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.
