![]() Several distributions were fitted to the regional flood data and index-flood and multiple-regression methods as two regional flood frequency methods were compared. ![]() Homogeneity test was done using L-moments-based measures. Ward’s cluster and L-moments approaches were applied to several sites in the Namak-Lake basin in central Iran to delineate homogeneous regions based on site characteristics. Factor analysis was applied to determine main influencing variables on flood magnitude. Comparing index-flood and multiple-regression analyses based on L-moments was the main objective of this study. In arid and semi-arid regions, the length of records is usually too short to ensure reliable quantile estimates. Only the use of discharge statistics resulted in acceptable predictions.Ĭomparing the index-flood and multiple-regression methods using L-moments As the MAF is unknown at ungauged and short-period measured basins, we tested predicting the MAF using catchments climate-physical characteristics, and discharge statistics, the latter when observations were available for only 8 years. ![]() For larger return periods the prediction capability decreased but could be improved by the use of the GRADEX method. Results showed that if the mean annual flood (MAF), used as index-flood, is known, the index-flood approach performed well for up to 10 years return periods, resulting in 25% mean relative error in prediction. For return periods larger than 10-years the probability distribution of rainfall and discharge volumes were assumed to be asymptotically and exponential-type functions with the same scale parameter from the GRADEX method. For up to 10-years return period, similar shape of the scaled flood frequency curve for catchments with similar flood behaviour was assumed from the index-flood approach. This was achieved by combining two existing flood frequency analysis methods, the regionalization index-flood approach with the GRADEX method. In this study, we tested the usefulness of combining regional discharge and local precipitation data to estimate the event flood volume frequency curve for 63 catchments in Mexico, Central America and the Caribbean. However, such analysis requires of long series of observed discharge data which are often not available in many basins around the world. The index-flood and the GRADEX methods combination for flood frequency analysis.įuentes, Diana Di Baldassarre, Giuliano Quesada, Beatriz Xu, Chong-Yu Halldin, Sven Beven, Keithįlood frequency analysis is used in many applications, including flood risk management, design of hydraulic structures, and urban planning.
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