Comprehensive evaluation of regional flood frequency analysis by L- and LH-moments. I. A re-visit to regional homogeneity |
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| Authors: | Ali Meshgi Davar Khalili |
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| Institution: | (1) Water Engineering Department, College of Agriculture, Shiraz University, Shiraz, Fars, Iran |
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| Abstract: | As part I of a sequence of two papers, previously developed L-moments by Hosking (J R Stat Soc Ser B Methodol 52(2):105–124,
1990), and the LH-moments by Wang (Water Resour Res 33(12):2841–2848, 1997) are re-visited. New relationships are developed for regional homogeneity analysis by the LH-moments, and further establishment
of regional homogeneity is investigated. Previous works of Hosking (J R Stat Soc Ser B Methodol 52(2):105–124, 1990) and Wang (Water Resour Res 33(12):2841–2848, 1997) on L-moments and LH-moments for the generalized extreme value (GEV) distribution are extended to the generalized Pareto
(GPA) and the generalized logistic (GLO) distributions. The Karkhe watershed, located in western Iran is used as a case study
area. Regional homogeneity was investigated by first assuming the entire study area as one regional cluster. Then the entire
study area was designated “homogeneous” by the L-moments (L); and was designated “heterogeneous” by all four levels of the
LH-moments (L1 to L4). The k-means method was used to investigate the case of two regional clusters. All levels of the L- and LH-moments designated the
upper watershed (region A), “homogeneous”, and the lower watershed (region B) “possibly-homogeneous”. The L3 level of the GPA and the L4 level of the GLO were selected for regions A and B, respectively. Wang (Water Resour Res 33(12):2841–2848, 1997) identified a reversing trend in improved performance of the GEV distribution at the LH-moments level of L3 (during the goodness-of-fit test). Similar results were also obtained in this research for the GEV distribution. However,
for the case of the GPA distribution the reversing trend started at L4 for region A; and at L2 for region B. As for the case of the GLO, an improved performance was observed for all levels (moving from L to L4); for both regions. |
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| Keywords: | Regional homogeneity Frequency analysis LH-moments |
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