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Stochastic Hydrology and Hydraulics

, Volume 11, Issue 1, pp 51–63 | Cite as

Chowdhury and Stedinger's approximate confidence intervals for design floods for a single site

  • R. Whitley
  • T. V. HromadkaII
Originals

Abstract

A basic problem in hydrology is computing confidence levels for the value of the T-year flood when it is obtained from a Log Pearson III distribution in terms of estimated mean, estimated standard deviation, and estimated skew. In an important paper Chowdhury and Stedinger [1991] suggest a possible formula for approximate confidence levels, involving two functions previously used by Stedinger [1983] and a third function, λ, for which asymptotic estimates are given. This formula is tested [Chowdhury and Stedinger, 1991] by means of simulations, but these simulations assume a distribution for the sample skew which is not, for a single site, the distribution which the sample skew is forced to have by the basic hypothesis which underlies all of the analysis, namely that the maximum discharges have a Log Pearson III distribution. Here we test these approximate formulas for the case of data from a single site by means of simulations in which the sample skew has the distribution which arises when sampling from a Log Pearson III distribution. The formulas are found to be accurate for zero skew but increasingly inaccurate for larger common values of skew. Work in progress indicates that a better choice of λ can improve the accuracy of the formula.

Keywords

Confidence Interval Waste Water Water Management Water Pollution Stochastic Process 
These keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.

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Copyright information

© Springer-Verlag 1997

Authors and Affiliations

  • R. Whitley
    • 1
  • T. V. HromadkaII
    • 2
  1. 1.Department of MathematicsUniversity of CaliforniaIrvineUSA
  2. 2.Newport BeachUSA

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