Coupling of Nonparametric Frequency and L‐moment Analyses for Mixed Distribution Identification¹

Both L‐moment and nonparametric frequency analyses were performed on a series of annual maximum floods from New Brunswick, Canada. The L‐moment analysis concluded that the data were generated from a unimodal Generalized Extreme Value (GEV) distribution. However, the nonparametric frequency analysis indicated that a majority of stations followed nonunimodal mixed distributions since peak flows occur during different seasons and are the result of different generating mechanisms. The coupling of L‐moment and nonparametric analyses facilitates mixed distribution identification. Thus, the nonparametric method helps in identifying underlying probability distribution, especially when samples arise from mixed distributions.