Development of Regression Equations for the Estimation of Flood Flows at Ungaged Streams in Pennsylvania

Scientific Investigations Report 2019-5094
Prepared in cooperation with the Federal Emergency Management Agency and the Pennsylvania Department of Transportation
By:  and 



Regression equations, which may be used to estimate flood flows at select annual exceedance probabilities, were developed for ungaged streams in Pennsylvania. The equations were developed using annual peak flow data through water year 2015 and basin characteristics for 285 streamflow gaging stations across Pennsylvania and surrounding states. The streamgages included active and discontinued continuous-record stations, as well as crest-stage partial-record stations, and required a minimum of 10 years of annual peak streamflow data for inclusion in the study. Explanatory variables significant at the 95-percent confidence level for one or more regression equations included the following basin characteristics: drainage area, maximum basin elevation, mean basin slope, percent storage, and the percentage of carbonate bedrock within a basin. The State was divided into five regions, and regional regression equations were developed to estimate flood flows associated with the 50-, 20-, 10-, 4-, 2-, 1-, 0.5-, and 0.2-percent annual exceedance probabilities (which correspond to the 2-, 5-, 10-, 25-, 50-, 100-, 200-, and 500-year recurrence intervals, respectively). Although the regression equations can be used to estimate the magnitude of flood flows for most streams in the State, they are not valid for streams with drainage areas generally greater than 1,500 square miles or with substantial regulation, diversion, or mining activity within the basin. The regional regression equations will be incorporated into the U.S. Geological Survey StreamStats application (

Additionally, annual peak flow data for 356 streamgages initially considered for inclusion in the analysis for development of updated flood-flow regression equations were analyzed for the existence of trends; estimates of flood-flow magnitude and frequency were also computed for these streamgages. Estimates of flood-flow magnitude and frequency for streamgages substantially affected by upstream regulation are also presented.

Suggested Citation

Roland, M.A., and Stuckey, M.H., 2020, Development of regression equations for the estimation of flood flows at ungaged streams in Pennsylvania (ver. 1.1, December 2020): U.S. Geological Survey Scientific Investigations Report 2019–5094, 36 p., [Supersedes USGS Scientific Investigations Report 2008–5102]

ISSN: 2328-0328 (online)

Study Area

Table of Contents

  • Abstract
  • Introduction
  • Streamgage Selection and Data Analysis
  • Basin and Climate Characteristics
  • Development of Regression Equations
  • Estimating Flood Flows at Ungaged Sites Near a Streamgage
  • General Guidelines for the Estimation of Magnitude and Frequency of Flood Flows
  • Summary
  • Acknowledgments
  • References Cited
  • Appendixes 1, 2, and 3
Publication type Report
Publication Subtype USGS Numbered Series
Title Development of regression equations for the estimation of flood flows at ungaged streams in Pennsylvania
Series title Scientific Investigations Report
Series number 2019-5094
DOI 10.3133/sir20195094
Edition Version 1.0: October 2019; Version 1.1: December 2020
Year Published 2019
Language English
Publisher U.S. Geological Survey
Publisher location Reston, VA
Contributing office(s) Pennsylvania Water Science Center
Description Report: vi, 36 p.; Appendices 1-3; Data Release
Public Comments Scientific Investigations Report 2019-5094 supersedes Scientific Investigations Report 2008–5102.
Country United States
State Pennsylvania
Online Only (Y/N) Y
Additional Online Files (Y/N) Y
Google Analytic Metrics Metrics page
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