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Pekarova P.,Slovak Academy of Sciences | Halmova D.,Slovak Academy of Sciences | Mitkova V.B.,Slovak Academy of Sciences | Miklanek P.,Slovak Academy of Sciences | And 2 more authors.
Journal of Hydrology and Hydromechanics | Year: 2013

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. Source

Skvareninova J.,Technical University In Zvolen | Snopkova Z.,Slovak Hydrometeorological Institute
Folia Oecologica | Year: 2010

The paper informs about the evaluation of observed selected vegetative (bud burst beginning, the first May sprouts occurrence) and generative (the lasting male flowers and the general flowering) phenological stages of Norway spruce (Picea abies (L.) Karst.). There were analysed data from 38 phenological stations in Slovakia within the period 1996-2008. The stations were situated in the range from 100 m to 940 m a.s.l. and divided into 3 altitudinal groups. The mean onset date of the bud burst stage was from the 21st of April till the 6th of May, the first May sprouts occurred from the 2nd till the 18th of May. Male flowers were lasting from the 12th till the 19th of May, the general flowering lasted from the 17 th till the 24th May on average. The shifts of observed vegetative phenological stages among particular altitudinal groups represented 7-9 days, and they kept their temporal succession. Generative phenological stages began with the differences among p1articular altitudinal groups approaching 2-5 days regardless the altitude itself. At lower situated stations, up to 500 m a.s.l., the vegetative phenological stages were observed shifted positively by 3.3-8.5 days, above 500 m a.s.l. these stages were delayed by 0.8-2.8 days. The generative phenological stages manifested a decreasing trend with a shift by 3.6-11.2 days sooner. The phenological phases shortens are shorter with increasing altitude. Source

Holko L.,Slovak Academy of Sciences | Parajka J.,Slovak Academy of Sciences | Parajka J.,Vienna University of Technology | Kostka Z.,Slovak Academy of Sciences | And 2 more authors.
Journal of Hydrology | Year: 2011

This article evaluates the spatial and temporal changes in streamflow flashiness in 122 mountain catchments in Slovakia and Austria. The flashiness is quantified by the Richards-Baker flashiness index (FI), which is the ratio of absolute day-to-day fluctuations of streamflow relative to total flow in a year. The analysis is based on daily streamflow data from the period 1976 to 2005. The results show that the average day-to-day fluctuations of streamflow vary from 6% to 43%, depending on the catchment. The spatial pattern of the FI reflects the variations in the main geological units and generally shows a trend of decreasing flashiness with increasing size of the catchment. Statistically significant temporal trends in flashiness are found in 7 Slovak and 22 Austrian catchments. Most of these trends are related to anthropogenic effects, while, in a few catchments, the change in annual flashiness appears to be caused by changes in precipitation seasonality. A multivariate statistical analysis of FI indicates negative correlations with catchment area, mean catchment elevation, percents of forest cover, agricultural land and Quaternary geology. Positive correlations are found between FI and Tertiary and Calcareous geologies. Extrapolating the regression models beyond the observed range of catchment attributes used in the estimation leads to significant prediction errors. In order to better interpret the FI values, a statistically significant relationship was found between the FI and the frequency of peak flows exceeding the long-term mean as well as between the FI and the 5% quantile of daily streamflow. © 2011 Elsevier B.V. Source

Prokesova R.,Matej Bel University | Medvedova A.,Matej Bel University | Taborik P.,University of Ostrava | Snopkova Z.,Slovak Hydrometeorological Institute
Landslides | Year: 2013

It is a widely accepted idea that hydrologically triggered deep-seated landslides are initiated by an increase in pore-water pressure on potential slip surface induced by rising groundwater level after prolonged period of intense rainfall although the process is not fully understood. In order to contribute to better understanding, the rainfall-groundwater relationships, hydrogeological monitoring and repeated geoelectrical imaging were carried out from March 2007 to April 2011 in large deep-seated landslide near Ľubietová (Western Carpathians) catastrophically reactivated at the end of February 1977. Based on our observations, groundwater level (GWL) response to precipitation differs considerably with respect to both overall hydrological conditions and GWL mean depth. While the rate of GWL increase up to 25 cm/day were measured after some rainfall events during wet periods, noticeably lower recharge rate (up to 1-2 cm/day) and delayed GWL response to rainfall (usually from 2 weeks to 2-4 months) were observed at the beginning of the wet season after considerable depression of GWLs due to previous effective rainfall deficit. Likewise, slow GWL fluctuations without short-term oscillations are typical for deeper GWLs. Thus, long-term (several seasons to several years) hydrological conditions affect markedly groundwater response to rainfall events in the studied landslide and can be crucial for its behaviour. Comparison of hydrological conditions characterising the analysed period with those that accompanied the landslide reactivation in 1977 allow us to assume that slightly above-average rainy season following the prolonged wet period can be far more responsible for movement acceleration (and possibly failure initiation) in deep landslides than the isolated season of extreme precipitation following a longer dry period. This is true especially for landslides in regions with significant seasonal temperature changes where potential effective precipitation (PEP), calculated as excess of precipitation (P) over potential evapotranspiration (PET), may be efficiently used for estimation of slope saturation condition. © 2012 Springer-Verlag. Source

Bedka K.M.,NASA | Wang C.,Science Systems And Applications Inc. | Rogers R.,University of Alabama in Huntsville | Carey L.D.,University of Alabama in Huntsville | And 2 more authors.
Weather and Forecasting | Year: 2015

The Geostationary Operational Environmental Satellite-14 (GOES-14) Imager operated in 1-min Super Rapid Scan Operations for GOES-R (SRSOR) mode during summer and fall of 2012 to emulate the high temporal resolution sampling of the GOES-R Advanced Baseline Imager (ABI). The current GOES operational scan interval is 15-30 min, which is too coarse to capture details important for severe convective storm forecasting including 1) when indicators of a severe storm such as rapid cloud-top cooling, overshooting tops, and above-anvil cirrus plumes first appear; 2) how satellite-observed cloud tops truly evolve over time; and 3) how satellite cloud-top observations compare with radar and lightning observations at high temporal resolution. In this paper, SRSOR data, radar, and lightning observations are used to analyze five convective storms, four of which were severe, to address these uncertainties. GOES cloud-top cooling, increased lightning flash rates, and peak precipitation echo tops often preceded severe weather, signaling rapid intensification of the storm updraft. Near the time of several severe hail or damaging wind events, GOES cloud-top temperatures and radar echo tops were warming rapidly, which indicated variability in the storm updraft that could have allowed the hail and wind gusts to reach the surface. Above-anvil cirrus plumes were another prominent indicator of impending severe weather. Detailed analysis of storms throughout the 2012 SRSOR period indicates that 57% of the plume-producing storms were severe and 85% of plumes from severe storms appeared before a severe weather report with an average lead time of 18 min, 9 min earlier than what would be observed by GOES operational scanning. © 2015 American Meteorological Society. Source

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