A methodology for the estimation of control flood wave hydrographs for the Horné Orešany reservoir

Abstract

Recent changes in climatic characteristics and consequent changes in the discharges and in the hydrological response of watersheds raise questions about the safety of water structures. Changes in flood wave characteristics (shape, volume, peak flow) may significantly affect the functionality of these structures. The study proposes a methodology for constructing design wave and flood hydrographs using discharge time series. A case study was carried out in the Little Carpathians watershed of the Parná River, above the profile of the Horné Orešany reservoir in Slovakia. The volumes and characteristic shapes of the flood waves with the maximum annual and seasonal discharges were determined using the Floodsep software. Subsequently, the T-year annual and seasonal discharges were estimated. Then, for pairs of the Tyear discharges and the associated volumes of flood waves, a joint probability distribution was constructed by copula functions. The associated volume of the T-year peak discharges was selected from the copula, and the probability of exceeding it was determined. Based on this analysis, a set of annual and seasonal control flood waves with the design maximum discharge, the associated volume with the selected probability, and the typical shape of the flood wave was constructed. This research provides satisfactory results for designing control waves necessary for assessing water structures with extreme loads and establishing a functional methodology for assessing other water structures in the region.

The testing of a multivariate probabilistic framework for reservoir safety evaluation and flood risks assessment in Slovakia: A study on the Parná and Belá Rivers

“…The maximum summer discharges are from June to October; the maximum winter discharges are from November to May. The flood hydrograph characteristics of the seasonal maximum and annual maximum series of the flood peaks (Qmax), flood durations (D) and flood volumes (V) were separated using a semi-automatic procedure that identifies the beginning and end of flood events, as characterized by the position of their peaks (see details in Liová et al (2022)). The method then separates the baseflow using one of the pre-defined and frequently used approaches and, using a set of rules, tries to estimate the positions of the beginning and end of a given event.…”

“…The shape of the design synthetic flood hydrographs was derived from the fragments of the observed flood events in the dataset (the hydrographs were centered on the peak position), which have been simplified to maintain the monotonicity of their rising and falling limbs (unimodal to multimodal hydrographs). When design synthetic flood hydrographs are constructed, the important parameter is the percentile, which affects the shape of the representative hydrograph (see Liová et al, 2022). The task of this study was not to deal with the shape of the flood hydrographs, which would allow a designer to choose the appropriate critical shape of the flood design for the given purpose.…”

An assessment of the uncertainty of the extremity of flood waves with vine copulas

“…The gauging station is situated above the reservoir on the Parná River at rkm 26.8 and has a basin area of 37.86 km 2 . A more detailed description of the basin can be found in Liová et al (2022). The discharge time series in hourly time steps and the maximum annual discharges used in the analysis were provided by the Slovak Hydrometeorological Institute (SHMI) for the period from 01.11.1988 to 31.12.2021.…”

“…The sources of the uncertainty are rooted in the length and quality of the hydrological records, the selection of uni-and multivariate statistical models, and the estimation of the parameters. To guarantee reliable flood wave estimates for designs, such uncertainties must be quantified and communicated to practitioners (Brunner et al, 2018;Liová et al, 2022). Traditional uncertainty analyses of univariate design variables in hydrology are well established; they focus on many relevant aspects of the problem, such as the choice of the probability distributions, their parameter uncertainties, and comparisons of annual maxima sampling versus peak-over-threshold sampling (Beven and Hall, 2014;Kjeldsen et al, 2014).…”

Characteristics of runoff events in the Upper Váh River catchment in the warm period of year

“…The existing studies were mostly devoted to the Danube and Morava rivers (e.g. Pekárová et al, 2004;Danáčová and Szolgay, 2005;Szolgay et al, 2006). Contributions of the subcatchments to discharge evolution in a river network can vary during specific conditions.…”