| Abstract: | A regional frequency analysis was conducted to estimate the depth-duration frequency of precipitation for 12 durations in Oklahoma (15, 30, and 60 minutes; 1, 2, 3, 6, 12, and 24 hours; and 1, 3, and 7 days). Seven selected frequencies, expressed as recurrence intervals, were investigated (2, 5, 10, 25, 50, 100, and 500 years). L-moment statistics were used to summarize depth-duration data and to determine the appropriate statistical distributions. Three different rain-gage networks provided the data (15minute, 1-hour, and 1-day). The 60-minute, and 1-hour; and the 24-hour, and 1-day durations were analyzed separately.
Data were used from rain-gage stations with at least 10-years of record and within Oklahoma or about 50 kilometers into bordering states. Precipitation annual maxima (depths) were determined from the data for 110 15-minute, 141 hourly, and 413 daily stations.
The L-moment statistics for depths for all durations were calculated for each station using unbiased L-mo-ment estimators for the mean, L-scale, L-coefficient of variation, L-skew, and L-kur-tosis. The relation between L-skew and L-kurtosis (L-moment ratio diagram) and goodness-of-fit measures were used to select the frequency distributions. The three-parameter generalized logistic distribution was selected to model the frequencies of 15-, 30-, and 60-minute annual maxima; and the three-parameter generalized extreme-value distribution was selected to model the frequencies of 1-hour to 7-day annual maxima.
The mean for each station and duration was corrected for the bias associated with fixed interval recording of precipitation amounts. The L-scale and spatially averaged L-skew statistics were used to compute the location, scale, and shape parameters of the selected distribution for each station and duration. The three parameters were used to calculate the depth-duration-frequency relations for each station. The precipitation depths for selected frequencies were contoured from weighted depth surfaces to produce maps from which the precipitation depth-duration-frequency curve for selected storm durations can be determined for any site in Oklahoma. |
| Genre: | USGS Numbered Series |
| ProdID: | 30184 |
| Citation Author: | Tortorelli, Robert L.; Rea, Alan; Asquith, William H. |
| Citation Contributing Office: | Oklahoma Water Science Center |
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| Citation Edition: | - |
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| Citation Language: | ENGLISH |
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| Citation LatN: | 0380000 |
| Citation LatS: | 0320000 |
| Citation LonE: | -0930000 |
| Citation LonW: | -1040000 |
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| Citation Phsyical Description: | iii, 113 p. |
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| Citation Public Comments: | Prepared in cooperation with the Oklahoma Department of Transportation |
| Citation Publisher: | U.S. Geological Survey |
| Citation Series: | Water-Resources Investigations Report |
| Citation Series Code: | WRI |
| Citation Series Number: | 99-4232 |
| Citation Search Results Text: | Depth-Duration Frequency of Precipitation for Oklahoma; 1999; WRI; 99-4232; Tortorelli, Robert L.; Rea, Alan; Asquith, William H. |
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| Citation Year: | 1999 |
| Type: | citation/reference |
| Text: | Depth-Duration Frequency of Precipitation for Oklahoma; 1999; WRI; 99-4232; Tortorelli, Robert L.; Rea, Alan; Asquith, William H. |
| URL (THUMBNAIL): | http://pubs.er.usgs.gov/thumbnails/usgs_thumb.jpg |
| URL (INDEX PAGE): | http://pubs.usgs.gov/wri/wri994232/ |
| Date Other: | Wed, 1 May 2002 00:00 -0500 |
| Publisher: | U.S. Geological Survey |
