Floodplain Definitions

Request email notification when page changes E-Notify

Return to Floodplain home page
Press 'ctrl F' to search document

Definitions
This list of terms is intended to include those that have specific meaning to the National Flood Insurance Program (NFIP). In a few instances, standard industry terms have been added for additional focus and emphasis..

Anchored - Adequately secured to prevent flotation, collapse or lateral movement.
Base Flood - A flood having a one (1) percent change of being equaled or exceeded in any given year.
Base Flood Elevation (BFE) - The water surface elevation of the one (1) percent annual chance flood.  The height in relation to mean sea level expected to be reached by the waters of the base flood at pertinent points in the floodplains of coastal and riverine areas. The BFE is shown on the Flood Insurance Rate Map (FIRM) for zones AE, AH, A1–A30, AR, AR/A, AR/AE, AR/A1– A30, AR/AH, AR/AO, V1–V30 and VE.
Basement - Any area of the building having its floor subgrade (below ground level) on all sides.
Breakaway Wall - A wall that is not part of the structural support of the building and is intended through its design and construction to collapse under specific lateral loading forces, without causing damage to the elevated portion of the building or supporting foundation system.
B
uilding
-- A structure with 2 or more outside rigid walls and a fully secured roof, that is affixed to a permanent site; or
-- A manufactured home (a "manufactured home," also known as a mobile home, is a structure built on a permanent chassis, transported to its site in 1 or more sections and affixed to a permanent foundation); or
-- A travel trailer without wheels, built on a chassis and affixed to a permanent foundation, that is regulated under the community's floodplain management and building ordinances or laws.
-- "Building" does not mean a gas or liquid storage tank or a recreational vehicle, park trailer or other similar vehicle, except as described above.
Conditional Letter of Map Revision (CLOMR) - FEMA's comment on a proposed project that would, upon construction, affect the hydrologic or hydraulic characteristics of a flooding source and thus result in the modification of the existing regulatory floodway, the effective base flood elevations (BFEs), or the special flood hazard area (SFHA). The letter does not revise an effective NFIP map, it indicates whether the project, if built as proposed, would be recognized by FEMA.  FEMA charges a fee for processing a CLOMR to recover the costs associated with the review. Building permits cannot be issued based on a CLOMR, because a CLOMR does not change the NFIP map.
Development - Any man-made change to improved or unimproved real estate, including, but not limited to buildings or other structures, mining, dredging, filling, grading, paving, excavation or drilling operations or storage of equipment or materials.
Flood or Flooding - A general and temporary condition of partial or complete inundation of normally dry land areas from:
   (1)   The overflow of inland or tidal water.
   (2)   The unusual and rapid accumulation or runoff of surface waters from any source.
Flood Insurance Rate Map (FIRM) - The official map on which FEMA has delineated both the areas of special flood hazards and the risk premium zones applicable to the community.
Flood Insurance Study - The official report provided by FEMA that includes flood profiles, the flood boundary-floodway map, and the water surface elevation of the base flood.
Floodplain or flood-prone area - Any land area susceptible to being inundated by water from any source (see definition of "flooding").
Floodproofing - Any combination of structural and non-structural additions, changes, or adjustments to structures which reduce or eliminate flood damage to real estate or improved real property, water and sanitary facilities, structures and their contents.
Freeboard - A factor of safety usually expressed in feet above a flood level for purposes of floodplain management. "Freeboard" tends to compensate for the many unknown factors that could contribute to flood heights greater than the height calculated for a selected size flood and floodway conditions, such as wave action, bridge openings, and the hydrological effect of urbanization of the watershed.
Highest adjacent grade - The highest natural elevation of the ground surface prior to construction next to the proposed walls of a structure.
Historic structure - Any structure that is:
   (1)   Listed individually in the National Register of Historic Places (a listing maintained by the Department of Interior) or preliminarily determined by the Secretary of the Interior as meeting the requirements for individual listing on the National Register;
   (2)   Certified or preliminarily determined by the Secretary of the Interior as contributing to the historical significance of a registered historic district or a district preliminarily determined by the Secretary to qualify as a registered historic district;
   (3)   Individually listed on a state inventory of historic places in states with historic reservation programs which have been approved by the Secretary of the Interior; or
   (4)   Individually listed on a local inventory of historic places in communities with historic preservation programs that have been certified either:
      (a)   By an approved state program as determined by the Secretary of the Interior; or
      (b)   Directly by the Secretary of the Interior in states without approved programs.
Improvement - Any repair, reconstruction, rehabilitation, addition, or alteration of a structure, the cost of which does not equal or exceed fifty (50) percent of the market value of the structure.
Letter of Determination Review (LODR) - FEMA's ruling on the determination made by a lender or third party that a borrower's building is in a Special Flood Hazard Area(SFHA). A LODR deals only with the location of a building relative to the SFHA boundary shown on the Flood Insurance Rate Map (FIRM).
Letter of Map Amendment (LOMA) - An amendment to the currently effective FEMA map which establishes that a property is not located in a Special Flood Hazard Area (SFHA). A LOMA is issued only by FEMA.
Letter of Map Revision (LOMR) - An official amendment to the currently effective FEMA map. It is issued by FEMA and changes flood zones, delineations and elevations. 
Lowest Adjacent Grade- The lowest point of the ground level immediately next to a building.
Lowest FloorThe lowest floor of the lowest enclosed area (including a basement). An unfinished or flood-resistant enclosure, usable solely for parking of vehicles, building access or storage in an area other than a basement area, is not considered a building's lowest floor provided that such enclosure is not built so as to render the structure in violation of requirements.
Manufactured (Mobile) Home - A structure, transportable in one (1) or more sections, which is built on a permanent chassis and is designed for use with or without a permanent foundation when attached to the required utilities. The term "manufactured home" does not include a "recreational vehicle."
Map - A Flood Insurance Rate Map (FIRM), Flood Boundary and Floodway Map (FBFM), and Flood Hazard Boundary Map (FHBM) are all flood maps that have been produced by FEMA. The FIRM is the most common map and most communities have this type of map. At a minimum, flood maps show flood risk zones and their boundaries, and may also show floodways and Base Flood Elevations (BFEs). The FBFM is a version of a flood map that shows only the floodway and flood boundaries. The FBFM is no longer produced; current FIRMs include all of this information. The FHBM is an older version of a flood map and is based on approximate data.
Map Revision - A change in the Flood Hazard Boundary Map (FHBM) or Flood Insurance Rate Map (FIRM) for a community which reflects revised zone, base flood or other information.
Mean Sea Level - The National Flood Insurance Program, the National American Vertical Datum (NAVD) of 1988 datum, to which base flood elevations shown on a community's Flood Insurance Rate Map are referenced.
New Construction - The purposes of determining insurance rates, structures for which the "start of construction" commenced on or after the effective date of an initial FIRM or after December 31, 1974, whichever is later, and includes any subsequent improvements to such structures. For floodplain management purposes, new construction means structures for which the start of construction commenced on or after the effective date of a floodplain management regulation adopted by a community and includes any subsequent improvements to such structures.
Non-Residential Building (including hotel/motel) - This is a commercial or non-habitational building or a mixed-use building that does not qualify as a residential building. This category includes but is not limited to: small businesses, churches, schools, farm buildings (including grain bins and silos), garages, poolhouses, clubhouses, recreational buildings, mercantile buildings, agricultural and industrial buildings, warehouses, nursing homes, licensed bed and breakfasts and hotels and motels with normal room rentals for less than 6 months.
Post-FIRM BuildingA building for which construction or substantial improvement occurred after December 31, 1974 or on or after the effective date of an initial Flood Insurance Rate Map (FIRM), whichever is later.
Pre-FIRM BuildingA building for which construction or substantial improvement occurred on or before December 31, 1974 or before the effective date of an initial Flood Insurance Rate Map (FIRM).
Proper Openings - Enclosures (Applicable to Zones A, A1-A30, AE, AO, AH, AR and AR Dual) - All enclosures below the lowest elevated floor must be designed to automatically equalize hydrostatic flood forces on exterior walls by allowing for the entry and exit of floodwaters. A minimum of 2 openings, with positioning on at least 2 walls, having a total net area of not less than 1 square inch for every square foot of enclosed area subject to flooding must be provided. The bottom of all openings must be no higher than 1 foot above the higher of the exterior or interior (adjacent) or floor immediately below the openings.
Recreational Vehicle - A vehicle which is:
   (a)   Built on a single chassis;
   (b)   Four hundred (400) square feet or less when measured at the largest horizontal projection;
   (c)   Designed to be self-propelled or permanently towable by a light duty truck; and
   (d)   Designed primarily not for use as a permanent dwelling but as temporary living quarters for recreational, camping, travel, or seasonal use.
Regulatory Floodway - 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. Communities must regulate development in these floodways to ensure that there are no increases in upstream flood elevations. For streams and other watercourses where FEMA has provided Base Flood Elevations (BFEs), but no floodway has been designated, the community must review floodplain development on a case-by-case basis to ensure that increases in water surface elevations do not occur, or identify the need to adopt a floodway if adequate information is available.
Riverine - Relating to, formed by, or resembling a river (including tributaries), streams, brooks, etc.
Special Flood Hazard Area (SFHA) - An area having special flood, mudslide (i.e., mudflow), or flood-related erosion hazards, and shown on an FHBM or FIRM as Zone A, AO, A1-30, AE, AR, AR/A1-30, AR/AE, AR/AO, AR/AH, AR/A, A99, AH, VO, V1-30, VE, V, M, or E.
Start of Construction Includes Substantial Improvement - The date the building permit was issued, provided the actual start of construction, repair, reconstruction, rehabilitation, addition placement, or other improvement was within one hundred eighty (180) days of the permit date. The actual start means either the first placement of permanent construction of a structure on a site, such as the pouring of slab or footings, the installation of piles, the construction of columns, or any work beyond the stage of excavation; or the placement of a manufactured home on a foundation. Permanent construction does not include land preparation, such as clearing, grading or filling; nor does it include the installation of streets and/or walkways; nor does it include excavation for a basement, footings, piers, or foundations, or the erection of temporary forms; nor does it include the installation on the property of accessory buildings, such as garages or sheds not occupied as dwelling units or not part of the main structure.  For a substantial improvement, the actual start of construction means the first alteration of any wall, ceiling, floor, or other structural part of a building, whether or not that alteration affects the external dimensions of the building.
Structure - For floodplain management purposes, a walled and roofed building, including a gas or liquid storage tank, that is principally above ground, as well as a manufactured home.  Anything constructed or placed on the ground or attached to the ground, including, but without limitations, buildings, factories, sheds, walls, fences, culverts, conduits or any other manmade objects.
Substantial damage - Damage of any origin sustained by a structure whereby the cost of restoring the structure to its before damaged condition would equal or exceed fifty (50) percent of the market value of the structure before the damage occurred.
Substantial improvement - Any repair, reconstruction, rehabilitation, addition, or improvement of a structure, the cost of which equals or exceeds fifty (50) percent of the market value of the structure either:
   (1)   Before the improvement or repair is started; or
   (2)   If the structure has been damaged and is being restored, before the damage occurred. For the purpose of this definition, "substantial improvement" is considered to occur when the first alteration of any wall, ceiling, floor, or other structural part of the building commences, whether or not that alteration affects the external dimensions of the structure.
   The term does not however include either:
   (1)   Any project for improvement of a structure to comply with existing state or local health, sanitary, or safety code specifications, which are solely necessary to assure safe living conditions; or
   (2)   Any alteration of a structure listed on the National Register of Historic Places or a state inventory of historic places.
Variance - A grant of relief to a person from the requirements of this chapter when specific enforcement would result in unnecessary hardship. (For full requirements, see Section 60.0 of the National Flood Insurance Program Regulations.)
Violation - The failure of a structure or other development to be fully compliant with the community's floodplain management regulations. A structure or other development without the elevation certificate, other certifications, or other evidence of compliance required in section 60.3(b)(5), (c)(4), (c)(10), (d)(3), (e)(2), (e)(4), or (e)(5) is presumed to be in violation until such time as that documentation is provided.
Water Surface elevation - The height, in relation to the National Geodetic Vertical Datum (NGVD) of 1929, (or other datum, where specified) of floods of various magnitudes and frequencies in the floodplains of coastal or riverine areas.