No abstract

No abstract

No abstract

The scale-adjusted probaMity density functions of the two-parameter gamma and the three-parameter beta distributions were shown to fit reasonably well to ten observed unit hydrographs in Anatolia, the gamma exhibiting slightly better fits. As a result, a method making use of this curve is suggested for the synthetic unit hydrograph. Bons résultats obtenus avec les distributions gamma à deux paramètres et béta à trois paramètres pour la génération dTrydrogrammes unitaires synthétiques en Anatolie Résumé Le fonction de densité de probabilité gamma à deux paramètres et la fonction béta à trois paramètres sont avérés bien adaptés à dix hydrogrammes unitaires en Anatolie; la fonction gamma s'adapte mieux aux hydrogrammes. En conséquence on propose un méthode utilisant cette courbe pour les hydrogrammes unitaires synthétiques.

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.

No abstract

No abstract

No abstract