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.