Analytical approach to quantile estimation in regional frequency analysis based on fuzzy framework

Basu, Bidroha and Srinivas, VV (2015) Analytical approach to quantile estimation in regional frequency analysis based on fuzzy framework. In: JOURNAL OF HYDROLOGY, 524 . pp. 30-43.

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Abstract

Regional frequency analysis is widely used for estimating quantiles of hydrological extreme events at sparsely gauged/ungauged target sites in river basins. It involves identification of a region (group of watersheds) resembling watershed of the target site, and use of information pooled from the region to estimate quantile for the target site. In the analysis, watershed of the target site is assumed to completely resemble watersheds in the identified region in terms of mechanism underlying generation of extreme event. In reality, it is rare to find watersheds that completely resemble each other. Fuzzy clustering approach can account for partial resemblance of watersheds and yield region(s) for the target site. Formation of regions and quantile estimation requires discerning information from fuzzy-membership matrix obtained based on the approach. Practitioners often defuzzify the matrix to form disjoint clusters (regions) and use them as the basis for quantile estimation. The defuzzification approach (DFA) results in loss of information discerned on partial resemblance of watersheds. The lost information cannot be utilized in quantile estimation, owing to which the estimates could have significant error. To avert the loss of information, a threshold strategy (TS) was considered in some prior studies. In this study, it is analytically shown that the strategy results in under-prediction of quantiles. To address this, a mathematical approach is proposed in this study and its effectiveness in estimating flood quantiles relative to DFA and TS is demonstrated through Monte-Carlo simulation experiments and case study on Mid-Atlantic water resources region, USA. (C) 2015 Elsevier B.V. All rights reserved.

Item Type:	Journal Article
Publication:	JOURNAL OF HYDROLOGY
Publisher:	ELSEVIER SCIENCE BV
Additional Information:	Copy right for this article belongs to the ELSEVIER SCIENCE BV, PO BOX 211, 1000 AE AMSTERDAM, NETHERLANDS
Keywords:	Regionalization; Regional flood frequency analysis; Fuzzy cluster analysis; Mid-Atlantic water resources region, USA
Department/Centre:	Division of Mechanical Sciences > Civil Engineering
Date Deposited:	16 Jun 2015 05:18
Last Modified:	16 Jun 2015 05:18
URI:	http://eprints.iisc.ac.in/id/eprint/51699

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