Probability distribution of flood flows in Tunisia

H. Abida (1) , M. Ellouze

1 Department of Earth Sciences [Sfax]

L (Linear) moments are used in identifying regional flood frequency distributions for different zones Tunisia wide. 893 site-years of annual maximum stream flow data from a total of 37 stations with an average record length of 24.14 years are considered. The country is divided into two homogeneous regions (northern and central/southern Tunisia) using a heterogeneity measure, based on the spread of the sample L-moments among the sites in a given region. Then, selection of the corresponding distribution is achieved through goodness-of-fit comparisons in L-moment diagrams and verified using an L-moment based regional test that compares observed to theoretical values of L-skewness and L-kurtosis for various candidate distributions. The distributions used, which represent five of the most frequently used distributions in the analysis of hydrologic extreme variables 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 to the best-fit flood frequency distribution, are distinguished: Northern Tunisia was shown to be represented by the GEV distribution while the GLO distribution gives the best fit in central/southern Tunisia.

Domaines: Interfaces continentales, environnement; Océan, Atmosphère; Sciences de la Terre

H. Abida, M. Ellouze. Probability distribution of flood flows in Tunisia. Hydrology and Earth System Sciences Discussions, 2007, 4 (2), pp.957-981. ⟨hal-00298830⟩