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".

This dataset contains site information and results of flood-frequency analysis for 422 streamflow gaging stations (streamgages) operated by the U.S. Geological Survey (USGS) in parts of the Upper Mississippi and Souris-Red-Rainy basins and surrounding areas in the United States. Annual peak-flow data from the 1844 - 2013 water years were used in the study (U.S. Geological Survey, 2024). Following federal guidelines for flood-frequency analysis (Bulletin 17C; England and others, 2018) and methods outlined in recent flood-frequency reports for the region (Eash and others, 2013; Southard and Veilleux, 2014; Levin and Sanocki, 2023; Sanocki and Levin, 2023), the Expected Moments Algorithm (EMA) was used in version 7.5.1 of USGS PeakFQ software (Veilleux and others, 2014; Flynn and others, 2006; https://water.ugsgs.gov/software/PeakFQ/) to conduct the analyses. Results of the analyses, specifically the at-site skew and its mean squared error, are intended for use in Bayesian weighted least-squares/Bayesian generalized least-squares (B-WLS/B-GLS) regression (Veilleux and Wagner, 2019; Veilleux and Wagner, 2021) to model regional skew for the study area. Peak-flow (.pkf), specification (.psf), output (.PRT), and export (.EXP) files from PeakFQ and a .csv file containing site information and selected results of flood-frequency analyses are provided.

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. 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.

This child item contains input files and output files for 857 rural, unregulated streamgages in and near Virginia and West Virginia processed using PeakFQ v7.5.1 for the 2025 flood frequency analysis. Additionally, results were extracted from the input and output files for in each streamgage and summaries were generated. This dataset includes: 1) "Station.zip": A subdirectory containing published annual peaks in WATSTORE format (*.pkf), specifications used for processing in Program Specification File format (*.psf), the output text file containing computation results (*.prt), and the export text file (*exp). The files within these subfolders are aggregated by 2-digit downstream order part number (01, 02, and 03) due to the limitations of maximum number of records PeakFQ v7.5.1 can process at once. At-station skew was used to compute these results. 2) "Weighted.zip": A subdirectory containing published annual peaks in WATSTORE format (*.pkf), specifications used for processing in Program Specification File format (*.psf), the output text file containing computation results (*.prt), and the export text file (*exp). The files within these subfolders are aggregated by 2-digit downstream order part number (01, 02, and 03) due to the limitations of maximum number of records PeakFQ v7.5.1 can process at once. Weighted regional skew was used to compute these results. 3) Table_3_Unregulated_Frequency_Specs.txt: Contains a summary of the specifications and statistics for at-station frequency analyses for 857 streamgages on unregulated streams in and near Virginia and West Virginia for annual peak streamflows including period of record, record length, skew specifications, thresholds and counts of PILFs, value, significance, and slope of the Mann-Kendall trend test; mean, median, and station skew for annual peak streamflows analyzed; regional skew; and MSE of station and regional skew. 4) Table_4_Unregulated_Frequency_Summary.txt: Contains a summary of the results of valid at-station frequency analyses for 813 streamgages on unregulated streams in and near Virginia and West Virginia for annual peak streamflows including flow and variance values for the 0.995, 0.667, 0.5, 0.2, 0.1, 0.04, 0.02, 0.01, 0.005, and 0.002 annual exceedance probabilities.A combination of at-station skew and weighted regional skew was used were appropriate to compute these results.

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.

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.

Flood-frequency analyses were conducted for three streamgages operated by the U.S. Geological Survey (USGS) in the Black River basin of southeastern Missouri (MO) and northeastern Arkansas (AR): 07064000, Black River near Corning, AR; 07068000, Current River at Doniphan, MO; and 07069000, Black River at Pocahontas, AR. Results from the analyses will be used for design purposes by the Arkansas Department of Transportation in the future Interstate 57 alignment from Walnut Ridge, AR to the MO state line. Annual peak-flow data through the 2023 water year (a water year is defined as the period October 1 - September 30, named for the year in which it ends) were downloaded from the USGS National Water Information System (NWIS) website at https://nwis.waterdata.usgs.gov/nwis/peak. Flood-frequency analyses using the Expected Moments Algorithm (EMA) were conducted in version 7.5.1 of USGS PeakFQ software (Veilleux and others, 2014; Flynn and others, 2006) following federal guidelines (England and others, 2019) and the techniques outlined in the most recent USGS flood-frequency report for Arkansas (Wagner and others, 2016). Peak-flow (.pkf), specification (.psf), output (.PRT) and export (.EXP) files from PeakFQ are provided, in addition to a plot of the frequency curve for each streamgage in .PNG format. Results from the flood-frequency analyses, including estimates of the magnitudes of floods corresponding to the 0.5, 0.2, 0.1, 0.04, 0.02, 0.01, 0.005, and 0.002 annual exceedance probabilities (AEPs; the equivalent of the 2-, 5-, 10-, 25-, 50-, 100-, 200-, and 500-year recurrence intervals, respectively) and their associated variances and confidence intervals were retrieved from the .PRT file and are provided in .csv format.

Flood-frequency analyses were conducted for three streamgages operated by the U.S. Geological Survey (USGS) in the Black River basin of southeastern Missouri (MO) and northeastern Arkansas (AR): 07064000, Black River near Corning, AR; 07068000, Current River at Doniphan, MO; and 07069000, Black River at Pocahontas, AR. Results from the analyses will be used for design purposes by the Arkansas Department of Transportation in the future Interstate 57 alignment from Walnut Ridge, AR to the MO state line. Annual peak-flow data through the 2023 water year (a water year is defined as the period October 1 - September 30, named for the year in which it ends) were downloaded from the USGS National Water Information System (NWIS) website at https://nwis.waterdata.usgs.gov/nwis/peak. Flood-frequency analyses using the Expected Moments Algorithm (EMA) were conducted in version 7.5.1 of USGS PeakFQ software (Veilleux and others, 2014; Flynn and others, 2006) following federal guidelines (England and others, 2019) and the techniques outlined in the most recent USGS flood-frequency report for Arkansas (Wagner and others, 2016). Peak-flow (.pkf), specification (.psf), output (.PRT) and export (.EXP) files from PeakFQ are provided, in addition to a plot of the frequency curve for each streamgage in .PNG format. Results from the flood-frequency analyses, including estimates of the magnitudes of floods corresponding to the 0.5, 0.2, 0.1, 0.04, 0.02, 0.01, 0.005, and 0.002 annual exceedance probabilities (AEPs; the equivalent of the 2-, 5-, 10-, 25-, 50-, 100-, 200-, and 500-year recurrence intervals, respectively) and their associated variances and confidence intervals were retrieved from the .PRT file and are provided in .csv format.