Annual peak-flow data and results of flood-frequency analyses for 76 selected streamflow gaging stations operated by the U.S. Geological Survey in the upper White River Basin, Missouri and Arkansas, computed using an updated generalized flood skew

This dataset contains site information, basin characteristics, results of flood-frequency analysis, and a generalized (regional) flood skew for 76 selected streamgages operated by the U.S. Geological Survey (USGS) in the upper White River basin (4-digit hydrologic unit 1101) in southern Missouri and northern Arkansas. The Little Rock District U.S. Army Corps of Engineers (USACE) needed updated estimates of streamflows corresponding to selected annual exceedance probabilities (AEPs) and a basin-specific regional flood skew. USGS selected 111 candidate streamgages in the study area that had 20 or more years of gaged annual peak-flow data available through the 2020 water year. After screening for regulation, urbanization, redundant/nested basins, drainage areas greater than 2,500 square miles, and streamgage basins located in the Mississippi Alluvial Plain (8-digit hydrologic unit 11010013), 77 candidate streamgages remained. After conducting the initial flood-frequency analysis to generate at-site (station) skew and its mean squared error (MSE) for development of the regional flood skew, four streamgages with less than 20 years of pseudo effective record length (PRL) and two streamgages with an excessive amount of censored annual peak flows were removed, leaving 71 streamgages (44 in Arkansas and 27 in Missouri) for use in the study. Flood-frequency analysis was done using the Expected Moments Algorithm (EMA) in version 7.3 of USGS software PeakFQ (Veilleux and others, 2014; England and others, 2019). Ten basin characteristics were tested as explanatory variables in a generalized additive model (GAM) of flood skew, but a lack of statistical significance of the variables, including two-dimensional smooths of the locations of the streamgages and the centroids of their basins, indicated that a weighted mean flood skew of -0.132, with a mean squared error of 0.160 and standard error of 0.400, was appropriate. The regional flood skew agrees well with regional flood skew previously developed for Arkansas and Louisiana(skew -0.17, MSE 0.12) using Bayesian generalized least-squares (B-GLS) regression and most of the streamgages in this study (Wagner and others, 2016, appendix 1). The regional flood skew was incorporated in a final flood-frequency analysis in PeakFQ software using a weighted skew (England and others, 2019). In addition to the 71 streamgages used to develop the regional flood skew, five active streamgages that were screened for redundancy (four in Missouri and one in Arkansas) were included in the final flood-frequency analysis. The final estimates of streamflows corresponding to the selected AEPs (0.5, 0.2, 0.1, 0.04, 0.02, 0.01, and 0.002) were weighted with estimates of the same AEPs computed using regional regression equations (Southard and Veilleux, 2014; Wagner and others, 2016) to generate the final weighted estimates, their variances, and 95-percent confidence intervals. References: 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. Southard, R.E., and Veilleux, A.G., 2014, Methods for estimating annual exceedance-probability discharges and largest recorded floods for unregulated streams in rural Missouri: U.S. Geological Survey Scientific Investigations Report 2014-5165, 39 p., http://dx.doi.org/10.3133/sir20145165. 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://doi.org/10.3133/fs20133108 Wagner, D.M., Krieger, J.D., and Veilleux, A.G., 2016, Methods for estimating annual exceedance probability discharges for streams in Arkansas, based on data through water year 2013: U.S. Geological Survey Scientific Investigations Report 2016-5081, 136 p., http://dx.doi.org/10.3133/sir20165081.