Estimating generalized skew of the log-Pearson Type III distribution for annual peak floods in Illinois

Oberg, Kevin A.; Mades, Dean M.

Abstract:

Four techniques for estimating generalized skew in Illinois were evaluated: (1) a generalized skew map of the US; (2) an isoline map; (3) a prediction equation; and (4) a regional-mean skew. Peak-flow records at 730 gaging stations having 10 or more annual peaks were selected for computing station skews. Station skew values ranged from -3.55 to 2.95, with a mean of -0.11. Frequency curves computed for 30 gaging stations in Illinois using the variations of the regional-mean skew technique are similar to frequency curves computed using a skew map developed by the US Water Resources Council (WRC). Estimates of the 50-, 100-, and 500-yr floods computed for 29 of these gaging stations using the regional-mean skew techniques are within the 50% confidence limits of frequency curves computed using the WRC skew map. Although the three variations of the regional-mean skew technique were slightly more accurate than the WRC map, there is no appreciable difference between flood estimates computed using the variations of the regional-mean technique and flood estimates computed using the WRC skew map. (Peters-PTT)

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USGS Numbered Series

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28921

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Oberg, Kevin A.; Mades, Dean M.

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ENGLISH

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v, 42 p. :ill., maps ;28 cm.

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U.S. Geological Survey, Water Resources Division,

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Water-Resources Investigations Report

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WRI

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86-4008

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Estimating generalized skew of the log-Pearson Type III distribution for annual peak floods in Illinois; 1987; WRI; 86-4008; Oberg, Kevin A.; Mades, Dean M.

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1987

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citation/reference

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Estimating generalized skew of the log-Pearson Type III distribution for annual peak floods in Illinois; 1987; WRI; 86-4008; Oberg, Kevin A.; Mades, Dean M.