Data in support of the Washington D.C. StreamStats project in Washington D.C. and parts of Delaware, Maryland, New Jersey, Pennsylvania, and Virginia (ver. 2.0, February 2026)

These datasets in this release contain information and results for the Washington D.C. StreamStats project in Washington D.C. and parts of Delaware, Maryland, New Jersey, Pennsylvania, and Virginia. These datasets were created to support the Washington D.C. StreamStats project funded by the Washington D.C. Department of Energy and Environment (DOEE):

Digital elevation model (DEM), flow direction and catchment layers were conditioned using Washington's D.C.’s stormwater network layer. The data are hosted online as a component of the USGS StreamStats web application (U.S. Geological Survey, 2019; refer also to https://streamstats.usgs.gov), where users can interact with a map of Washington D.C.’s stormwater pipe system and the National Hydrography Dataset to delineate drainage basins that account for pipe flow.

Basin characteristics were generated for 154 urban streamflow gaging stations (streamgages) operated by the U.S. Geological Survey (USGS) in the study area (Kline and others, 2025a). Characteristics included the mean basin slope (percent rise) using 3-meter and 10-foot resolution digital elevation models (DEM) and percent developed imperviousness cover derived from 1-meter resolution land cover datasets (CBP, 2023; UVM, 2016).

Flood frequency analyses were completed for 154 urban streamgages in the study area (Kline and others, 2025b). Site information and annual peak-flow data from the 1924 - 2022 water years were obtained from the USGS National Water Information System (NWIS) database (U.S. Geological Survey, 2025). Flood frequency analysis was conducted in version 8.1.0 of USGS PeakFQ software (Siefken and others, 2024) in the R environment (R Core Team, 2024) following the guidelines set forth in Bulletin 17C (England and others, 2018) and using the approaches described in the most recent flood frequency reports for Pennsylvania and North Carolina (Roland and Stuckey, 2019; Feaster and others, 2023).

GLS regression was used to relate drainage area, basin slope, and percent of impervious cover (from basin characteristics data release) 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, 2026). GLS regression was conducted using Version 3.0 of USGS Weighted Regression (WREG) software (Farmer and others, 2021; Eng and others, 2009). 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.