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Water Resources of the United States


Flood Frequency Analysis Based on Bulletin 17B and recommendations of the Advisory Committee on Water Information (ACWI) Subcommittee on Hydrology (SOH) Hydrologic Frequency Analysis Work Group (HFAWG)

Program PeakFQ implements both the Bulletin 17B and Expected Moments Algorithm (EMA) procedures for flood-frequency analysis of streamflow records, providing estimates of flood magnitudes and their corresponding variance for a range of 15 annual exceedance probabilities, including 0.6667, 0.50, 0.4292 0.20, 0.10, 0.04, 0.02, 0.01, 0.005, and 0.002 (recurrence intervals 1.5, 2, 2.33, 5, 10, 25, 50, 100, 200, and 500 years, respectively.) The output also includes estimates of the parameters of the log-Pearson Type III frequency distribution, including the logarithmic mean, standard deviation, skew, and mean square error of the skew. The output graph includes the fitted frequency curve, systematic peaks, low outliers, censored peaks, interval peaks, historic peaks, thresholds, and confidence limits.

PeakFQ reads annual peaks in the standard peakfq (WATSTORE) text format available from NWISWeb (

Current Version: 7.1
Release Date: March 14, 2014
Version History ( release.pdf)
Frequently Asked Questions ( FAQ)
Veilleux, A.G., Cohn, T.A., Flynn, K.M., Mason, R.R., Jr., and Hummel, P.R., 2014, Estimating magnitude and frequency of floods using the PeakFQ 7.0 program: U.S. Geological Survey Fact Sheet 2013-3108, 2 p.,
Flynn, K.M., Kirby, W.H., and Hummel, P.R., 2006, User's manual for program PeakFQ, Annual Flood Frequency Analysis Using Bulletin 17B Guidelines: U.S. Geological Survey Techniques and Methods Book 4, Chapter B4, 42 pgs.
[ On-line | PDF | chm ]
Interagency Advisory Committee on Water Data, 1982, Guidelines for determining flood-flow frequency: Bulletin 17B of the Hydrology Subcommittee, Office of Water Data Coordination, U.S. Geological Survey, Reston,Va., 183 p.,
Software User Rights Notice
NOTE: Electronic and/or print versions of many U.S. Geological Survey reports can be found at the Publications Warehouse (
Contact: U.S.Geological Survey
Office of Surface Water
415 National Center
Reston, VA 20192

Distribution Files


Operating System

Download File




Windows 7/8

readme.txt Installation and usage information
PeakFQ_7.1.exe Self-installing executable, includes executable program, sample data, and documentation Source code

The following software distributions have been superseded and are replaced by the newer version above.
These versions are provided online for historical reference only.
There is no support for installation or use of these versions.



Windows XP

README.TXT and PKFQWin_5.2.exe




README.TXT and peakfq4_1.exe (2.51MB)

Sun Solaris

README.TXT and peakfq4.1.Solaris.tar.gz (1.3MB)


README.TXT and peakfq4.1.source.tar.gz (705K)

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