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Natural Hazards and Earth System Sciences An interactive open-access journal of the European Geosciences Union
© Author(s) 2013. This work is distributed under
the Creative Commons Attribution 3.0 License.
Research article
31 Oct 2013
Review status
This discussion paper is a preprint. It has been under review for the journal Natural Hazards and Earth System Sciences (NHESS). The manuscript was not accepted for further review after discussion.
Application of a hybrid approach in nonstationary flood frequency analysis – a Polish perspective
K. Kochanek1, W. G. Strupczewski1, E. Bogdanowicz2, W. Feluch3, and I. Markiewicz1 1Institute of Geophysics, Polish Academy of Sciences, Księcia Janusza 64, 01-452 Warsaw, Poland
2Institute of Meteorology and Water Management, Podleśna 61, 01-673 Warsaw, Poland
3Warsaw University of Technology, Łukasiewicza 17, 09-400 Płock, Poland
Abstract. The alleged changes in rivers' flow regime resulted in the surge in the methods of non-stationary flood frequency analysis (NFFA). The maximum likelihood method is said to produce big systematic errors in moments and quantiles resulting mainly from bad assumption of the model (model error) unless this model is the normal distribution. Since the estimators by the method of linear moments (L-moments) yield much lower model errors than those by the maximum likelihood, to improve the accuracy of the parameters and quantiles in non-stationary case, a new two-stage methodology of NFFA based on the concept of L-moments was developed. Despite taking advantage of the positive characteristics of L-moments, a new technique also allows to keep the calculations "distribution independent" as long as possible. These two stages consists in (1) least square estimation of trends in mean value and/or in standard deviation and "de-trendisation" of the time series and (2) estimation of parameters and quantiles by means of stationary sample with L-moments method and "re-trendisation" of quantiles. As a result time-dependent quantiles for a given time and return period can be calculated.

The comparative results of Monte Carlo simulations confirmed the superiority of two-stage NFFA methodology over the classical maximum likelihood one. Further analysis of trends in GEV-parent-distributed generic time series by means of both NFFA methods revealed big differences between classical and two-stage estimators of trends got for the same data by the same model (GEV or Gumbel). Additionally, it turned out that the quantiles estimated by the methods of traditional stationary flood frequency analysis equal only to those non-stationary calculated for a strict middle of the time series. It proves that use of traditional stationary methods in conditions of variable regime is too much a simplification and leads to erroneous results. Therefore, when the phenomenon is non-stationary, so should be the methods used for its interpretation.

Citation: Kochanek, K., Strupczewski, W. G., Bogdanowicz, E., Feluch, W., and Markiewicz, I.: Application of a hybrid approach in nonstationary flood frequency analysis – a Polish perspective, Nat. Hazards Earth Syst. Sci. Discuss.,, 2013.
K. Kochanek et al.
Interactive discussionStatus: closed
AC: Author comment | RC: Referee comment | SC: Short comment | EC: Editor comment
Printer-friendly Version - Printer-friendly version      Supplement - Supplement
RC C2134: 'Referee comment', Anonymous Referee #1, 24 Dec 2013 Printer-friendly Version 
AC C2786: 'Reply to teh Referee #1', Krzysztof Kochanek, 04 Mar 2014 Printer-friendly Version Supplement 
RC C2496: 'hydrological hazards', Anonymous Referee #2, 05 Feb 2014 Printer-friendly Version 
AC C2795: 'Reply to teh Referee #2', Krzysztof Kochanek, 04 Mar 2014 Printer-friendly Version Supplement 
K. Kochanek et al.
K. Kochanek et al.


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