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In Reply Refer To:
Mail Stop 415

November 21, 2002

OFFICE OF SURFACE WATER MEMORANDUM

SUBJECT: Availability of the National Flood Frequency (NFF) program, version 3, and accompanying documentation

The purpose of this memorandum is to announce the availability of the National Flood Frequency (NFF) program, version 3, and accompanying documentation. This PC program represents a compilation of the current USGS regression equations that can be used to estimate the magnitude and frequency of flood-peak discharges for rural and urban ungaged sites in the 50 States, Puerto Rico, and the Island of Tutuila, American Samoa. The report and program should be of interest to those individuals involved in flood-frequency analysis.

The NFF program includes over 2,000 regression equations in 289 flood regions throughout the country. Procedures for estimating flood hydrographs for selected recurrence-interval peak discharges are also available in NFF. The program is documented in

Ries, K.G., III, and Crouse, M. Y., 2002, The National Flood Frequency Program, Version 3: A computer program for estimating magnitude and frequency of floods for ungaged sites: U.S. Geological Survey Water-Resources Investigations Report 02-4168, 41 p.,

and in

Perl, C.D., and Ries, K.G., III, 2002, Using the National Flood Frequency Program, Version 3: A computer program for estimating magnitude and frequency of floods for ungaged sites, U.S. Geological Survey Fact Sheet 084-02, 4 p.

The software, an accompanying Access data base (NFFv3.mdb), the WRIR and the Fact Sheet can be downloaded from the Web at http://water.usgs.gov/software/nff.html or by anonymous FTP at water.usgs.gov (directory /pub/software/surface_water/nff). The web page also contains links to documentation for solving the regression equations for individual States.

The USGS plans to update NFF data base quickly when new regression equations are published in various States; therefore, NFF users should check the Web site often to assure that they have the latest version of the data base. There are plans for release of NFF version 4 within a year that will include the ability to estimate peak flows for ungaged sites by use of the region-of-influence regression method and other enhancements.

Problems with the NFF program, suggestions for improving the program, questions about the hydrologic procedures or requests for additional information can be addressed to Kernell Ries, of the Office of Surface Water, at 703-648-5307 or kries@usgs.gov.

/signed/

J. Michael Norris
Acting Chief, Office of Surface Water


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