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U.S. GEOLOGICAL SURVEY
Scientific Investigations Report 2007-5158
Version 4.0, March 10, 2008 Revision History

Methods for Estimating Magnitude and Frequency of Peak Flows for Natural Streams in Utah

Prepared in cooperation with
UTAH DEPARTMENT OF TRANSPORTATION AND THE UTAH DEPARTMENT OF NATURAL RESOURCES,
DIVISIONS OF WATER RIGHTS AND WATER RESOURCES


By Terry A. Kenney, Chris D. Wilkowske, and Shane J. Wright

Abstract

Estimates of the magnitude and frequency of peak streamflows is critical for the safe and cost-effective design of hydraulic structures and stream crossings, and accurate delineation of flood plains. Engineers, planners, resource managers, and scientists need accurate estimates of peak-flow return frequencies for locations on streams with and without streamflow-gaging stations. The 2-, 5-, 10-, 25-, 50-, 100-, 200-, and 500-year recurrence-interval flows were estimated for 344 unregulated U.S. Geological Survey streamflow-gaging stations in Utah and nearby in bordering states. These data along with 23 basin and climatic characteristics computed for each station were used to develop regional peak-flow frequency and magnitude regression equations for 7 geohydrologic regions of Utah. These regression equations can be used to estimate the magnitude and frequency of peak flows for natural streams in Utah within the presented range of predictor variables. Uncertainty, presented as the average standard error of prediction, was computed for each developed equation. Equations developed using data from more than 35 gaging stations had standard errors of prediction that ranged from 35 to 108 percent, and errors for equations developed using data from less than 35 gaging stations ranged from 50 to 357 percent.

Contents

Abstract
Introduction

Purpose and Scope
Acknowledgments
Previous Studies
Description of Utah

Flooding in Utah

Envelope Curves

Computation of Peak Flow from Gaged Sites
Methods for Estimating Frequency of Peak Flows at Gaged Sites

Frequency of Peak Flows at Gaged Sites
Frequency of Peak Flows at Ungaged Sites that are Near Gaged Sites on the Same Stream

Regional Regression Method for Estimating Frequency of Peak Flows for Ungaged Sites

Geohydrologic Regionalization of Utah
Basin and Climatic Characteristic
Regional Regression Analysis
Regional Regression Results
Limitations of Regional Regression Equations

StreamStats Web-Based Computer Program
Summary
References Cited
Appendix

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Send questions or comments about this report to the author, Terry A. Kenney, (801) 908-5046.

For more information about USGS activities in Utah, visit the USGS Utah Water Science Center home page.