At-site flood frequency estimates for 64 urban streamgages in Alabama and Mississippi using data through water year 2024

This dataset contains site information and results of flood frequency analysis for 64 urban streamflow gaging stations (streamgages) operated by the U.S. Geological Survey (USGS) in Alabama and Mississippi. Site information and annual peak-flow data from the 1885 - 2024 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 8.0.0 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 Alabama and Mississippi (Anderson, 2020 and Anderson, 2018, respectively). Site information is provided in .csv format ("AL_MS_UrbanFFreq_SiteInfo.csv"). Peak-flow ("AL_MS_UrbanFFreq_nwis_peak.txt"), specification ("AL_MS_UrbanFFreq.psf"), and output files from PeakFQ ("AL_MS_UrbanFFreq_emp.csv", "AL_MS_UrbanFFreq_lp3.csv", "AL_MS_UrbanFFreq_mgb.csv", "AL_MS_UrbanFFreq_qnt.csv", and "AL_MS_UrbanFFreq_trd.csv") are provided.  Estimates of the 0.5, 0.2, 0.1, 0.04, 0.02, 0.01, 0.005, and 0.002 annual exceedance probabilities (the 2-, 5-, 10-, 25-, 50-, 100-, 200-, and 500-year recurrence intervals, respectively) are in file "AL_MS_UrbanFFreq_qnt.csv".