This dataset contains results of generalized least-squares (GLS) regression for 63 streamflow gaging stations (streamgages) operated by the U.S. Geological Survey (USGS) on urban streams in Washington D.C. and parts of Delaware, Maryland, New Jersey, Pennsylvania, and Virginia. This dataset was created to support the Washington D.C. StreamStats project funded by the Washington D.C. Department of Energy and Environment (DOEE). GLS regression was used to relate drainage area, basin slope, and percent of impervious cover (Kline and others, 2025b) to previously published estimates of streamflows corresponding to the 0.5, 0.2, 0.1, 0.04, 0.02, 0.01, 0.005, and 0.002 annual exceedance probabilities (AEPs; Kline and others, 2025a). From this regression, equations were developed that can be used to predict streamflows corresponding to the eight selected AEPs at ungaged locations on urban streams (percent developed imperviousness greater than 10%; Homer and others, 2015) in the study area. Standard errors of prediction ranged from 46.1 percent for the 0.2 AEP (the 5-year flood) to 55.0 percent for the 0.002 AEP (the 500-year flood). GLS regression was conducted using version 3.0 of USGS weighted regression (WREG) software (Farmer, 2019; Eng and others, 2009).The input and output files from GLS regression in WREG are located within the "WREG_input.zip" folder. The input files are a text file of basin characteristics for all 63 selected streamgages in the study area ("DC_WREG_SiteInfo.txt") and the peak-flow ("DCStreamStats_FFreq.pkf") and specification ("DCStreamStats_FFreq.psf") files from at-site flood-frequency analysis in version 8.1.0 of USGS PeakFQ software. The following WREG output files are located in the "GLS_output" directory in sub-directories by AEP: "coef.txt," "CoVarMat.txt," "FitandResid.txt," "modelInput.txt," "outputRaw.rda," "PerformanceMetrics.txt," "ResLevInf.txt," and "Weighting.txt". USGS site information, values of the basin characteristics, WLS estimates of streamflows corresponding to the selected AEPs and their variances, and the residual from GLS regression are in file "GLS_Results.csv". The regression equations for each AEP and their associated performance metrics are in file "RegressionEquations.csv".
