Request for review of National Flood Frequency Program, Version 3 software

In Reply Refer To: 
Mail Stop 415 

February 6, 2002 


Subject:  Request for review of National Flood Frequency Program, Version 3 software 

The Office of Surface Water (OSW) is pleased to announce the availability 
of a beta version of the long-awaited revision to the National Flood 
Frequency Program (NFF). The NFF solves regional peak-flow frequency 
regression equations for every State in the Nation. The OSW has tested the 
basic functionality of the new NFF, but we have limited staff to test 
whether all 2,065 equations for 289 hydrologic regions give correct 
results. Because of this, we are requesting help from the Districts to 
check the accuracy of the equations. Specifically, we request that each 
District assign staff to install the new version of NFF and test the 
equations for each hydrologic region within your area of responsibility 
against regression estimates determined for the gaging stations used in 
the original regression analyses to determine your equations. 

The original version of NFF was released in 1994. Since then, the 
peak-flow equations have been revised for 34 States and American Samoa. 
The NFF web site (/osw/programs/nffp.html) provides a 
table that lists the States with new equations, the associated report 
numbers, and whether or not a fact sheet has been prepared to describe the 
new equations. Links are provided to on-line versions of the reports, when 
available. The fact sheets will be downloadable from the web page when NFF 
is released to the public. 

The new version of NFF incorporates the new equations, and adds the 
ability to weight regression equation-based estimates for an ungaged site 
with estimates obtained by applying the flow per unit area for an upstream 
or downstream gaging station to the drainage area of the ungaged site (the 
drainage-area ratio method). Other major changes to NFF include a new 
Windows graphical user interface (GUI), which replaces the original DOS 
interface, and a Microsoft Access data base, which replaces the original 
NFF-specific binary database. This Access data base will be shared with 
the upcoming Streamstats application for delivering streamflow statistics 
over the web. OSW will provide more information on Streamstats in the near 

NFF, Version 3, requires a computer running Windows 98/NT Version 4.0 or 
newer with service pack 5 or higher. For optimal performance, a processor 
running at 400 megahertz or faster with at least 64 megabytes of memory is 

The software can be downloaded by ftp from 
( After connecting to the server, change directories to 
/var/ftp/pub/OSW/kries, get NFFbeta7.exe and StreamStatsDB.mdb, and copy 
these to the Temp directory or other suitable location on your computer. 
To install the software double-click on NFFbeta7.exe in Windows Explorer, 
choose the directory in which to install the program (default is 
C:\Program Files\NFF) and follow the simple directions. Next, copy 
StreamStatsDB.mdb to the NFF program directory. The installation will put 
an icon on your desktop and an entry in the Programs listing accessed from 
your Start button. Clicking on either of these will start the program. 

After starting NFF, click on the Help pull-down menu at the top left of 
the window, then on Contents. This will cause the Help file to open. At 
present the help file contains the documentation from the previous version 
of NFF and the User's Manual for the new version. The documentation will 
be replaced before Version 3 is released to the public by documentation 
from a new Water Resources Investigations Report that is being prepared. 
The Users' Manual provides complete instructions for use of the new 

We ask you to test each equation that applies to your District by February 
28, 2002. In addition, please assure that the applicable limits shown for 
each basin characteristic in the Edit Scenario window are correct. Please 
inform Kernell Ries (, 703-648-5307) of the results of your 
tests, and provide him with any comments you have about the new software 
or the help file. Kernell is also available to answer any questions you 
may have on operating the program. 

Your assistance will help assure that we provide the best possible product 
to the public, and it is greatly appreciated.