Flood Frequency Estimates and Documented and Potential Extreme Peak Discharges in Oklahoma


U.S. Geological Survey Water-Resources Investigations Report 01–4152


By Robert L. Tortorelli and Lan P. McCabe


This report is available as a pdf.


Knowledge of the magnitude and frequency of floods is required for the safe and economical design of highway bridges, culverts, dams, levees, and other structures on or near streams; and for flood plain management programs. Flood frequency estimates for gaged streamflow sites were updated, documented extreme peak discharges for gaged and miscellaneous measurement sites were tabulated, and potential extreme peak discharges for Oklahoma streamflow sites were estimated. Potential extreme peak discharges, derived from the relation between documented extreme peak discharges and contributing drainage areas, can provide valuable information concerning the maximum peak discharge that could be expected at a stream site. Potential extreme peak discharge is useful in conjunction with flood frequency analysis to give the best evaluation of flood risk at a site.


Peak discharge and flood frequency for selected recurrence intervals from 2 to 500 years were estimated for 352 gaged streamflow sites. Data through 1999 water year were used from streamflow-gaging stations with at least 8 years of record within Oklahoma or about 25 kilometers into the bordering states of Arkansas, Kansas, Missouri, New Mexico, and Texas. These sites were in unregulated basins, and basins affected by regulation, urbanization, and irrigation.


Documented extreme peak discharges and associated data were compiled for 514 sites in and near Oklahoma, 352 with streamflow-gaging stations and 162 at miscellaneous measurements sites or streamflow-gaging stations with short record, with a total of 671 measurements.The sites are fairly well distributed statewide, however many streams, large and small, have never been monitored.


Potential extreme peak-discharge curves were developed for streamflow sites in hydrologic regions of the state based on documented extreme peak discharges and the contributing drainage areas.


Two hydrologic regions, east and west, were defined using 98 degrees 15 minutes longitude as the dividing line.




Purpose and scope


Flood frequency estimates for gaged streamflow sites

Annual peak data

Historical peak discharges

Low-outlier thresholds

Skew coefficients

Documented extreme peak discharges

Potential extreme peak discharges


Selected references

Supplemental information

Table 1. Documented and potential extreme peak discharges and flood frequency estimates for selected streamflow-gaging stations with at least 8 years of annual peak-discharge data from unregulated, regulated, and urban basins within and near Oklahoma

Table 2. Documented and potential extreme peak discharges for selected indirect measurement sites without streamflow-gaging stations and streamflow-gaging stations with short periods in basins within Oklahoma .

For additional information write to:


District Chief

U.S. Geological Survey

202 NW 66 St. Bldg. 7

Oklahoma City, OK 73116


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Denver Federal Center

Denver, CO 80225


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