Regional Flood Frequency Analysis Based on L-Moment Approach (Case Study West Azarbayjan Basins)

Flood estimation with certain frequency is one of the fundamental factors for design ofHydraulic structures, Flood plain, River coastal stabling, Basin management, etc. Accurate estimation offlood frequency discharge increases safety of the structures. L-moment approach was used for floodfrequency analysis in west Azarbayjan province basins. For identifying homogeneous regions, the Wardhierarchical cluster method was used. Site data were used for independent testing of the cluster of the stationfor homogeneity. The west Azarbayjan province divided to four regions. In these regions parameters of theregional frequency distribution were evaluated by L-moment ratios. The L-moment diagram, goodness of fittest, and plotting position methods were used for the selection of appropriate distributions. In westAzarbayjan, Generalized Pareto distribution for region A, Generalized extreme value, Pearson type III andLognormal distributions for region B, Pearson type III, Lognormal, Generalized extreme value distributionsfor region C and Lognormal and Generalized extreme value distribution were appropriate for region D. Therelative Root Mean Square Error (rRMSE) between observed and estimated data in all stations is small.Regional model evaluated for determination of flood discharge magnitude in different frequency by linerand multiple regression method.