Peak-flow frequency analysis for seven selected U.S. Geological Survey streamgages in the Floyd and Little Sioux River Basins, Iowa, based on data through water year 2019

This data release presents peak-flow frequency analyses by the U.S. Geological Survey based on methods described by Eash and others (2013) for streamgages 06600100, Floyd River at Alton, Iowa; 06600300, West Branch Floyd River near Struble, Iowa; 06600500, Floyd River near James, Iowa; 06605000, Ocheyedan River near Spencer, Iowa; 06605850, Little Sioux River at Linn Grove, Iowa; 06607200, Maple River at Mapleton, Iowa; and 06607500, Little Sioux River near Turin, Iowa. These 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). Annual peak-flow data used in the peak-flow frequency analyses for these streamgages were retrieved from the U.S. Geological Survey National Water Information System webpage (U.S. Geological Survey, 2020) and used with USGS flood-frequency analysis software PeakFQ (Veilleux and others, 2014). This data release contains annual peak-flow data (floyd_ffa_2019_WATSTORE.txt), PeakFQ specifications (floyd_ffa_2019.psf), and a series of tables describing the methods and results of the peak-flow frequency analysis (floyd_ffa_2019.xlsx). References Cited: Eash, D.A., Barnes, K.K., and Veilleux, A.G., 2013, Methods for estimating annual exceedance-probability discharges for streams in Iowa, based on data through water year 2010: U.S. Geological Survey Scientific Investigations Report 2013-5086, 63 p. with appendix., http://pubs.usgs.gov/sir/2013/5086/. U.S. Geological Survey, 2020, USGS water data for the Nation: U.S. Geological Survey National Water Information System database, accessed June 25, 2020, at https://doi.org/10.5066/F7P55KJN. Veilleux, A.G., Cohn, T.A., Flynn, K.M., Mason, R.R., Jr., and Hummel, P.R., 2014, Estimating magnitude and frequency of floods using the PeakFQ 7.0 program: U.S. Geological Survey Fact Sheet 2013–3108, 2 p., https://dx.doi.org/10.3133/fs20133108.