situácií. Cieľom tejto štúdie je poznať reakciu povodia rieky Uh (Slovensko, Ukrajina) na prípadnú katastrofickú zrážkovo-odtokovú situáciu, aká bola v auguste 2002. Pre simuláciu extrémnych zrážkovo-odtokových situácií boli vytvorené dva katastrofické scenáre sc1 a sc2. Prvý scenár bol určený na základe zrážkových úhrnov nameraných v Rakúska (Ybbs) a druhý na základe zrážkových úhrnov nameraných v južných Čechách počas augusta 2002. Na simuláciu priemerných denných prietokov bol použitý model HBV-light. Merané denné zrážky v každom mesiaci august počas obdobia 1990-1999 boli zmenené podľa týchto scenárov. Následne boli simulované priemerné denné prietoky v stanici Uh-Lekárovce modelom HBV-light. Vrcholové prietoky boli počítané z denných priemerov vzhľadom na odvodené empirické vzťahy. V poslednom kroku štúdie bola vybratá najvhodnejšia teoretická distribučná funkcia maximálnych ročných prietokov použitím ročných Qmax z obdobia 1931-2001.
This paper deals with the formation of snowmelt-driven floods in two experimental microbasins located in Slovakia’s highlands (300-400 m a.s.l) near the town of Povazska Bystrica, Slovakia in March 2006. The first basin (Rybarik) encompasses an area of 0.119 km2 and is used primarily for agriculture; while the Lesný basin with its catchment area of 0.0864 km2 is characterized as a forested land. The maximal specific outflow from the Rybárik basin was observed on March 28, 2006, with 281.3 l s-1 km-2, peaking at 3 p.m. with 422 l s-1 km-2. In the Lesný basin, the maximum outflow was observed on March 29, 2006, with its peak of 523 l s-1 km-2 at noon. In the second part the long-term trend of snow water equivalent (SWE) modeled by the HBV-light rainfall-runoff model in the Rybarik and Lesny microbasins were evaluated. After the model verification, the daily values of SWE for the period 1965/66-2005/06 were calculated for Rybarik and Lesný microbasins. From the results it follows, that, after a temporal decline in the maxima of snow depth and of SWE in the 1990s, SWE started to increase in 2002 again. The historically highest values of SWE were simulated in both experimental microbasins in the winter season of 2005/06. and V príspevku je analyzovaná tvorba povodňového odtoku počas povodne z topenia sa snehu v marci 2006 na príklade dvoch experimentálnych mikropovodí lokalizovaných vo vrchovinovej časti Slovenska pri Považskej Bystrici (300–400 m n.m.), konkrétne z poľnohospodársky využívaného mikropovodia Rybárik (0,119 km2 ), a zo zalesneného mikropovodia Lesný (0,0864 km2 ). Maximálny meraný špecifický odtok z povodia Rybárik bol 281 l s-1 km-2 28. marca 2006 (vrchol 422 l s-1 km-2 o 15.00 hod.). Maximálny meraný špecifický odtok z povodia Lesný 263,7 l s-1 km-2 bol zaznamenaný 29. marca 2006 (vrchol 523 l s-1 km-2 o 12.00 hod.). V druhej časti príspevku je analyzovaný dlhodobý vývoj vodnej hodnoty snehu (SWE) v povodí Rybárik a Lesný, modelovanej zrážko-odtokovým modelom HBV-light. Po kalibrácii a verifikácii modelu boli modelom vypočítané denné vodné hodnoty snehu za 42-ročné obdobie 1965/66–2005/06. Z výsledkov vyplýva, že po dočasnom poklese maxím vodnej hodnoty snehu SWE v deväťdesiatych rokoch minulého storočia od roku 2002 došlo k opätovnému zvýšeniu vodnej hodnoty snehu. V zimnej sezóne 2005/06 bola vypočítaná najvyššia hodnota SWE od začiatku pozorovaní v oboch mikropovodiach.