Peak-flow frequency analysis for U.S. Geological Survey streamgages in Northwestern Iowa, based on data through water year 2024

This data release presents a peak-flow frequency analysis for U.S. Geological Survey streamgages in northwestern Iowa, following flooding in June 2024. Updated estimates of peak-flow frequency are provided for 33 streamgages. The annual peak-streamflow data used in the frequency analysis were downloaded from the U.S. Geological Survey National Water Information System database (U.S. Geological Survey, 2025) and the procedures used in the peak-flow frequency analyses are described in Eash and others (2013) and in the primary publication (Marti and O'Shea, 2026). The USGS computer program PeakFQ version 7.5.1, was used for these analyses; a description of this program can be found in Flynn and others (2006) and Veilleux and others (2014).

This data release includes four comma-separated values files (.csv):

Table_DR-1_streamgage_info.csv, with the streamgage information for all streamgages used in analysis.

Table_DR-2_analytical_results.csv, with the analytical methods used for peak-flow frequency analysis.

Table_DR-3_peak_flow_frequency_results.csv, with the peak-flow frequency results, including at-site, regional-regression, and weighted estimates.

Table_DR-4_variance.csv, containing the variance of prediction for all estimate types.

It also includes a zip file, "PeakFQ_Data.zip", which contains two folders: (1) PeakFQ_Input and (2) PeakFQ_Output. The "PeakFQ_Input" folder contains the text file containing annual peak streamflow data (ffa_2024_WATSTORE.txt) and the specification file, ffa_2024.psf, containing information used to run PeakFQ. "PeakFQ_Output" folder includes a FFA_2024.PRT file and a FFA_2024.EXP file that contain tabular output from PeakFQ. More information on input and output data file formats are described in the PeakFQ user's manual (Flynn and others, 2006).