Development of Regional Flood Frequency Relationships for Gauged and Ungauged Catchments Using L-Moments

Abstract

For planning, development, and sustainable management of water resources, applications of new and advanced methodologies are essential for design flood estimation. The L-moments are a recent development within statistics and offer significant advantages over ordinary product moments. Regional flood frequency relationships are developed based on the L-moment approach. The annual maximum peak floods data are screened using the discordancy measure (D i }), and homogeneity of the region is tested employing the L-moment-based heterogeneity measure (H). For computing heterogeneity measure H, 500 simulations are performed using the κ-distribution . Twelve frequency distributions namely extreme value (EV1), generalized extreme value (GEV), logistic (LOS), generalized logistic (GLO), normal (NOR), generalized normal (GNO), uniform (UNF), Pearson type-III (PE3), exponential (EXP), generalized Pareto (GPA), κ- (KAP), and five-parameter Wakeby (WAK) are employed. Based on the L-moment ratio diagram and \(|Z_{i}^{\mathrm{dist}}|\)-statistic criteria, GNO is identified as the robust frequency distribution for the study area. For estimation of floods of various return periods for gauged catchments of the study area, the regional flood frequency relationship is developed using the L-moment-based GNO distribution. Also, for estimation of floods of various return periods for ungauged catchments, the regional flood frequency relationships developed for gauged catchments is coupled with the regional relationship between mean annual maximum peak flood and catchment area.