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Water-Resources Investigations Report 79–83

Prepared in cooperation with
New York State Department of Transportation and
New York State Department of Environmental Conservation

Techniques for estimating magnitude and frequency of floods on rural unregulated streams in New York State excluding Long Island

By Thomas J. Zembrzuski, Jr., and Bernard Dunn

ABSTRACT

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Techniques are presented for estimating the magnitude and frequency of floods at ungaged sites on unregulated rural streams in New York, excluding Long Island. The discharge-frequency data and basin characteristics of 220 stream-gaging stations in New York and adjacent States were used in developing multiple linear regression equations for floods ranging in recurrence interval from 2 to 100 years. Separate equations were developed for northern, southeastern, and western New York. Standard errors of estimate of the 100-year flood range from 32.9 percent in the southeastern region to 42.8 percent in the western region. Drainage area is the independent variable needed in all equations; other variables needed, depending on region, are main-channel slope, storage index, and mean annual precipitation.

A method is given for obtaining improved discharge-frequency relationships at gaged sites by weighting log-Pearson type III and regression estimates according to their variances.

Basin characteristics, log-Pearson type III statistics, and regression and weighted estimates of the frequency-discharge relationship, are tabulated for the gaging stations used in the regression analyses.

Posted March 5, 2010

For additional information contact:
Director, New York Water Science Center
U.S. Geological Survey
425 Jordan Road
Troy, NY 12180
http://ny.usgs.gov/

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Suggested citation:

Zembrzuski, Thomas J., Jr.; and Dunn, Bernard., 1979, Techniques for estimating magnitude and frequency of floods on rural unregulated streams in New York State excluding Long Island: U.S. Geological Survey Water-Resources Investigations Report 79-83, 72 p.



Contents

Conversion factors and abbreviations

Abstract

Introduction

Previous studies

Acknowledgments

Application of techniques

Gaged sites

Ungaged sites

Ungaged sites on gaged streams

Limitations of procedure

Examples of computations

Analytical techniques

Annual peak-discharge data

Discharge-frequency relationships

Regional regression analysis

Improved flood-frequency estimates at gaged sites

Summary and suggestions for future study

Selected references



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