Magnitude and Frequency of Floods in Alabama, 2015

Scientific Investigations Report 2020-5032
Alabama Department of Transportation



To improve flood-frequency estimates at rural streams in Alabama, annual exceedance probability flows at gaged locations and regional regression equations used to estimate annual exceedance probability flows at ungaged locations were developed by using current geospatial data, new analytical methods, and annual peak-flow data through September 2015 at 242 streamgages in Alabama and surrounding States. The regional regression equations were derived from statistical analyses of annual peak-flow data and basin characteristics for a subset of 217 streamgages. Four flood regions were identified based on residuals from the regional regression analyses and contain sites with similar basin characteristics. A separate set of equations was derived for estimating flood frequency and magnitude for small rural streams using a subset of 40 small basin streamgages. A large river analysis was also completed for 14 selected large-river streamgages in Alabama. Annual exceedance probability flows presented in this report reflect additional streamflow data collected since the previous study of flood magnitude and frequency in Alabama, which included streamflow through September 2003.

Suggested Citation

Anderson, B.T., 2020, Magnitude and frequency of floods in Alabama, 2015: U.S. Geological Survey Scientific Investigations Report 2020–5032, 148 p.,

ISSN: 2328-0328 (online)

ISSN: 2328-031X (print)

Study Area

Table of Contents

  • Acknowledgments
  • Abstract
  • Introduction
  • Data Compilation
  • Flood-Frequency Analysis
  • Flood-Frequency Estimates at Streamgages in Alabama
  • Flood-Frequency Estimates at Ungaged Locations on Gaged Streams
  • Flood-Frequency Estimates at Locations on Ungaged Streams
  • Accuracy and Limitations of Regional Regression Equations
  • Summary and Conclusions
  • References Cited
  • Appendix 1
  • Appendix 2
Publication type Report
Publication Subtype USGS Numbered Series
Title Magnitude and frequency of floods in Alabama, 2015
Series title Scientific Investigations Report
Series number 2020-5032
DOI 10.3133/sir20205032
Year Published 2020
Language English
Publisher U.S. Geological Survey
Publisher location Reston, VA
Contributing office(s) Lower Mississippi-Gulf Water Science Center
Description Report: vii, 148 p.; 1 Plate: 20.00 x 30.00 inches; Data Release
Country United States
State Alabama
Online Only (Y/N) N
Google Analytic Metrics Metrics page
Additional publication details