Assessment of regional floods using L-moments approach: The case of the river Nile

In this study, a regional flood frequency analysis has been carried out, using the index flood L-moments approach. Annual maximum stream flood data observed at 14 gauged sites on the Nile River tributaries (Blue Nile, White Nile, and Atbara River) are investigated. The aim of the study is to investigate and derive hydrologically homogeneous region or regions and to identify and establish the regional statistical distribution. To this end, five distribution functions are used, namely: generalized pareto, generalized extreme-value, generalized logistic, generalized normal, and Pearson type-3 distributions. Analyses have shown that 8 sites form a hydrologically homogeneous region, and this region follows a generalized logistic (GLO) distribution. Furthermore, the other remaining two regions (possibly heterogeneous and definitely heterogeneous) are also defined. Regional dimensionless growth curves for the identified three regions are derived. Results are assessed on the basis of relative RMSE% and relative BIAS% through the use of Monte Carlo simulation.