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Floodplain Terminology and Additional Resources
Terms and Definitions Used to Discuss Floodplains:
Base Flood Elevation (BFE)
The elevation of the flood that has a 1 percent chance of occurring in a given year. This is also known as the 1 percent annual chance flood or the 100 year flood.
A FEMA form used to record the elevations of a building. Completing the form requires that a survey be conducted by a registered professional engineer or land surveyor. The elevation certificate is used to determine insurance rates for Post-FIRM structures and can be used to support a Letter of Map Amendment (LOMA) application.
Flood Insurance Rate Map (FIRM)
An official map of the community issued by FEMA in support of the National Flood Insurance Program (NFIP). The map delineates Special Flood Hazard Areas (SFHAs), flood zones, and Base Flood Elevations (BFEs) where applicable.
Flood Insurance Study (FIS)
A report that summarizes the processes used to produce the Flood Insurance Rate Maps (FIRMs) for a community. Technical data, such as flood profiles and floodway data tables, are included in this report.
Flood Risk Zones
Zones delineated on the Flood Insurance Rate Map that impact insurance rates and building code requirements.
Letter of Map Amendment (LOMA)
A LOMA is an official amendment by letter to an effective FIRM map. A LOMA results from the FEMA review of property or structure related data submitted by an owner who believes that the property has incorrectly been included in the SFHA on the FIRM. When issued, a LOMA establishes that a specific property or structure is not located in the SFHA.
Letter of Map Revision (LOMR)
A LOMR is an official revision to the currently effective FIRM or FIS. It is used to change flood zones, floodplain and floodway delineations, flood elevations, incorporate flood control projects, update base mapping, etc. A LOMR is the result of the FEMA review of technical data submitted through the community that updates the data used to create the FIRM. When issued, a LOMR usually results in the reprinting of a portion of the FIRM where revisions have occurred.
The channel of a river or other watercourse and the adjacent land areas that must be reserved in order to discharge the base flood without cumulatively increasing the water surface elevation more than a designated height.
Special Flood Hazard Area (SFHA)
The land in the floodplain within a community subject to a 1 percent or greater chance of flooding in any given year. The SFHA is delineated on the Community's Flood Insurance Rate Map (FIRM).
Any reconstruction, rehabilitation, addition, or other improvement of a structure, the cost of which equals or exceeds 50 percent of the market value of the structure before the start of construction of the improvement. This term does not include 1) Any project for improvement of a structure to correct existing violations of state or local health, sanitary, or safety code specifications which have been identified by the local code enforcement official and which are the minimum necessary to assure safe living conditions 2) Any alteration of a "historic structure", provided that the alteration will not preclude the structures continued designation as a "historic structure".
Damage of any origin sustained by a structure whereby the cost of restoring the structure to its before damage condition would equal or exceed 50 percent of the market value of the structure before the damage occurred. If a structure is substantially damaged, its repair would qualify as a substantial improvement, and the substantial improvement requirements would have to be met as part of the repair.
For more NFIP definitions, see Section 59.1 of the Code of Federal Regulations.
- Floodplain FAQs
- Homeowner's Guide to Retrofitting: Six Ways to Protect Your Home from Flooding (FEMA)
- Protecting Building Utilities from Flood Damage [PDF]
- Myths and Facts about the NFIP [PDF]
- Building Permit Fact Sheet [PDF]
- NFIP Frequently Asked Questions [PDF]
- Floodplain Review Flowchart [PDF]
- Letter to Property Owners [PDF]
- Floodplain Management Program in Washington DC [PDF]