Estimating generalized skew of the log-Pearson Type III distribution for annual peak floods in Illinois
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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. (
Study Area
| Publication type | Report |
|---|---|
| Publication Subtype | USGS Numbered Series |
| Title | Estimating generalized skew of the log-Pearson Type III distribution for annual peak floods in Illinois |
| Series title | Water-Resources Investigations Report |
| Series number | 86-4008 |
| DOI | 10.3133/wri864008 |
| Year Published | 1987 |
| Language | English |
| Publisher | U.S. Geological Survey |
| Description | v, 42 p. |
| Country | United States |
| State | Illinois |
| Google Analytic Metrics | Metrics page |