The U.S. Geological Survey (USGS) has a long history of working cooperatively with the South Carolina Department of Transportation to develop methods for estimating the magnitude and frequency of floods for rural and urban basins that have minimal to no regulation or tidal influence. As part of those previous investigations, flood-frequency estimates have been generated at selected regulated streamgages. This is the data release for the report which assesses the effects of impoundments on flood-frequency characteristics by comparing annual exceedance probability (AEP) streamflows from pre- and post-regulated (before and after impoundment) periods at 18 USGS long-term streamgages, which is defined as a streamgage with 30 or more years of record, in Georgia, South Carolina, and North Carolina. For an assessment of how differences in such statistics can be influenced by period of record and hydrologic conditions captured in those records, which could be considered as natural variability, AEP streamflows at an additional 18 long-term USGS streamgages that represent unregulated conditions in those three states were computed and compared for the first and last half of those records. This data release contains the tables and software input and output files from the report Effects of impoundments on selected flood-frequency and daily mean streamflow characteristics in Georgia, South Carolina, and North Carolina (Feaster and Musser, 2023). These tables contain information about the streamgages used in the analysis. The tables are contained in the zip file Impoundments_tables.zip, which includes 8 tab-delimited txt files, and a formatted Excel file of all the tables used in the publication. Two additional files, PeakFQ_files.zip and WREG-Archive.zip include input and output files from the analysis.

Reliable estimates of the magnitude and frequency of floods are an important part of the framework for hydraulic-structure design and flood-plain management. Annual peak flows measured at U.S. Geological Survey streamgages are used to compute flood-frequency estimates at those streamgages. However, flood-frequency estimates also are needed at ungaged stream locations. A process known as regionalization was used to develop regression equations to estimate the magnitude and frequency of floods at ungaged locations. This dataset contains the supporting tables and updated hydrologic region boundaries used in the 2017 flood-frequency study for Georgia, South Carolina, and North Carolina.

Reliable estimates of the magnitude and frequency of floods are an important part of the framework for hydraulic-structure design and flood-plain management in Georgia, South Carolina, and North Carolina (study area). Annual peak flows measured at U.S. Geological Survey streamgages were used to compute at-site flood-frequency estimates at those streamgages in the study area based on annual peak-flows records through 2017. Flood-frequency estimates also are needed at ungaged stream locations. A process known as regionalization was used to develop regression equations to estimate the magnitude and frequency of floods at ungaged locations. This model archive provides the inputs and outputs for (1) the at-site flood-frequency statistics and (2) the regression models developed to allow for estimation of flood-frequency statistics at ungaged stream locations in the study area. The inputs and outputs for the at-site flood-frequency statistics are provided under the SAWSC PeakFQ input and output files for at-site flood-frequency statistics child item. The inputs and outputs for the regression models are provided under the SAWSC rural flood-frequency regression models (R scripts and applications) child item. Further details concerning the inputs and outputs are provided within the metadata and ReadMe files underneath each child item within this data release. Information describing the contents of this model archive is provided below in a text-based file attached to the front landing page for this data release.

Reliable estimates of the magnitude and frequency of floods are an important part of the framework for hydraulic-structure design and flood-plain management in Georgia, South Carolina, and North Carolina (study area). Annual peak flows measured at U.S. Geological Survey streamgages were used to compute at-site flood-frequency estimates at those streamgages in the study area based on annual peak-flows records through 2017. Flood-frequency estimates also are needed at ungaged stream locations. A process known as regionalization was used to develop regression equations to estimate the magnitude and frequency of floods at ungaged locations. This model archive provides the inputs and outputs for (1) the at-site flood-frequency statistics and (2) the regression models developed to allow for estimation of flood-frequency statistics at ungaged stream locations in the study area. The inputs and outputs for the at-site flood-frequency statistics are provided under the SAWSC PeakFQ input and output files for at-site flood-frequency statistics child item. The inputs and outputs for the regression models are provided under the SAWSC rural flood-frequency regression models (R scripts and applications) child item. Further details concerning the inputs and outputs are provided within the metadata and ReadMe files underneath each child item within this data release. Information describing the contents of this model archive is provided below in a text-based file attached to the front landing page for this data release.

This dataset contains site information and results of flood-frequency analysis for 139 urban streamflow gaging stations (streamgages) operated by the U.S. Geological Survey (USGS) in Tennessee and parts of Alabama, Georgia, Mississippi, North Carolina, and South Carolina. Developed imperviousness in the basins, based on the 2011 National Land Cover Database, was at least 10 percent (Homer and others, 2015). Drainage areas of the streamgage basins ranged from 0.15 - 161 square miles. Annual peak-flow data from the 1947 - 2022 water years were used in the study (U.S. Geological Survey, 2024). Peak-flow (.pkf), specification (.psf), output (.PRT), and export (.EXP) files from flood-frequency analysis in USGS PeakFQ software (Veilleux and others, 2014; Flynn and others, 2006) are provided. Site information and results of flood-frequency analysis are provided in .csv format.

This dataset contains site information and results of flood-frequency analysis for 139 urban streamflow gaging stations (streamgages) operated by the U.S. Geological Survey (USGS) in Tennessee and parts of Alabama, Georgia, Mississippi, North Carolina, and South Carolina. Developed imperviousness in the basins, based on the 2011 National Land Cover Database, was at least 10 percent (Homer and others, 2015). Drainage areas of the streamgage basins ranged from 0.15 - 161 square miles. Annual peak-flow data from the 1947 - 2022 water years were used in the study (U.S. Geological Survey, 2024). Peak-flow (.pkf), specification (.psf), output (.PRT), and export (.EXP) files from flood-frequency analysis in USGS PeakFQ software (Veilleux and others, 2014; Flynn and others, 2006) are provided. Site information and results of flood-frequency analysis are provided in .csv format.

In cooperation with the South Carolina Department of Transportation (SCDOT), the U.S. Geological Survey prepared geospatial layers illustrating the boundaries of the regions used in the South Carolina (SC) Stream Hydrograph Methods presented in Bohman (1990, 1992). The region limits were described in written text and depicted in figures in Bohman (1990,1992), but have not been provided as geospatial layers (due to the age of the original publications). This project used best-available geospatial data from the U.S. Environmental Protection Agency (USEPA) ecoregions (2013) to create equivalent geospatial representations of the Bohman (1990, 1992) region boundaries for the SC Stream Hydrograph Methods. These layers will be used in the SC StreamStats application to generate hydrographs for estimated storm runoff simulations. The StreamStats application (https://streamstats.usgs.gov) provides access to spatial analytical tools that are useful for water-resources planning and management, and for engineering and design purposes. The map-based user interface can be used to delineate watershed areas, retrieve basin characteristics, estimates of flow statistics, and more.

This dataset contains an inventory of South Carolina U.S. Geological Survey (USGS) streamgages evaluated in 2017 as part of gage network gap assessment. Both continuous record and crest stage gages are included in this dataset. The data are grouped into three categories: rural streamgages with equal to or greater than 10 years of peak-flow data, rural streamgages with less than 10 years of peak-flow data, and urban streamgages.

This dataset contains an inventory of South Carolina U.S. Geological Survey (USGS) streamgages evaluated in 2017 as part of gage network gap assessment. Both continuous record and crest stage gages are included in this dataset. The data are grouped into three categories: rural streamgages with equal to or greater than 10 years of peak-flow data, rural streamgages with less than 10 years of peak-flow data, and urban streamgages.

This dataset contains site information and results of flood frequency analysis for 64 urban streamflow gaging stations (streamgages) operated by the U.S. Geological Survey (USGS) in Alabama and Mississippi. Site information and annual peak-flow data from the 1885 - 2024 water years were obtained from the USGS National Water Information System (NWIS) database (U.S. Geological Survey, 2025). Flood frequency analysis was conducted in version 8.0.0 of USGS PeakFQ software (Siefken and others, 2024) in the R environment (R Core Team, 2024) following the guidelines set forth in Bulletin 17C (England and others, 2018) and using the approaches described in the most recent flood frequency reports for Alabama and Mississippi (Anderson, 2020 and Anderson, 2018, respectively). Site information is provided in .csv format ("AL_MS_UrbanFFreq_SiteInfo.csv"). Peak-flow ("AL_MS_UrbanFFreq_nwis_peak.txt"), specification ("AL_MS_UrbanFFreq.psf"), and output files from PeakFQ ("AL_MS_UrbanFFreq_emp.csv", "AL_MS_UrbanFFreq_lp3.csv", "AL_MS_UrbanFFreq_mgb.csv", "AL_MS_UrbanFFreq_qnt.csv", and "AL_MS_UrbanFFreq_trd.csv") are provided. Estimates of the 0.5, 0.2, 0.1, 0.04, 0.02, 0.01, 0.005, and 0.002 annual exceedance probabilities (the 2-, 5-, 10-, 25-, 50-, 100-, 200-, and 500-year recurrence intervals, respectively) are in file "AL_MS_UrbanFFreq_qnt.csv".