L (Linear) moments are used in identifying regional flood frequencydistributions for different zones Tunisia wide. 1134 site-years of annualmaximum stream flow data from a total of 42 stations with an average recordlength of 27 years are considered. The country is divided into twohomogeneous regions (northern and central/southern Tunisia) using aheterogeneity measure, based on the spread of the sample L-moments among thesites in a given region. Then, selection of the corresponding distributionis achieved through goodness-of-fit comparisons in L-moment diagrams andverified using an L moment based regional test that compares observed totheoretical values of L-skewness and L-kurtosis for various candidatedistributions. The distributions used, which represent five of the mostfrequently used distributions in the analysis of hydrologic extremevariables are: (i) Generalized Extreme Value (GEV), (ii) Pearson Type III(P3), (iii) Generalized Logistic (GLO), (iv) Generalized Normal (GN), and(v) Generalized Pareto (GPA) distributions. Spatial trends, with respect tothe best-fit flood frequency distribution, are distinguished: NorthernTunisia was shown to be represented by the GNO distribution while the GNOand GEV distributions give the best fit in central/southern Tunisia.
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