In cooperation with the Brazos River Authority
Peak-Discharge Frequency and Potential Extreme Peak Discharge for Natural Streams in the Brazos River Basin, Texas
By Timothy H. Raines
U.S. Geological Survey
Water-Resources Investigations Report 98–4178
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Contents
Abstract
Introduction
Purpose and Scope
Physical Setting
Peak-Discharge Frequency for Streamflow-Gaging Stations
Basin Characteristics for Streamflow-Gaging Stations
Peak-Discharge Frequency
Hydrologic Regions
Multiple Regression Equations for Estimation of Peak-Discharge Frequency
Prediction Intervals
Application of Regression Equations and Prediction Intervals
Sites At or Near Streamflow-Gaging Stations
Sites Not At or Near Streamflow-Gaging Stations
Potential Extreme Peak Discharge
Summary
References Cited
Plate
1. | Map showing hydrologic regions and locations of streamflow-gaging stations in and near the Brazos River Basin, Texas |
Figures
1. | Map showing location of the Brazos River Basin, Texas | |
2–7. | Graphs showing relation of 100-year peak discharge to: | |
2. | 2-year, 24-hour maximum precipitation | |
3. | Mean annual precipitation | |
4. | Contributing drainage area | |
5. | Stream length | |
6. | Basin shape | |
7. | Average stream slope | |
8–13. | Graphs showing relation of: | |
8. | Stream length to contributing drainage area | |
9. | Basin shape to contributing drainage area | |
10. | Average stream slope to contributing drainage area | |
11. | Stream length to basin shape | |
12. | Stream length to average stream slope | |
13. | Basin shape to average stream slope | |
14–16. | Graphs showing potential extreme peak discharge for: | |
14. | Hydrologic region 1, Brazos River Basin, Texas | |
15. | Hydrologic region 2, Brazos River Basin, Texas | |
16. | Hydrologic region 3, Brazos River Basin, Texas | |
17. | Graph showing potential extreme peak discharge curves for hydrologic regions, Brazos River Basin, Texas |
Tables
1. | Peak-discharge frequency estimates, analysis information, and basin characteristics for stations with at least 8 years of annual peak-streamflow data from natural streams in and near the Brazos River Basin, Texas |
2. | Regression equations for estimation of peak-discharge frequency for hydrologic regions of the Brazos River Basin, Texas |
3. | Covariance matrices and critical values for prediction intervals of regression equations for estimation of peak-discharge frequency for hydrologic regions of the Brazos River Basin, Texas |
4. | Measured extreme peak discharges for sites with and without streamflow-gaging stations in natural streams in and near the Brazos River Basin, Texas |
Abstract
The 2-, 5-, 10-, 25-, 50-, and 100-year peak discharges were estimated for 186 streamflow-gaging stations with at least 8 years of data for natural streams in and near the Brazos River Basin, Texas. Multiple regression equations were developed to estimate peak-discharge frequency for the 2-, 5-, 10-, 25-, 50-, and 100-year recurrence intervals for each of three hydrologic regions that compose the Brazos River Basin. The equations for each region are a function of significant basin characteristics (explanatory variables). The significant explanatory variables among six that were tested are the contributing drainage area and stream slope for regions 1 and 2 and the contributing drainage area for region 3. For the three sets of equations, the coefficient of determination ranges from 0.59 to 0.93, and the standard error ranges from 0.184 to 0.391 log units. A larger coefficient of determination and a lower standard error generally are associated with the equations for hydrologic regions 2 and 3. Statistics from the regression analysis allow computation of the prediction interval associated with a given significance level for a peak-discharge frequency estimate. The regression equations can be used to estimate peak discharges for sites at, near, or away from sites with streamflow-gaging stations.
The potential extreme peak-discharge curves as related to contributing drainage area were estimated for each of the three hydrologic regions from measured extreme peaks of record at 186 sites with streamflow-gaging stations and from measured extreme peaks at 37 sites without streamflow-gaging stations in and near the Brazos River Basin. The potential extreme peak-discharge curves generally are similar for hydrologic regions 1 and 2, and the curve for region 3 consistently is below the curves for regions 1 and 2, which indicates smaller peak discharges.
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