Regional flood skew for parts of the Mid-Atlantic and South-Atlantic-Gulf regions (hydrologic unit codes 02 and 03) in eastern Virginia, eastern West Virginia, and western Maryland

This dataset contains site information, results of at-site flood-frequency analysis, and results of Bayesian weighted least-squares/Bayesian generalized least-squares (B-WLS/B-GLS) analysis of regional skewness of the annual peak flows for 405 streamflow gaging stations (streamgages) operated by the U.S. Geological Survey (USGS) in parts of the Mid-Atlantic and South-Atlantic-Gulf regions (hydrologic unit codes 02 and 03) in eastern Virginia, eastern West Virginia, and western Maryland. With few exceptions, annual peak-flow data through the 2021 water year (A water year is defined as the period October 1-September 30, named for the year in which it ends) were used in the study. For regional skew analysis, 234 of the 405 candidate streamgages were removed for pseudo record lengths (PRL; Veilleux and Wagner, 2021) less than 50 years, 50 were removed for redundancy, and 9 were removed for regulation, urbanization, or being outside the study area (see file "VAskew_Region1.csv" in this dataset). For the remaining 112 of 405 candidate streamgages, B-WLS/B-GLS regression (Veilleux and Wagner, 2021) was used to relate flood skew to a suite of 32 explanatory variables (see file "BasinCharDefinitions.csv"). None of the explanatory variables tested had sufficient predictive power in explaining the variability in skew in the region; thus, a constant model of regional skew, 0.50 (average variance of prediction 0.33, standard error 0.574) was selected for the study area (Messinger and others, 2025). For the 405 candidate streamgages, annual peak-flow data through the 2021 water year ("VAskew_region1.pkf") and specification ("VAskew_region1.psf"), output ("VASKEW_REGION1.PRT"), and export ("VASKEW_REGION1.EXP") files from flood-frequency analysis in version 7.4.1 of USGS PeakFQ software (hereafter referred to as "PeakFQ"; Veilleux and others, 2014; Flynn and others, 2006) are provided. Two .csv files are provided, one describing the basin characteristics tested ("BasinCharsTested.csv") and the other ("VAskew_Region1.csv") containing site information (U.S. Geological Survey, 2023), results of flood-frequency analysis in PeakFQ, and, for the 112 streamgages used in the B-WLS/B-GLS regression, PRL, unbiased at-site skew, the B-WLS/B-GLS residual and metrics of leverage and influence. A geographic information systems (GIS) shapefile (.shp) containing a polygon representing the geographic extent of the study area is also included.