The utility of L-moment ratio diagrams for selecting a regional probability distribution

Abstract

L-moment ratio diagrams are increasingly being used in the literature for selecting a probability distribution function for regional frequency analysis. Two graphical methods are often used in the distribution selection process, the sample average and a line of best-fit through the sample L-moment ratios. Examples of homogeneous and heterogeneous regional samples are simulated to illustrate the utility of the two distribution selection methods. Distribution selection for homogeneous regional data is best based on the sample average and not on a line of best-fit through the data points. For very heterogeneous regional data, exhibiting a large range in the distributions shape parameter, the line of best-fit is useful for distribution selection. These results emphasize the importance of using heterogeneity tests in conjunction with L-moment ratio diagrams.