The purpose of the NFF mailing list is to provide information on the U.S. Geological Survey (USGS) National Flood Frequency (NFF) program. NFF is a computer application that is used to estimate peak discharges for unregulated streams. Values (discharges) derived by the program often serve as input for other applications (such as hydraulic computer models) that are used to technically support end-products (map revisions) of the National Flood Insurance Program (NFIP).

Discussion on USGS Regression Equations and the NFF Program

The USGS developed a computer program titled "National Flood Frequency" or "NFF" that estimates the flood frequency and magnitude for ungaged sites through the application of the appropriate regional regression equations. NFF was released in 1993 and does not incorporate any revisions to regional regression equations that occurred after September 30, 1993. Since 1993 a significant number of the regression equations have been revised. The USGS is in the process of revising the NFF computer program to incorporate the updated regression equations. The revised version of NFF will be released soon.

The regional regression equations are currently being used for National Flood Insurance Program (NFIP) purposes. Therefore, FEMA would like to continue with this listserv and discuss issues of interest in the application of the regional regression equations for NFIP purposes. Upon the release of the revised NFF program, the focus of this listserv will shift to assist users in becoming familiar with the revised NFF program and its application for NFIP purposes.

Revisions to the USGS Regression Equations Since the NFF Software was Released

States for which USGS Regression Equations have been revised are listed in the table below.

State Report
Alabama WRIR 95-4199
Alaska WRIR 93-4179
American Samoa WRIR 95-4185
Arizona WSP 2433
Arkansas WRIR 95-4224
Colorado WRIR 99-4190
Connecticut CWRB no. 36
Delaware WRIR 95-4153
Florida-Suwannee WRIR 96-4176
Georgia Rural/Urban WRIR 93-4016/WRIR 95-4017
Hawaii WRIR 94-4052
Idaho WRIR 94-4120
Illinois WRIR 87-4207
Iowa WRIR 00-4233
Kansas WRIR 00-4079
Kentucky-Jefferson Co. Urban WRIR 97-4219
Louisiana LDTD, WRTR no. 60
Maine WRIR 99-4008
Maryland WRIR 95-4154
Massachusetts ASCE journal articles
Minnesota WRIR 97-4249
Missiouri WRIR 95-4231/86-4322
Nebraska WRIR 99-4032
Nevada WSP 2433
New Mexico WRIR 96-4112
North Carolina Rural/Urban WRIR 99-4114 / 96-4084
Oklahoma WRIR 97-4202
Pennsylvania WRIR 00-4189
Puerto Rico WRIR 99-4142
South Carolina WRIR 91-4157 / dWRIR 92-4040
South Dakota WRIR 98-4055
Texas Rural and Urban WRIR 99-4172/98-4015/96-4307/98-4072/98-4178
Utah WSP 2433
Virginia WRIR 94-4148
Washington WRIR 97-4277
West Virginia WRIR 00-4080

States for which Revised USGS Regression Equations are being prepared are listed below.

  • Connecticut
  • Florida - W. Central
  • Idaho
  • Kentucky - rural
  • South Carolina
  • Vermont
  • Wyoming

Locations From Which to Obtain the NFF Program and USGS Regression Equation Documentation

The USGS has established a NFF Web page at: that describes the program, provides a list of States with revised equations, and contains links to Web-based versions of some of the reports that contain the revised equations. This web site will be updated with new information as it becomes available. The new version of the NFF software will also be available at this site when it becomes available. Please contact the respective USGS district offices/libraries regarding obtaining reports that are not available on the Web.

Previous Bulletin Topics

  • Introduction to the NFF Program and USGS regression equations, the applicability of the regression equations, and the advantages and limitations of the regression equations
  • Use of USGS regression equations in the NFIP and Criteria for using USGS regression equations in the NFIP

Upcoming Bulletin Topics

  • Unusual parameters of USGS regression equations and how to obtain them - Part 1
  • Unusual parameters of USGS regression equations and how to obtain them - Part 2
  • Examples in which USGS regression equations are used for NFIP purposes

View the archive page for all Flood Hazard Mapping listservs.

Last Modified: Friday, 22-Jun-2007 11:57:20 EDT