J. Hydrol. Hydromech., Vol. 64, No. 4, 2016, p. 301 - 303, doi: 10.1515/johh-2016-0043
Information, English

Günter Blöschl, Jan Szolgay, Juraj Parajka, Silvia Kohnová, Pavol Miklánek: Thematic Issue on Floods in the Danube basin – processes, patterns, predictions

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• Data not available
  
  KEY WORDS: Data not available
  
  Address:
  - Günter Blöschl, Institute for Hydraulic and Water Resources Engineering, Vienna University of Technology, Karlsplatz 13/222, A-1040 Vienna, Austria.
  - Jan Szolgay, Slovak University of Technology in Bratislava, Faculty of Civil Engineering, Department of Land and Water Resources Management, Radlinského 11, 810 05 Bratislava, Slovakia.
  - Juraj Parajka, Institute for Hydraulic and Water Resources Engineering, Vienna University of Technology, Karlsplatz 13/222, A-1040 Vienna, Austria.
  - Silvia Kohnová, Slovak University of Technology in Bratislava, Faculty of Civil Engineering, Department of Land and Water Resources Management, Radlinského 11, 810 05 Bratislava, Slovakia.
  - Pavol Miklánek, Institute of Hydrology, Slovak Academy of Sciences, Dúbravská cesta 9, 841 04 Bratislava, Slovakia.

J. Hydrol. Hydromech., Vol. 64, No. 4, 2016, p. 304 - 315, doi: 10.1515/johh-2016-0041
Scientific Paper, English

Kamila Hlavčová, Silvia Kohnová, Marco Borga, Oliver Horvát, Pavel Šťastný, Pavla Pekárová, Oľga Majerčáková, Zuzana Danáčová: Post-event analysis and flash flood hydrology in Slovakia

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• This work examines the main features of the flash flood regime in Central Europe as revealed by an analysis of flash floods that have occurred in Slovakia. The work is organized into the following two parts: The first part focuses on estimating the rainfall-runoff relationships for 3 major flash flood events, which were among the most severe events since 1998 and caused a loss of lives and a large amount of damage. The selected flash floods occurred on the 20th of July, 1998, in the Malá Svinka and Dubovický Creek basins; the 24th of July, 2001, at Štrbský Creek; and the 19th of June, 2004, at Turniansky Creek. The analysis aims to assess the flash flood peaks and rainfall-runoff properties by combining post-flood surveys and the application of hydrological and hydraulic post-event analyses. Next, a spatially-distributed hydrological model based on the availability of the raster information of the landscape’s topography, soil and vegetation properties, and rainfall data was used to simulate the runoff. The results from the application of the distributed hydrological model were used to analyse the consistency of the surveyed peak discharges with respect to the estimated rainfall properties and drainage basins. In the second part these data were combined with observations from flash flood events which were observed during the last 100 years and are focused on an analysis of the relationship between the flood peaks and the catchment area. The envelope curve was shown to exhibit a more pronounced decrease with the catchment size with respect to other flash flood relationships found in the Mediterranean region. The differences between the two relationships mainly reflect changes in the coverage of the storm sizes and hydrological characteristics between the two regions.
  
  KEY WORDS: Flash flood; Slovakia; Post-event analysis; Hydrological modelling.
  
  Address:
  - Kamila Hlavčová, Slovak University of Technology in Bratislava, Faculty of Civil Engineering, Radlinského 11, 810 05 Bratislava, Slovakia. (Corresponding author. Tel.: Fax.: Email: kamila.hlavcova@stuba.sk)
  - Silvia Kohnová, Slovak University of Technology in Bratislava, Faculty of Civil Engineering, Radlinského 11, 810 05 Bratislava, Slovakia.
  - Marco Borga, Dept. of Land, the Environment, Agriculture and Forests, University of Padova, Via dell'Universita 16, 35020 Legnaro (PD), Italy.
  - Oliver Horvát, Comenius University in Bratislava, Faculty of Natural Sciences, Ilkovičova 6, 842 15 Bratislava, Slovakia.
  - Pavel Šťastný, Slovak Hydrometeorological Institute, Jeséniova 17, 833 15 Bratislava, Slovakia.
  - Pavla Pekárová, Institute of Hydrology of the Slovak Academy of Sciences, Dúbravská 9, 841 04 Bratislava, Slovakia.
  - Oľga Majerčáková, Slovak Hydrometeorological Institute, Jeséniova 17, 833 15 Bratislava, Slovakia.
  - Zuzana Danáčová, Slovak Hydrometeorological Institute, Jeséniova 17, 833 15 Bratislava, Slovakia.

J. Hydrol. Hydromech., Vol. 64, No. 4, 2016, p. 316 - 328, doi: 10.1515/johh-2016-0038
Scientific Paper, English

Pavel Krajčí, Michal Danko, Jozef Hlavčo, Zdeněk Kostka, Ladislav Holko: Experimental measurements for improved understanding and simulation of snowmelt events in the Western Tatra Mountains

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• Snow accumulation and melt are highly variable. Therefore, correct modeling of spatial variability of the snowmelt, timing and magnitude of catchment runoff still represents a challenge in mountain catchments for flood forecasting. The article presents the setup and results of detailed field measurements of snow related characteristics in a mountain microcatchment (area 59 000 m2, mean altitude 1509 m a. s. l.) in the Western Tatra Mountains, Slovakia obtained in winter 2015. Snow water equivalent (SWE) measurements at 27 points documented a very large spatial variability through the entire winter. For instance, range of the SWE values exceeded 500 mm at the end of the accumulation period (March 2015). Simple snow lysimeters indicated that variability of snowmelt and discharge measured at the catchment outlet corresponded well with the rise of air temperature above 0°C. Temperature measurements at soil surface were used to identify the snow cover duration at particular points. Snow melt duration was related to spatial distribution of snow cover and spatial patterns of snow radiation. Obtained data together with standard climatic data (precipitation and air temperature) were used to calibrate and validate the spatially distributed hydrological model MIKE-SHE. The spatial redistribution of input precipitation seems to be important for modeling even on such a small scale. Acceptable simulation of snow water equivalents and snow duration does not guarantee correct simulation of peakflow at shorttime (hourly) scale required for example in flood forecasting. Temporal variability of the stream discharge during the snowmelt period was simulated correctly, but the simulated discharge was overestimated.
  
  KEY WORDS: Snow accumulation and melt; Snowmelt rate; Snowmelt duration; Mountains; Snow lysimeter; MIKE-SHE.
  
  Address:
  - Pavel Krajčí, Institute of Hydrology, Slovak Academy of Sciences, Ondrašovská 17, Liptovský Mikuláš, Slovakia. (Corresponding author. Tel.: Fax.: Email: krajci@uh.savba.sk)
  - Michal Danko, Institute of Hydrology, Slovak Academy of Sciences, Ondrašovská 17, Liptovský Mikuláš, Slovakia.
  - Jozef Hlavčo, Institute of Hydrology, Slovak Academy of Sciences, Ondrašovská 17, Liptovský Mikuláš, Slovakia.
  - Zdeněk Kostka, Institute of Hydrology, Slovak Academy of Sciences, Ondrašovská 17, Liptovský Mikuláš, Slovakia.
  - Ladislav Holko, Institute of Hydrology, Slovak Academy of Sciences, Ondrašovská 17, Liptovský Mikuláš, Slovakia.

J. Hydrol. Hydromech., Vol. 64, No. 4, 2016, p. 329 - 336, doi: 10.1515/johh-2016-0040
Scientific Paper, English

Vasile Craciunescu, Gheorghe Stancalie, Anisoara Irimescu, Simona Catana, Denis Mihailescu, Argentina Nertan, George Morcov, Stefan Constantinescu: MODIS-based multi-parametric platform for mapping of flood affected areas. Case study: 2006 Danube extreme flood in Romania

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• Flooding remains the most widely distributed natural hazard in Europe, leading to significant economic and social impact. Earth observation data is presently capable of making fundamental contributions towards reducing the detrimental effects of extreme floods. Technological advance makes development of online services able to process high volumes of satellite data without the need of dedicated desktop software licenses possible. The main objective of the case study is to present and evaluate a methodology for mapping of flooded areas based on MODIS satellite images derived indices and using state-of-the-art geospatial web services. The methodology and the developed platform were tested with data for the historical flood event that affected the Danube floodplain in 2006 in Romania. The results proved that, despite the relative coarse resolution, MODIS data is very useful for mapping the development flooded area in large plain floods. Moreover it was shown, that the possibility to adapt and combine the existing global algorithms for flood detection to fit the local conditions is extremely important to obtain accurate results.
  
  KEY WORDS: Flood extent mapping; MODIS; Web services; 2006 Danube Flood.
  
  Address:
  - Vasile Craciunescu, National Meteorological Administration 97, Soseaua Bucuresti-Ploiesti, sector 1 013686, Bucharest, Romania. (Corresponding author. Tel.:+40-21-316 60 98 Fax.: +40-21-316 60 98 Email: vasile.craciunescu@meteoromania.ro)
  - Gheorghe Stancalie, National Meteorological Administration 97, Soseaua Bucuresti-Ploiesti, sector 1 013686, Bucharest, Romania.
  - Anisoara Irimescu, National Meteorological Administration 97, Soseaua Bucuresti-Ploiesti, sector 1 013686, Bucharest, Romania.
  - Simona Catana, National Meteorological Administration 97, Soseaua Bucuresti-Ploiesti, sector 1 013686, Bucharest, Romania.
  - Denis Mihailescu, National Meteorological Administration 97, Soseaua Bucuresti-Ploiesti, sector 1 013686, Bucharest, Romania.
  - Argentina Nertan, National Meteorological Administration 97, Soseaua Bucuresti-Ploiesti, sector 1 013686, Bucharest, Romania.
  - George Morcov, National Meteorological Administration 97, Soseaua Bucuresti-Ploiesti, sector 1 013686, Bucharest, Romania.
  - Stefan Constantinescu, Faculty of Geography, University of Bucharest 1, Bd. Nicolae Bălcescu, Sector 1, Bucharest, Romania.

J. Hydrol. Hydromech., Vol. 64, No. 4, 2016, p. 337 - 348, doi: 10.1515/johh-2016-0050
Scientific Paper, English

Veronika Bačová Mitková, Pavla Pekárová, Pavol Miklánek, Ján Pekár: Hydrological simulation of flood transformations in the upper Danube River: Case study of large flood events

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• The problem of understand natural processes as factors that restrict, limit or even jeopardize the interests of human society is currently of great concern. The natural transformation of flood waves is increasingly affected and disturbed by artificial interventions in river basins. The Danube River basin is an area of high economic and water management importance. Channel training can result in changes in the transformation of flood waves and different hydrographic shapes of flood waves compared with the past. The estimation and evolution of the transformation of historical flood waves under recent river conditions is only possible by model simulations. For this purpose a nonlinear reservoir cascade model was constructed. The NLN-Danube nonlinear reservoir river model was used to simulate the transformation of flood waves in four sections of the Danube River from Kienstock (Austria) to Štúrovo (Slovakia) under relatively recent river reach conditions. The model was individually calibrated for two extreme events in August 2002 and June 2013. Some floods that occurred on the Danube during the period of 1991–2002 were used for the validation of the model. The model was used to identify changes in the transformational properties of the Danube channel in the selected river reach for some historical summer floods (1899, 1954 1965 and 1975). Finally, a simulation of flood wave propagation of the most destructive Danube flood of the last millennium (August 1501) is discussed.
  
  KEY WORDS: Danube River; June 2013 flood; Hydrological nonlinear river routing model; Catastrophic flood scenario.
  
  Address:
  - Veronika Bačová Mitková, Institute of Hydrology Slovak Academy of the Sciences, Dúbravská cesta 9, 841 04 Bratislava, Slovakia. (Corresponding author. Tel.: Fax.: Email: mitkova@uh.savba.sk)
  - Pavla Pekárová, Institute of Hydrology Slovak Academy of the Sciences, Dúbravská cesta 9, 841 04 Bratislava, Slovakia.
  - Pavol Miklánek, Institute of Hydrology Slovak Academy of the Sciences, Dúbravská cesta 9, 841 04 Bratislava, Slovakia.
  - Ján Pekár, Comenius University, Faculty of Mathematics, Physics and Informatics, Mlynská dolina F1, 842 48 Bratislava, Slovakia.

J. Hydrol. Hydromech., Vol. 64, No. 4, 2016, p. 349 - 356, doi: 10.1515/johh-2016-0035
Scientific Paper, English

Daniel Skublics, Günter Blöschl, Peter Rutschmann: Effect of river training on flood retention of the Bavarian Danube

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• The Bavarian Danube River has experienced numerous large flood events in recent years which make flood management an urgent matter. The propagation of flood waves along the river is heavily influenced by controlled and natural flood retention. Over the past centuries, natural flood retention areas were lost due to river training, and the hydraulic characteristics of the channel-flood plain system were modified. The purpose of this paper is to understand the effect of river training on the flood retention characteristics along the Bavarian Danube. Systematic two-dimensional hydrodynamic modelling shows that extreme floods are attenuated more strongly in the present state of the channel-flood plain system than they were historically. This is because the retention areas are filled later during the event, so the attenuation effect is much larger for the same magnitude of the retention volume. Natural flood retention is therefore not an effective management option for reducing extreme floods on the Bavarian Danube. Controlled flood retention measures provide a higher efficiency regarding peak attenuation to retention volume ratio. On the other hand, the delay of flood peaks due to natural retention may be beneficial for the superposition of the flood waves with contributions from downstream tributaries.
  
  KEY WORDS: Flood retention; Flood plain; Inundation areas; Flood management; Hydrodynamic modelling.
  
  Address:
  - Daniel Skublics, Wasserwirtschaftsamt Rosenheim, Königstraße 19, 83022 Rosenheim, Germany. (Corresponding author. Tel.: Fax.: Email: daniel.skublics@wwa-ro.bayern.de)
  - Günter Blöschl, Institute of Hydraulic Engineering and Water Resources Management, Vienna University of Technology, Karlsplatz 13/222, A-1040 Vienna, Austria.
  - Peter Rutschmann, Chair of Hydraulic Engineering and Water Resources Management, Technische Universität München, Arcisstraße 21, 80333 Munich, Germany.

J. Hydrol. Hydromech., Vol. 64, No. 4, 2016, p. 357 - 366, doi: 10.1515/johh-2016-0037
Scientific Paper, English

Katarína Jeneiová, Silvia Kohnová, Julia Hall, Juraj Parajka: Variability of seasonal floods in the Upper Danube River basin

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• The objective of this study is to analyse the spatial variability of seasonal flood occurrences in the Upper Danube region for the period 1961-2010. The analysis focuses on the understanding of the factors that control the spatial variability of winter and summer floods in 88 basins with different physiographic conditions. The evaluation is based on circular statistics, which compare the changes in the mean date and in the seasonal flood concentration index within a year or predefined season. The results indicate that summer half-year and winter half-year floods are dominant in the Alps and northern Danube tributaries, respectively. A comparison of the relative magnitude of flood events indicates that summer half-year floods are on average more than 50% larger than floods in winter. The evaluation of flood occurrence showed that the values of seasonal flood concentration index (median 0.75) in comparison to the annual floods (median 0.58) shows higher temporal concentration of floods. The flood seasonality of winter events is dominant in the Alps; however, along the northern fringe (i.e. the Isar, Iller and Inn River) the timing of winter half-year floods is diverse. The seasonal concentration of summer floods tends to increase with increasing mean elevation of the basins. The occurrence of the three largest summer floods is more stable, i.e. they tend to occur around the same time for the majority of analysed basins. The results show that fixing the summer and winter seasons to specific months does not always allow a clear distinction of the main flood generation processes. Therefore, criteria to define flood typologies that are more robust are needed for regions such as the Upper Danube, with large climate and topographical variability between the lowland and high elevations, particularly for the assessment of the effect of increasing air temperature on snowmelt runoff and associated floods.
  
  KEY WORDS: Seasonality; Summer and winter floods; Upper Danube River basin; Comparative hydrology.
  
  Address:
  - Katarína Jeneiová, Slovak University of Technology in Bratislava, Faculty of Civil Engineering, Radlinského 11, 810 05 Bratislava, Slovakia.
  - Silvia Kohnová, Slovak University of Technology in Bratislava, Faculty of Civil Engineering, Radlinského 11, 810 05 Bratislava, Slovakia. (Corresponding author. Tel.:+421 (2) 59 274 623 Fax.: Email: silvia.kohnova@stuba.sk)
  - Julia Hall, Institute of Hydraulic Engineering and Water Resources Management, Vienna University of Technology, Karlsplatz 13/222, A-1040, Vienna, Austria.
  - Juraj Parajka, Institute of Hydraulic Engineering and Water Resources Management, Vienna University of Technology, Karlsplatz 13/222, A-1040, Vienna, Austria.

J. Hydrol. Hydromech., Vol. 64, No. 4, 2016, p. 367 - 381, doi: 10.1515/johh-2016-0042
Scientific Paper, English

Ján Szolgay, Ladislav Gaál, Tomáš Bacigál, Silvia Kohnová, Kamila Hlavčová, Roman Výleta, Juraj Parajka, Günter Blöschl: A regional comparative analysis of empirical and theoretical flood peak-volume relationships

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• This paper analyses the bivariate relationship between flood peaks and corresponding flood event volumes modelled by empirical and theoretical copulas in a regional context, with a focus on flood generation processes in general, the regional differentiation of these and the effect of the sample size on reliable discrimination among models. A total of 72 catchments in North-West of Austria are analysed for the period 1976–2007. From the hourly runoff data set, 25 697 flood events were isolated and assigned to one of three flood process types: synoptic floods (including long- and short-rain floods), flash floods or snowmelt floods (both rain-on-snow and snowmelt floods). The first step of the analysis examines whether the empirical peak-volume copulas of different flood process types are regionally statistically distinguishable, separately for each catchment and the role of the sample size on the strength of the statements. The results indicate that the empirical copulas of flash floods tend to be different from those of the synoptic and snowmelt floods. The second step examines how similar are the empirical flood peak-volume copulas between catchments for a given flood type across the region. Empirical copulas of synoptic floods are the least similar between the catchments, however with the decrease of the sample size the difference between the performances of the process types becomes small. The third step examines the goodness-of-fit of different commonly used copula types to the data samples that represent the annual maxima of flood peaks and the respective volumes both regardless of flood generating processes (the traditional engineering approach) and also considering the three process-based classes. Extreme value copulas (Galambos, Gumbel and Hüsler-Reiss) show the best performance both for synoptic and flash floods, while the Frank copula shows the best performance for snowmelt floods. It is concluded that there is merit in treating flood types separately when analysing and estimating flood peak-volume dependence copulas; however, even the enlarged dataset gained by the process-based analysis in this study does not give sufficient information for a reliable model choice for multivariate statistical analysis of flood peaks and volumes.
  
  KEY WORDS: Flood types; Regionalisation; Flood peaks; Flood volumes; Copulas; Goodness-of-fit; Comparative hydrology.
  
  Address:
  - Ján Szolgay, Slovak University of Technology in Bratislava, Faculty of Civil Engineering, Department of Land and Water Resources Management, Radlinského 11, 810 05 Bratislava, Slovakia.
  - Ladislav Gaál, Slovak University of Technology in Bratislava, Faculty of Civil Engineering, Department of Land and Water Resources Management, Radlinského 11, 810 05 Bratislava, Slovakia. MicroStep-MIS, s.r.o., Čavojského 1, SK 841 04 Bratislava 4, Slovakia.
  - Tomáš Bacigál, Slovak University of Technology in Bratislava, Faculty of Civil Engineering, Department of Mathematics and Constructive Geometry, Radlinského 11, 810 05 Bratislava, Slovakia.
  - Silvia Kohnová, Slovak University of Technology in Bratislava, Faculty of Civil Engineering, Department of Land and Water Resources Management, Radlinského 11, 810 05 Bratislava, Slovakia. (Corresponding author. Tel.: Fax.: Email: silvia.kohnova@stuba.sk)
  - Kamila Hlavčová, Slovak University of Technology in Bratislava, Faculty of Civil Engineering, Department of Land and Water Resources Management, Radlinského 11, 810 05 Bratislava, Slovakia.
  - Roman Výleta, Slovak University of Technology in Bratislava, Faculty of Civil Engineering, Department of Land and Water Resources Management, Radlinského 11, 810 05 Bratislava, Slovakia.
  - Juraj Parajka, Institute for Hydraulic and Water Resources Engineering, Vienna University of Technology, Karlsplatz 13/223, A-1040 Vienna, Austria.
  - Günter Blöschl, Institute for Hydraulic and Water Resources Engineering, Vienna University of Technology, Karlsplatz 13/223, A-1040 Vienna, Austria.

J. Hydrol. Hydromech., Vol. 64, No. 4, 2016, p. 382 - 392, doi: 10.1515/johh-2016-0049
Scientific Paper, English

George Papaioannou, Silvia Kohnová, Tomáš Bacigál, Ján Szolgay, Kamila Hlavčová, Athanasios Loukas: Joint modelling of flood peaks and volumes: A copula application for the Danube River

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• Flood frequency analysis is usually performed as a univariate analysis of flood peaks using a suitable theoretical probability distribution of the annual maximum flood peaks or peak over threshold values. However, other flood attributes, such as flood volume and duration, are necessary for the design of hydrotechnical projects, too. In this study, the suitability of various copula families for a bivariate analysis of peak discharges and flood volumes has been tested. Streamflow data from selected gauging stations along the whole Danube River have been used. Kendall’s rank correlation coefficient (tau) quantifies the dependence between flood peak discharge and flood volume settings. The methodology is applied to two different data samples: 1) annual maximum flood (AMF) peaks combined with annual maximum flow volumes of fixed durations at 5, 10, 15, 20, 25, 30 and 60 days, respectively (which can be regarded as a regime analysis of the dependence between the extremes of both variables in a given year), and 2) annual maximum flood (AMF) peaks with corresponding flood volumes (which is a typical choice for engineering studies). The bivariate modelling of the extracted peak discharge - flood volume couples is achieved with the use of the Ali-Mikhail-Haq (AMH), Clayton, Frank, Joe, Gumbel, Hüsler-Reiss, Galambos, Tawn, Normal, Plackett and FGM copula families. Scatterplots of the observed and simulated peak discharge - flood volume pairs and goodness-of-fit tests have been used to assess the overall applicability of the copulas as well as observing any changes in suitable models along the Danube River. The results indicate that for the second data sampling method, almost all of the considered Archimedean class copula families perform better than the other copula families selected for this study, and that for the first method, only the upper-tail-flat copulas excel (except for the AMH copula due to its inability to model stronger relationships).
  
  KEY WORDS: Bivariate frequency analysis; Copulas; Dependence of flood peaks and volumes; Kendall’s rank correlation coefficient; Danube River.
  
  Address:
  - George Papaioannou, Laboratory of Hydrology and Aquatic Systems Analysis, Department of Civil Engineering, University of Thessally, Pedion Areos, 38334 Volos, Greece. (Corresponding author. Tel.:+302421074153 Fax.: Email: gpapaioa@uth.gr)
  - Silvia Kohnová, Slovak University of Technology in Bratislava, Faculty of Civil Engineering, Department of Land and Water Resources Management, Radlinského 11, 810 05 Bratislava, Slovakia.
  - Tomáš Bacigál, Slovak University of Technology in Bratislava, Faculty of Civil Engineering, Department of Mathematics and Constructive Geometry, Radlinského 11, 810 05 Bratislava, Slovakia.
  - Ján Szolgay, Slovak University of Technology in Bratislava, Faculty of Civil Engineering, Department of Land and Water Resources Management, Radlinského 11, 810 05 Bratislava, Slovakia.
  - Kamila Hlavčová, Slovak University of Technology in Bratislava, Faculty of Civil Engineering, Department of Land and Water Resources Management, Radlinského 11, 810 05 Bratislava, Slovakia.
  - Athanasios Loukas, Laboratory of Hydrology and Aquatic Systems Analysis, Department of Civil Engineering, University of Thessally, Pedion Areos, 38334 Volos, Greece.

J. Hydrol. Hydromech., Vol. 64, No. 4, 2016, p. 393 - 403, doi: 10.1515/johh-2016-0045
Scientific Paper, English

Pavla Pekárová, Branislav Pramuk, Dana Halmová, Pavol Miklánek, Stevan Prohaska, Ján Pekár: Identification of long-term high-flow regime changes in selected stations along the Danube River

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• 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.
  
  KEY WORDS: Floods; Hydrological regime; Long streamflow series; Danube River; Flow thresholds; Flood trends.
  
  Address:
  - Pavla Pekárová, Institute of Hydrology, Slovak Academy of Sciences, Dúbravská cesta 9, 841 04 Bratislava, Slovakia.
  - Branislav Pramuk, Institute of Hydrology, Slovak Academy of Sciences, Dúbravská cesta 9, 841 04 Bratislava, Slovakia.
  - Dana Halmová, Institute of Hydrology, Slovak Academy of Sciences, Dúbravská cesta 9, 841 04 Bratislava, Slovakia. (Corresponding author. Tel.:+4212 44259404 Fax.: +4212 44259404 Email: halmova@uh.savba.sk)
  - Pavol Miklánek, Institute of Hydrology, Slovak Academy of Sciences, Dúbravská cesta 9, 841 04 Bratislava, Slovakia.
  - Stevan Prohaska, Jaroslav Černi Institute for the Development of Water Resources, Jaroslava Černog 80, 11226 Belgrade, Serbia.
  - Ján Pekár, Comenius University in Bratislava, Faculty of Mathematics, Physics, and Informatics, Mlynská dolina F1, 842 48 Bratislava, Slovakia.

J. Hydrol. Hydromech., Vol. 64, No. 4, 2016, p. 404 - 414, doi: 10.1515/johh-2016-0033
Scientific Paper, English

Thomas Nester, Jürgen Komma, Günter Blöschl: Real time flood forecasting in the Upper Danube basin

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• This paper reports on experience with developing the flood forecasting model for the Upper Danube basin and its operational use since 2006. The model system consists of hydrological and hydrodynamic components, and involves precipitation forecasts. The model parameters were estimated based on the dominant processes concept. Runoff data are assimilated in real time to update modelled soil moisture. An analysis of the model performance indicates 88% of the snow cover in the basin to be modelled correctly on more than 80% of the days. Runoff forecasting errors decrease with catchment area and increase with forecast lead time. The forecast ensemble spread is shown to be a meaningful indicator of the forecast uncertainty. During the 2013 flood, there was a tendency for the precipitation forecasts to underestimate event precipitation and for the runoff model to overestimate runoff generation which resulted in, overall, rather accurate runoff forecasts. It is suggested that the human forecaster plays an essential role in interpreting the model results and, if needed, adjusting them before issuing the forecasts to the general public.
  
  KEY WORDS: Hydrological model; Real time forecasting; Dominant processes; Data assimilation.
  
  Address:
  - Thomas Nester, Institute of Hydraulic Engineering and Water Resources Management, Vienna University of Technology, Karlsplatz 13/222, A-1040, Vienna, Austria. (Corresponding author. Tel.: Fax.: Email: nester@hydro.tuwien.ac.at)
  - Jürgen Komma, Institute of Hydraulic Engineering and Water Resources Management, Vienna University of Technology, Karlsplatz 13/222, A-1040, Vienna, Austria.
  - Günter Blöschl, Institute of Hydraulic Engineering and Water Resources Management, Vienna University of Technology, Karlsplatz 13/222, A-1040, Vienna, Austria.

J. Hydrol. Hydromech., Vol. 64, No. 4, 2016, p. 415 - 425, doi: 10.1515/johh-2016-0036
Scientific Paper, English

Vojtěch Svoboda, Martin Hanel, Petr Máca, Jan Kyselý: Projected changes of rainfall event characteristics for the Czech Republic

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• Projected changes of warm season (May–September) rainfall events in an ensemble of 30 regional climate model (RCM) simulations are assessed for the Czech Republic. Individual rainfall events are identified using the concept of minimum inter-event time and only heavy events are considered. The changes of rainfall event characteristics are evaluated between the control (1981–2000) and two scenario (2020–2049 and 2070–2099) periods. Despite a consistent decrease in the number of heavy rainfall events, there is a large uncertainty in projected changes in seasonal precipitation total due to heavy events. Most considered characteristics (rainfall event depth, mean rainfall rate, maximum 60-min rainfall intensity and indicators of rainfall event erosivity) are projected to increase and larger increases appear for more extreme values. Only rainfall event duration slightly decreases in the more distant scenario period according to the RCM simulations. As a consequence, the number of less extreme heavy rainfall events as well as the number of long events decreases in majority of the RCM simulations. Changes in most event characteristics (and especially in characteristics related to the rainfall intensity) depend on changes in radiative forcing and temperature for the future periods. Only changes in the number of events and seasonal total due to heavy events depend significantly on altitude.
  
  KEY WORDS: Rainfall event; Hourly rainfall; Regional climate model; Climate change.
  
  Address:
  - Vojtěch Svoboda, Faculty of Environmental Sciences, Czech University of Life Sciences Prague, Kamýcká 129, 165 21 Prague 6–Suchdol, Czech Republic.
  - Martin Hanel, Faculty of Environmental Sciences, Czech University of Life Sciences Prague, Kamýcká 129, 165 21 Prague 6–Suchdol, Czech Republic. Technical University of Liberec, Studentská 1402/2, 461 17 Liberec 1, Czech Republic. (Corresponding author. Tel.:+420 22438 3834 Fax.: Email: hanel@fzp.czu.cz)
  - Petr Máca, Faculty of Environmental Sciences, Czech University of Life Sciences Prague, Kamýcká 129, 165 21 Prague 6–Suchdol, Czech Republic.
  - Jan Kyselý, Faculty of Environmental Sciences, Czech University of Life Sciences Prague, Kamýcká 129, 165 21 Prague 6–Suchdol, Czech Republic. Institute of Atmospheric Physics, Czech Academy of Sciences, Boční II 1401, 141 31 Prague 4–Spořilov, Czech Republic.

J. Hydrol. Hydromech., Vol. 64, No. 4, 2016, p. 426 - 437, doi: 10.1515/johh-2016-0032
Scientific Paper, English

Mojca Šraj, Alberto Viglione, Juraj Parajka, Günter Blöschl: The influence of non-stationarity in extreme hydrological events on flood frequency estimation

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• Substantial evidence shows that the frequency of hydrological extremes has been changing and is likely to continue to change in the near future. Non-stationary models for flood frequency analyses are one method of accounting for these changes in estimating design values. The objective of the present study is to compare four models in terms of goodness of fit, their uncertainties, the parameter estimation methods and the implications for estimating flood quantiles. Stationary and non-stationary models using the GEV distribution were considered, with parameters dependent on time and on annual precipitation. Furthermore, in order to study the influence of the parameter estimation approach on the results, the maximum likelihood (MLE) and Bayesian Monte Carlo Markov chain (MCMC) methods were compared. The methods were tested for two gauging stations in Slovenia that exhibit significantly increasing trends in annual maximum (AM) discharge series. The comparison of the models suggests that the stationary model tends to underestimate flood quantiles relative to the non-stationary models in recent years. The model with annual precipitation as a covariate exhibits the best goodness-of-fit performance. For a 10% increase in annual precipitation, the 10-year flood increases by 8%. Use of the model for design purposes requires scenarios of future annual precipitation. It is argued that these may be obtained more reliably than scenarios of extreme event precipitation which makes the proposed model more practically useful than alternative models.
  
  KEY WORDS: Nonstationarity; Trends; Flood frequency analysis; Return period; Design discharge; Climate variability.
  
  Address:
  - Mojca Šraj, University of Ljubljana, Faculty of Civil and Geodetic Engineering, Jamova 2, SI-1000 Ljubljana, Slovenia.
  - Alberto Viglione, Vienna University of Technology, Institute of Hydraulic Engineering and Water Resources Management, Karlsplatz 13/222, A-1040 Vienna, Austria.
  - Juraj Parajka, Vienna University of Technology, Institute of Hydraulic Engineering and Water Resources Management, Karlsplatz 13/222, A-1040 Vienna, Austria.
  - Günter Blöschl, Vienna University of Technology, Institute of Hydraulic Engineering and Water Resources Management, Karlsplatz 13/222, A-1040 Vienna, Austria. (Corresponding author. Tel.:+43-1-58801-22315 Fax.: +43-1-58801-22399 Email: bloeschl@hydro.tuwien.ac.at)

J. Hydrol. Hydromech., Vol. 64, No. 4, 2016, p. 438 - 447, doi: 10.1515/johh-2016-0034
Scientific Paper, English

Claire Brenner, Claude Meisch, Benjamin Apperl, Karsten Schulz: Towards periodic and time-referenced flood risk assessment using airborne remote sensing

 Full Text in PDF     57 DOWNLOADS

• Flood risk management is founded on the regular assessment of damage potential. A significant parameter for assessing damage potential is the number of at-risk objects. However, data sets on exposure are often incomplete and/or lack time-references. Airborne remote sensing data, such as orthophotos, offers a regularly-updated, time-referenced depiction of land use. As such, remote sensing data compensates for incomplete data sources (such as digital cadastral maps). Orthophotos can even be used to analyze the temporal dynamics of flood damage potential, providing that timereferenced information is available for multiple time points. This paper describes a method for integrating orthophotos into flood risk analyses. In Austria, orthophotos are updated every three years, allowing their integration into cyclical flood risk assessments. The results of a case study presented in this paper demonstrate that orthophotos are most useful where other data sources, such as digital cadastral maps, are incomplete. In such situations, orthophotos lead to a significant increase in estimated damage potential. Orthophoto analysis allows damage potentials to be re-assessed at regular intervals, another major advantage over digital cadastral maps. Orthophoto analysis thus supports the evaluation of flood risk management options.
  
  KEY WORDS: Flood risk management; Damage potential analysis; Object-based image analysis; Orthophoto analysis; Building detection.
  
  Address:
  - Claire Brenner, University of Natural Resources and Life Sciences, Vienna, Institute of Water Management, Hydrology and Hydraulic Engineering (IWHW), Muthgasse 18, 1190 Vienna, Austria. (Corresponding author. Tel.: Fax.: Email: claire.brenner@boku.ac.at)
  - Claude Meisch, University of Natural Resources and Life Sciences, Vienna, Institute of Water Management, Hydrology and Hydraulic Engineering (IWHW), Muthgasse 18, 1190 Vienna, Austria.
  - Benjamin Apperl, University of Natural Resources and Life Sciences, Vienna, Institute of Water Management, Hydrology and Hydraulic Engineering (IWHW), Muthgasse 18, 1190 Vienna, Austria.
  - Karsten Schulz, University of Natural Resources and Life Sciences, Vienna, Institute of Water Management, Hydrology and Hydraulic Engineering (IWHW), Muthgasse 18, 1190 Vienna, Austria.