Statewide regression equations for Oklahoma were determined for estimating peak discharge and flood frequency for selected recurrence intervals from 2 to 500 years for ungaged sites on natural unregulated streams. The most significant independent variables required to estimate peak-streamflow frequency for natural unregulated streams in Oklahoma are contributing drainage area, main-channel slope, and mean-annual precipitation. The regression equations are applicable for watersheds with drainage areas less than 2,510 square miles that are not affected by regulation from manmade works.
Limitations on the use of the regression relations and the reliability of regression estimates for natural unregulated streams are discussed. Log-Pearson Type III analysis information, basin and climatic characteristics, and the peak-stream-flow frequency estimates for 251 gaging stations in Oklahoma and adjacent states are listed.
Techniques are presented to make a peak-streamflow frequency estimate for gaged sites on natural unregulated streams and to use this result to estimate a nearby ungaged site on the same stream. For ungaged sites on urban streams, an adjustment of the statewide regression equations for natural unregulated streams can be used to estimate peak-streamflow frequency. For ungaged sites on streams regulated by small floodwater retarding structures, an adjustment of the statewide regression equations for natural unregulated streams can be used to estimate peak-streamflow frequency. The statewide regression equations are adjusted by substituting the drainage area below the floodwater retarding structures, or drainage area that represents the percentage of the unregulated basin, in the contributing drainage area parameter to obtain peak-streamflow frequency estimates.
Abstract
Introduction
Purpose and scope
General description and effects of floodwater retarding structures
Acknowledgments
Estimation of peak-streamflow frequency for gaged sites on natural unregulated streams
Annual peak data
Historical peak streamflows
Low-outlier thresholds
Skew coefficients
Regression equations for estimation of peak-streamflow frequency for ungaged sites on natural unregulated streams
Regression analysis
Selected basin and climatic characteristics
Models investigated
Regression equations
Assumptions and applicability of regression equations
Accuracy and limitations
Application of techniques
Weighted peak-streamflow frequency estimates for gaged sites on natural unregulated streams unregulated streams
Peak-streamflow frequency estimates for ungaged sites near gaged sites on natural unregulated streams unregulated streams
Adjustment for ungaged sites on urban streams
Adjustment for ungaged sites on streams regulated by floodwater retarding structures
Examples of techniques
Weighted peak-streamflow frequency estimates for gaged sites on natural unregulated streams
Peak-streamflow frequency estimates for ungaged sites near gaged sites on natural unregulated streams
Adjustment for ungaged sites on urban streams
Adjustment for ungaged sites on streams regulated by floodwater retarding structures
Summary
Selected references
For more information:
District Chief
U.S. Geological Survey
202 NW 66 St., Bldg 7
Oklahoma City, OK 73116
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