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Water Resources of the United States


National Flood Frequency program

Version History

NFF switchover to NSS- 2008/08 - National Flood Frequency Program (NFF) has been replaced by the National Streamflow Statistics Program (NSS). Regional flood frequency equations in NFF are no longer actively updated by USGS staff.

Version 3.2 - 2004/12/14 - Updated the database to NFFv3.2_2004-12-14.mdb. Added new peak-flow equations for Connecticut and Kentucky. Corrected an error in the units displayed for conveyance in the Houston urban equations from in/hr to cubic feet per second. Corrected an error in the Wisconsin Area 1 equation for the 5-year recurrence interval.

Version 3.2 - 2004/09/29 - Updated the database to NFFv3.2_2004-09-29.mdb. This database contains new peak-flow equations for Alaska, Idaho, Ohio, Tennessee, Vermont, Wisconsin, and Wyoming. Along with the new database comes the ability to display 90-percent prediction intervals with the estimates for some of the updated States.

Version 3.2 – 2003/04/30 - Fixed a bug in the weighting routine that occurred when equivalent years of record were missing for the regression estimates, and a bug that occurred when the drainage area for an ungaged site was in more than one region and the regions had different sets of return intervals.

Version 3.1.1 - 2003/03/28 - Fixed a bug in the weighting routine that was introduced in the version 3.1 update.

Version 3.1 - 2003/02/27 - Fixed a problem with solving the national urban equations that occurred when one or more of the local rural equations were missing for the region of interest. If a rural equation, such as the 5-year flow, was missing NFF would use the flow estimate for the next available recurrence interval, such as the 10-year flow, to estimate the urban flow for the missing recurrence interval. All estimates for higher recurrence intervals would also be incorrect.

Version 3.0 - 2002/10/15 - Major change in converting user interface from Microsoft DOS to Microsoft Windows and converting data base from a binary file to Microsoft Access (Note: Use of trade or product names is for identification purposes only and does not constitute endorsement by the U.S. Geological Survey). Updates or corrections to equations for

Version 2.0 - 1996/09/15 - A non-USGS release that added conversions between English and metric units.

Version 1.4 - 1996/09/30 - NFF data base updated to amend incorrect values for:

Version 1.3 - 1996/02/14 - Corrected labeling of flood-frequency recurrence intervals for North Dakota. The equations developed for North Dakota are for the 2-, 10-, 15-, 25-, 50-, 100-, and 500-year recurrence intervals rather than the standard 2-, 5-, 10-, 25-, 50-, 100-, and 500-year intervals.

Version 1.2 - 1995/06/02 - NFF data base updated to amend incorrect exponents in West Virginia's Region 6 equations for the 2-year and 10-year recurrence interval.

Version 1.1 - 1994/11/21 - Initial release.

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