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Water Resources of the United States

Summary of NFF


NFF - The National Flood Frequency Program


Estimates of the magnitude and frequency of flood-peak discharges and flood hydrographs are used for a variety of purposes, such as the design of bridges, culverts, and flood-control structures, and for the management and regulation of flood plains. These estimates are often needed at ungaged sites where no observed flood data are available.

To provide simple methods of estimating flood-peak discharges, the U.S. Geological Survey (USGS) has developed and published regression equations for every State, the Commonwealth of Puerto Rico, and a number of metropolitan areas in the United States. These equations have been compiled into the National Flood Frequency (NFF) Program.


NFF is a Visual Basic program that can be used to:

Note: References to commercial vendors of software products or services is for informational purposes only and does not imply endorsement by the U.S. Government.


NFF works in concert with a Microsoft Access database, NFFv3.mdb, which contains the information needed to solve the regression equations for each State. As new equations become available, the NFF database will be updated and links to new documentation will be provided from the NFF web site. Users should check often to determine if the database has been updated with new equations for their areas of interest.


Version history can be obtained at


NFF requires user input of physical and climatic characteristics used as independent variables in the equations. Manual or automated methods for measuring the input parameters are described in documentation provided for each state.


Output is provided in the NFF user interface, and includes input parameters, peak-flow estimates, standard errors, and equivalent years of record. This output can be saved to a text file or printed. Hydrographs and frequency plots are presented in separate windows. The graphs and data used to create them can be saved to bitmap files or printed.


NFF requires a computer running Windows 98 (or newer) or Windows NT Version 4.0 with service pack 5 (or higher). Adobe Acrobat Reader is required to display or print the User Manual in PDF format; however, the User Manual is available in other formats in addition to PDF. Microsoft Internet Explorer version 5.0 or newer is required to invoke the on-line help section. The amount of free disk space that is required varies greatly depending on the amount of station data stored in database files. For optimal performance, a processor running at 400 megahertz or faster with at least 128 megabytes of memory is recommended.


Documentation of the program history, content, theory, and application, including a users manual, is contained in:


Inquiries about this software should be directed to:

U.S. Geological Survey
Office of Surface Water
Kernell Ries
12201 Sunrise Valley Dr., MS 415
Reston, VA 20192
Electronic mail:
Fax: 703-648-5722
Phone: 703-648-5307

NFF page

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