Heterogeneity measures in hydrological frequency analysis: review and new developments
Some regional procedures to estimate hydrological quantiles at ungauged sites, such as the index-flood method, require the delineation of homogeneous regions as a basic step for their application. The homogeneity of these delineated regions is usually tested providing a yes/no decision. However, com...
| Main Authors: | , , |
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| Format: | Article |
| Language: | English |
| Published: |
Copernicus Publications
2017-03-01
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| Series: | Hydrology and Earth System Sciences |
| Online Access: | http://www.hydrol-earth-syst-sci.net/21/1651/2017/hess-21-1651-2017.pdf |
| Summary: | Some regional procedures to estimate hydrological quantiles at
ungauged sites, such as the index-flood method, require the delineation of
homogeneous regions as a basic step for their application. The homogeneity
of these delineated regions is usually tested providing a yes/no decision.
However, complementary measures that are able to quantify the degree of
heterogeneity of a region are needed to compare regions, evaluate the impact
of particular sites, and rank the performance of different delineating
methods. Well-known existing heterogeneity measures are not well-defined for
ranking regions, as they entail drawbacks such as assuming a given
probability distribution, providing negative values and being affected by
the region size. Therefore, a framework for defining and assessing desirable
properties of a heterogeneity measure in the regional hydrological context
is needed. In the present study, such a framework is proposed through a
four-step procedure based on Monte Carlo simulations. Several heterogeneity
measures, some of which commonly known and others which are derived from recent
approaches or adapted from other fields, are presented and developed to be
assessed. The assumption-free Gini index applied on the at-site L-variation
coefficient (L-CV) over a region led to the best results. The measure of the
percentage of sites for which the regional L-CV is outside the confidence
interval of the at-site L-CV is also found to be relevant, as it leads to
more stable results regardless of the regional L-CV value. An illustrative
application is also presented for didactical purposes, through which the
subjectivity of commonly used criteria to assess the performance of
different delineation methods is underlined. |
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| ISSN: | 1027-5606 1607-7938 |