Flood frequency analysis of Turkey using L-moments method

Abstract

Abstract:The index flood procedure coupled with the L-moments method is applied to the annual flood peaks data taken at all streamgauging stations in Turkey having at least 15-year-long records. First, screening of the data is done based on the discordancy measure (D i ) in terms of the L-moments. Homogeneity of the total geographical area of Turkey is tested using the L-moments based heterogeneity measure, H, computed on 500 simulations generated using the four parameter Kappa distribution. The Lmoments analysis of the recorded annual flood peaks data at 543 gauged sites indicates that Turkey as a whole is hydrologically heterogeneous, and 45 of 543 gauged sites are discordant which are discarded from further analyses. The catchment areas of these 543 sites vary from 9Ð9 to 75121 km 2 and their mean annual peak floods vary from 1Ð72 to 3739Ð5 m 3 s 1 . The probability distributions used in the analyses, whose parameters are computed by the L-moments method are the general extreme values (GEV), generalized logistic (GLO), generalized normal (GNO), Pearson type III (PE3), generalized Pareto (GPA), and fiveparameter Wakeby (WAK). Based on the L-moment ratio diagrams and the jZ dist j-statistic criteria, the GEV distribution is identified as the robust distribution for the study area (498 gauged sites). Hence, for estimation of flood magnitudes of various return periods in Turkey, a regional flood frequency relationship is developed using the GEV distribution. Next, the quantiles computed at all of 543 gauged sites by the GEV and the Wakeby distributions are compared with the observed values of the same probability based on two criteria, mean absolute relative error and determination coefficient. Results of these comparisons indicate that both distributions of GEV and Wakeby, whose parameters are computed by the L-moments method, are adequate in predicting quantile estimates.

Hydrological regionalization of maximum stream flows using an approach based on L-moments

“…The good applicability of the GEV model, which has shape (к), scale (α) and position (β) parameters, was also observed by Seckin, Haktanir and Yurtal (2011) as to the analysis of maximum stream flows in Turkey, where the model was the best adjusted to 498 of the 543 gauging stations considered. Malekinezhad, Nachtnebel and Klik (2011), comparing five 3-parameter PDFs, found that the GEV model was the only suitable for all the 3 homogeneous regions identified in the Namak-Lake basin, central Iran.…”

“…GEV and Kappa. The improved estimate of maximum hydrological variables resulting from the application of multiparameter PDFs, compared to traditional two-parameter ones, i.e., Normal, LN-2P, Gumbel and Gamma, is widely demonstrated in studies conducted in various regions of the world (EATON; CHURCH; HAM, 2002;KJELDSEN;SMITHERS;SCHULZE, 2002;KUMAR et al, 2003;CHATTERJEE, 2005;NOTO;LA LOGGIA, 2009;SECKIN;HAKTANIR;YURTAL, 2011;BESKOW et al, 2015). The evaluation of traditional and multiparameter PDFs for the adjustment of annual maximum stream flow series as performed in this study, corroborates the findings of Beskow et al (2015), who reported on the importance of the analysis of various theoretical PDFs, from the simplest to those with multiparameters, in order to obtain that which best represents the frequency distribution of the sample.…”

“…In a study in the United States on flooding in the twentieth century, considering only outlets with over 100 years of monitoring, Villarini et al (2009) found that LN and Gamma functions, both with 2 parameters, had performance superior than Gumbel and Weibull functions. However, it should be pointed out, as reported by Seckin, Haktanir and Yurtal (2011), that, in addition to the suitability of the PDFs, the regionalization of maximum stream flows involves the identification of hydrologically homogenous regions.…”

“…Thus, also according to these researchers, a region is considered homogeneous if all the PDFs adjusted to the historical series are similar to each other (HOSKING; WALLIS, 1997). The measure of regional heterogeneity, H, presented by Hosking and Wallis (1997), has been widely used in scientific studies of hydrological regionalization involving different variables of interest (NOTO; LA LOGGIA, 2009;GAUME et al, 2010;SECKIN;HAKTANIR;YURTAL, 2011;BESKOW et al, 2016b).…”

Adana Ve Çevre İllerde Gözlenen Yillik Maksi̇mum Yağişlarin Bölgesel Frekans Anali̇zi̇

“…[14], Naghavi ve Yu [15], Şorman [16], Seckin [17] Seckin vd. [18] Seckin vd. [19], Saf [20], Dodangeh vd.…”