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Characterization of Peak Streamflows and Flooding in Select Areas of Pennsylvania from the Remnants of Hurricane Ida, September 1–2, 2021

Scientific Investigations Report 2023-5086
Prepared in cooperation with the Federal Emergency Management Agency
By: , , and 
https://doi.org/10.3133/sir20235086

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Abstract

Pennsylvania experienced heavy rainfall on September 1 and 2, 2021, as the remnants of Hurricane Ida swept over parts of the State. Much of eastern and south-central Pennsylvania received 5 to 10 inches of rain, and most of the rainfall fell within little more than 6 hours. Southeastern Pennsylvania experienced widespread, substantial flooding, and the city of Philadelphia and surrounding areas were particularly affected by the flooding. U.S. Geological Survey (USGS) streamgages registered peak streamflows of record at 19 locations, and 52 locations experienced top 5 peak streamflows for the period of record and an annual exceedance probability estimate of at least 10 percent. During this September 2021 flood event, USGS personnel made over 60 streamflow measurements at streamgages in Pennsylvania using direct and indirect methods. Many of those streamflow measurements were made to verify or improve the accuracy, extent, or development of new stage-streamflow relations at streamgages operated by the USGS. After the floodwaters receded, USGS personnel identified and documented a total of 338 high-water marks in Pennsylvania, noting such things as their general description, location, height above land surface, and quality. Many of these high-water marks were used to create five flood-documentation maps for selected communities in southeastern Pennsylvania that experienced substantial flooding because of the remnants of Hurricane Ida. Digital datasets of the inundated areas, mapped boundaries, and water depth are available (Stuckey and Conlon, 2023).

Suggested Citation

Stuckey, M.H., Conlon, M.D., and Weaver, M.R., 2023, Characterization of peak streamflows and flooding in select areas of Pennsylvania from the remnants of Hurricane Ida, September 1–2, 2021 (ver. 1.1, September 28, 2023): U.S. Geological Survey Scientific Investigations Report 2023–5086, 28 p., https://doi.org/10.3133/sir20235086.

ISSN: 2328-0328 (online)

Study Area

Table of Contents

  • Acknowledgments
  • Abstract
  • Introduction
  • Weather Conditions Before and During the Flood
  • Methods
  • Estimated Magnitudes and Exceedance Probabilities for Peak Streamflows
  • Flood-Documentation Maps
  • Flood Damages
  • Summary
  • References Cited
Publication type Report
Publication Subtype USGS Numbered Series
Title Characterization of peak streamflows and flooding in select areas of Pennsylvania from the remnants of Hurricane Ida, September 1–2, 2021
Series title Scientific Investigations Report
Series number 2023-5086
DOI 10.3133/sir20235086
Edition Version 1.0: September 7, 2023; Version 1.1: September 28, 2023
Year Published 2023
Language English
Publisher U.S. Geological Survey
Publisher location Reston, VA
Contributing office(s) Pennsylvania Water Science Center
Description Report: vii, 28 p.; Data Release
Country United States
State Pennsylvania
Online Only (Y/N) Y
Additional Online Files (Y/N) N
Google Analytic Metrics Metrics page
Additional publication details