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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.

 


U.S. Department of the Interior, U.S. Geological Survey
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Last modified: Friday, September 16 2005, 04:24:23 PM
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