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Flood-Frequency Estimates for Kentucky Streamgages Based on Data Through Water Year 2021 and Results of Updating the Fundamental Layers in Kentucky StreamStats

Scientific Investigations Report 2026-5036
Prepared in cooperation with the Kentucky Transportation Cabinet
By: , , , and 
https://doi.org/10.3133/sir20265036

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Abstract

The U.S. Geological Survey, in cooperation with the Kentucky Transportation Cabinet, analyzed flood-frequency statistics for streamgages in Kentucky. Using annual peak-flow data through water year 2021, flood-frequency estimates were computed for 261 streamgages, including unregulated and regulated sites as well as sites with mixed regulation records. Methods followed those outlined in “Guidelines for Determining Flood Flow Frequency—Bulletin 17C” (U.S. Geological Survey Techniques and Methods 4–B5). These estimates included flows corresponding to annual exceedance probabilities of 50, 20, 10, 4, 2, 1, and 0.2 percent. Temporal trend analyses using the Mann-Kendall test indicated that 18 percent of unregulated streamgages with (1) at least 30 years of peak-flow record and (2) peak-flow record at least as recent as water year 2000 showed statistically significant trends, most of which were weak to moderate increases in peak flows. Concurrently, the fundamental geospatial datasets that support the Kentucky StreamStats application were updated by using high-resolution digital elevation models and hydrography datasets to derive flow direction, flow accumulation, and stream definition rasters. Comparisons of regression-based flood-frequency models using the old and new layers demonstrated consistent results, with a statewide root-mean-square error of 0.019, in the base-10 logarithm of cubic feet per second. Furthermore, to assess model performance, flood-frequency estimates made by using the updated layers and previously published regression-based models were compared to flood-frequency estimates newly computed by following Bulletin 17C. This analysis showed the models performed adequately for most Kentucky stream locations. The updated statistics and geospatial layers provide stakeholders with more accurate, current data for flood-risk assessment, infrastructure design, and water-resource management.

Suggested Citation

VonIns, B.L., Webber, J.J., Follette, D.D., and Jeffords, T.G., 2026, Flood-frequency estimates for Kentucky streamgages based on data through water year 2021 and results of updating the fundamental layers in Kentucky StreamStats: U.S. Geological Survey Scientific Investigations Report 2026–5036, 12 p., https://doi.org/10.3133/sir20265036.

ISSN: 2328-0328 (online)

Table of Contents

  • Acknowledgments
  • Abstract
  • Introduction
  • Purpose and Scope
  • Description of Study Area
  • Computation of Flood-Frequency Statistics at Gaged Sites
  • Tests for Temporal Trends in Peak Flows
  • Fundamental Layers Update
  • Assessment of Regression Models
  • Summary
  • References Cited
Publication type Report
Publication Subtype USGS Numbered Series
Title Flood-frequency estimates for Kentucky streamgages based on data through water year 2021 and results of updating the fundamental layers in Kentucky StreamStats
Series title Scientific Investigations Report
Series number 2026-5036
DOI 10.3133/sir20265036
Publication Date June 30, 2026
Year Published 2026
Language English
Publisher U.S. Geological Survey
Publisher location Reston, VA
Contributing office(s) Ohio-Kentucky-Indiana Water Science Center
Description Report: vii, 12 p.; Data Releases
Online Only (Y/N) Y
Additional Online Files (Y/N) N
Additional publication details