The U.S. Geological Survey (USGS) recently completed a report documenting methods for peak-flow frequency analysis following implementation of the Bulletin 17C guidelines (https://doi.org/10.3133/tm4B5). The methods provide estimates of peak-flow quantiles for 50-, 20-, 10-, 4-, 2-, 1-, 0.5-, and 0.2-percent annual exceedance probabilities (AEPs) for selected streamgages operated by the USGS and Environment Canada. In association with the report, this data release presents peak-flow frequency analyses for 148 streamgages (127 stations in Maine, 16 in New Hampshire, and 5 in New Brunswick, Canada). Included are 148 individual ".PRT" text files that contain results of the flood-frequency analyses of annual peak flows from all of the selected streamgages. The files were generated using version 7.3 of USGS software PeakFQ (https://water.usgs.gov/software/PeakFQ/; Veilleux and others, 2014) to conduct flood-frequency analyses using the expected moments algorithm (England and others, 2018). The peak-flow files used as input to PeakFQ were obtained from the USGS National Water Information System (NWIS) database (https://nwis.waterdata.usgs.gov/usa/nwis/peak) and contained annual peak flows ending in water year 2019. Results of the flood-frequency analyses at streamgages that did not have storage or regulation in the watershed (124 of the total 148) were used to develop peak-flow regression equations for estimating the selected AEPs at ungaged sites in Maine. Results from the unregulated streamgages that had periods of record of at least 20 years (51 of the 124) were used for a Maine skew analysis also outlined in the report. This data release also includes eight Excel tables summarizing the results of the peak-flow frequency analyses and peak-flow regionalization. Tables include basin characteristics used in the regionalization, information needed for flood-frequency analyses including periods of record used in analyses and skew values, maximum instantaneous floods , flood frequency estimates , information needed for advanced accuracy analyses for the streamgages and information needed for calculation of the 90-percent confidence intervals of the peak-flow equations for the AEPs.

The USGS Wyoming-Montana Water Science Center (WY–MT WSC) recently completed a report documenting methods for peak-flow frequency analysis following implementation of the Bulletin 17C guidelines. The methods are used to provide estimates of peak-flow quantiles for 50-, 42.9-, 20-, 10-, 4-, 2-, 1-, 0.5-, and 0.2-percent annual exceedance probabilities (AEPs) for selected streamgages operated by the WY–MT WSC. In association with the report, this data release presents peak-flow frequency analyses for 99 selected streamgages that serve as examples showing various aspects of the WY-MT WSC frequency-analysis methods.

The USGS Wyoming-Montana Water Science Center (WY–MT WSC) recently completed a report documenting methods for peak-flow frequency analysis following implementation of the Bulletin 17C guidelines. The methods are used to provide estimates of peak-flow quantiles for 50-, 42.9-, 20-, 10-, 4-, 2-, 1-, 0.5-, and 0.2-percent annual exceedance probabilities (AEPs) for selected streamgages operated by the WY–MT WSC. In association with the report, this data release presents peak-flow frequency analyses for 99 selected streamgages that serve as examples showing various aspects of the WY-MT WSC frequency-analysis methods.

"NewEngland_pkflows.PRT" is a text file that contains results of flood-frequency analysis of annual peak flows from 186 selected streamflow gaging stations (streamgages) operated by the U.S. Geological Survey (USGS) in the New England region (Maine, Connecticut, Massachusetts, Rhode Island, New York, New Hampshire, and Vermont). Only streamgages in the region that were also in the USGS "GAGES II" database (https://water.usgs.gov/GIS/metadata/usgswrd/XML/gagesII_Sept2011.xml) were considered for use in the study. The file was generated by combining PeakFQ output (.PRT) files created using version 7.0 of USGS software PeakFQ (https://water.usgs.gov/software/PeakFQ/; Veilleux and others, 2014) to conduct flood-frequency analyses using the Expected Moments Algorithm (England and others, 2018). The peak-flow files used as input to PeakFQ were obtained from the USGS National Water Information System (NWIS) database (https://nwis.waterdata.usgs.gov/usa/nwis/peak) and contained annual peak flows ending in water year 2011. Results of the flood-frequency analyses were used to estimate skewness of annual peak flows in the New England region using Bayesian Weighted Least Squares / Bayesian Generalized Least Squares (B-WLS / B-GLS) regression (Veilleux and others, 2019).

"NewEngland_pkflows.txt" contains annual peak-flow data for 186 selected streamflow gaging stations (streamgages) operated by the U.S. Geological Survey (USGS) in the New England region (Maine, Connecticut, Massachusetts, Rhode Island, New York, New Hampshire, and Vermont). Only streamgages in the region that were also in the USGS "GAGES II" database (https://water.usgs.gov/GIS/metadata/usgswrd/XML/gagesII_Sept2011.xml) were considered for use in the study. The annual peak-flow data were obtained from the USGS National Water Information System (NWIS) database (https://nwis.waterdata.usgs.gov/usa/nwis/peak) and contain annual peak flows ending in water year 2011. The annual peak flows were used in version 7.0 of USGS software PeakFQ (https://water.usgs.gov/software/PeakFQ/; Veilleux and others, 2014; Flynn and others, 2006) to conduct flood-frequency analyses using the Expected Moments Algorithm (EMA; England and others, 2018). Data contained in the PeakFQ output (.PRT) files (also included in this data release) were then used to estimate regional skewness of the annual peak flows using Bayesian Weighted Least Squares / Bayesian Generalized Least Squares (B-WLS / B-GLS) regression (Veilleux and others, 2019).

"NewEngland_pkflows.PRT" is a text file that contains results of flood-frequency analysis of annual peak flows from 186 selected streamflow gaging stations (streamgages) operated by the U.S. Geological Survey (USGS) in the New England region (Maine, Connecticut, Massachusetts, Rhode Island, New York, New Hampshire, and Vermont). Only streamgages in the region that were also in the USGS "GAGES II" database (https://water.usgs.gov/GIS/metadata/usgswrd/XML/gagesII_Sept2011.xml) were considered for use in the study. The file was generated by combining PeakFQ output (.PRT) files created using version 7.0 of USGS software PeakFQ (https://water.usgs.gov/software/PeakFQ/; Veilleux and others, 2014) to conduct flood-frequency analyses using the Expected Moments Algorithm (England and others, 2018). The peak-flow files used as input to PeakFQ were obtained from the USGS National Water Information System (NWIS) database (https://nwis.waterdata.usgs.gov/usa/nwis/peak) and contained annual peak flows ending in water year 2011. Results of the flood-frequency analyses were used to estimate skewness of annual peak flows in the New England region using Bayesian Weighted Least Squares / Bayesian Generalized Least Squares (B-WLS / B-GLS) regression (Veilleux and others, 2019).

"NewEngland_pkflows.PRT" is a text file that contains results of flood-frequency analysis of annual peak flows from 186 selected streamflow gaging stations (streamgages) operated by the U.S. Geological Survey (USGS) in the New England region (Maine, Connecticut, Massachusetts, Rhode Island, New York, New Hampshire, and Vermont). Only streamgages in the region that were also in the USGS "GAGES II" database (https://water.usgs.gov/GIS/metadata/usgswrd/XML/gagesII_Sept2011.xml) were considered for use in the study. The file was generated by combining PeakFQ output (.PRT) files created using version 7.0 of USGS software PeakFQ (https://water.usgs.gov/software/PeakFQ/; Veilleux and others, 2014) to conduct flood-frequency analyses using the Expected Moments Algorithm (England and others, 2018). The peak-flow files used as input to PeakFQ were obtained from the USGS National Water Information System (NWIS) database (https://nwis.waterdata.usgs.gov/usa/nwis/peak) and contained annual peak flows ending in water year 2011. Results of the flood-frequency analyses were used to estimate skewness of annual peak flows in the New England region using Bayesian Weighted Least Squares / Bayesian Generalized Least Squares (B-WLS / B-GLS) regression (Veilleux and others, 2019).

"NewEngland_pkflows.txt" contains annual peak-flow data for 186 selected streamflow gaging stations (streamgages) operated by the U.S. Geological Survey (USGS) in the New England region (Maine, Connecticut, Massachusetts, Rhode Island, New York, New Hampshire, and Vermont). Only streamgages in the region that were also in the USGS "GAGES II" database (https://water.usgs.gov/GIS/metadata/usgswrd/XML/gagesII_Sept2011.xml) were considered for use in the study. The annual peak-flow data were obtained from the USGS National Water Information System (NWIS) database (https://nwis.waterdata.usgs.gov/usa/nwis/peak) and contain annual peak flows ending in water year 2011. The annual peak flows were used in version 7.0 of USGS software PeakFQ (https://water.usgs.gov/software/PeakFQ/; Veilleux and others, 2014; Flynn and others, 2006) to conduct flood-frequency analyses using the Expected Moments Algorithm (EMA; England and others, 2018). Data contained in the PeakFQ output (.PRT) files (also included in this data release) were then used to estimate regional skewness of the annual peak flows using Bayesian Weighted Least Squares / Bayesian Generalized Least Squares (B-WLS / B-GLS) regression (Veilleux and others, 2019).

The U.S. Geological Survey (USGS) Central Midwest Water Science Center (CMWSC) completed a report (Over and others, 2023) documenting methods for peak-flow frequency analysis in Illinois following Bulletin 17C guidelines. The methods are used to provide estimates of peak-flow quantiles for 50-, 20-, 10-, 4-, 2-, 1-, 0.5-, and 0.2-percent annual exceedance probabilities (AEPs) for selected USGS streamgages. This data release presents peak-flow frequency analyses for selected streamgages in Illinois, Indiana, and Wisconsin, based on data through water year 2017 (a water year is the period from October 1 to September 30 and is designated by the year in which it ends; for example, water year 2017 was from October 1, 2016, to September 30, 2017). References Cited: England, J.F., Jr., Cohn, T.A., Faber, B.A., Stedinger, J.R., Thomas, W.O., Jr., Veilleux, A.G., Kiang, J.E., and Mason, R.R., Jr., 2019, Guidelines for determining flood flow frequency — Bulletin 17C (ver. 1.1, May 2019): U.S. Geological Survey Techniques and Methods, book 4, chap. B5, 148 p., https://doi.org/10.3133/tm4B5. Over, T.M., Marti, M.K., O'Shea, P.S., Sharpe, J.B., 2023, Estimating peak-flow quantiles for selected annual exceedance probabilities in Illinois (Report No. FHWA-ICT-23-014). Illinois Center for Transportation. https://doi.org/10.36501/0197-9191/23-019.

The U.S. Geological Survey (USGS) Central Midwest Water Science Center (CMWSC) completed a report (Over and others, 2023) documenting methods for peak-flow frequency analysis in Illinois following Bulletin 17C guidelines. The methods are used to provide estimates of peak-flow quantiles for 50-, 20-, 10-, 4-, 2-, 1-, 0.5-, and 0.2-percent annual exceedance probabilities (AEPs) for selected USGS streamgages. This data release presents peak-flow frequency analyses for selected streamgages in Illinois, Indiana, and Wisconsin, based on data through water year 2017 (a water year is the period from October 1 to September 30 and is designated by the year in which it ends; for example, water year 2017 was from October 1, 2016, to September 30, 2017). References Cited: England, J.F., Jr., Cohn, T.A., Faber, B.A., Stedinger, J.R., Thomas, W.O., Jr., Veilleux, A.G., Kiang, J.E., and Mason, R.R., Jr., 2019, Guidelines for determining flood flow frequency — Bulletin 17C (ver. 1.1, May 2019): U.S. Geological Survey Techniques and Methods, book 4, chap. B5, 148 p., https://doi.org/10.3133/tm4B5. Over, T.M., Marti, M.K., O'Shea, P.S., Sharpe, J.B., 2023, Estimating peak-flow quantiles for selected annual exceedance probabilities in Illinois (Report No. FHWA-ICT-23-014). Illinois Center for Transportation. https://doi.org/10.36501/0197-9191/23-019.