Magnitude and frequency of floods for rural streams in Georgia, South Carolina, and North Carolina, 2017—Summary

Abstract

Reliable flood-frequency estimates are an important factor for hydraulic structure design and floodplain management. Annual peak streamflows (hereafter, referred to as peak flows) measured at 965 U.S. Geological Survey (USGS) streamgages were used to compute flood-frequency estimates with annual exceedance probabilities (AEPs) of 50, 20, 10, 4, 2, 1, 0.5, and 0.2 percent. These AEPs correspond to flood-recurrence intervals of 2, 5, 10, 25, 50, 100, 200, and 500 years, respectively. A subset of these streamgages (801) were used to develop equations to predict the flood-frequency estimates (hereafter, referred to as AEP streamflows) at ungaged stream locations. This study was completed by the USGS in cooperation with the Georgia, South Carolina, and North Carolina Departments of Transportation and the North Carolina Department of Crime Control and Public Safety; the results are summarized in this fact sheet. Complete results and the supporting data are presented in the companion scientific investigations report and data release (Feaster and others, 2023; Kolb and others, 2023).