Accessory Structure

A structure which is on the same parcel of property as the principal structure to be insured and the use of which is incidental to the use of the principal structure.

Area of Shallow Flooding

A designated AO, AH, AR/AO, AR/AH, or VO zone on a community’s Flood Insurance Rate Map (FIRM) with a one (1) percent or greater annual chance of flooding to an average depth of one to three feet where a clearly defined channel does not exist, where the path of flooding is unpredictable, and where velocity flow may be evident. Such flooding is characterized by ponding or sheet flow.

Area of Special Flood Hazard

see definition for “Special Flood Hazard Area”.

Base Flood

The flood having a one (1) percent chance of being equaled or exceeded in any given year.

Base Flood Elevation (BFE)

The elevation of the crest of the base flood or 100-year flood. The height, as established in relation to the North American Vertical Datum (NAVD) of 1988 (or other datum where specified), 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.


Any area of a building having its floor subgrade (below ground level) on all sides.

Coastal A Zone

Area within a special flood hazard area, landward of a V Zone or landward of an open coast without mapped V Zones. The principal source of flooding must be astronomical tides, storm surges, seiches, or tsunamis, not riverine flooding. During the base flood conditions, the potential for breaking wave heights shall be greater than or equal to 1.5 feet.


Any man-made change to improved or unimproved real estate, including but not limited to the construction of buildings or other structures, mining, dredging, filling, grading, paving, excavation or drilling operations or storage of equipment or materials.

Federal Emergency Management Agency (FEMA)

The federal agency that administers the National Flood Insurance Program (NFIP).

Flood or Flooding

A general and temporary condition of partial or complete inundation of normally dry land areas from either the overflow of inland or tidal waters, or the unusual and rapid accumulation or runoff of surface waters from any source.

Flood Insurance Rate Map (FIRM)

The official map of a community on which the Federal Insurance Administrator has delineated both the special hazard areas and the risk premium zones applicable to the community. A FIRM that has been made available digitally is called a Digital Flood Insurance Rate Map (DFIRM).

Flood Insurance Study (FIS)

The official study of a community in which the Federal Emergency Management Agency (FEMA) has conducted a technical engineering evaluation and determination of local flood hazards, flood profiles and water surface elevations. The Flood Insurance Rate Maps (FIRM), which accompany the FIS, provide both flood insurance rate zones and base flood elevations, and may provide the regulatory floodway limits.

Flood Proofing

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.


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. For the purposes of these regulations, the term “Regulatory Floodway” is synonymous in meaning with the term “Floodway”.


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.

Functionally Dependent Use of Facility

A use that cannot perform its intended purpose unless it is located or carried out in close proximity to water. The term includes only docking facilities, port facilities that are necessary for the loading and unloading of cargo or passengers, and ship building and ship repair facilities.

Highest Adjacent Grade (HAG)

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:  (a) Listed individually in the National Register of Historic Places (a listing maintained by the Department of the Interior) or preliminarily determined by the Secretary of the Interior as meeting the requirements for individual listing on the National Register; (b) Certified or preliminarily determined by the Secretary of the Interior as contributing to the historic significance of a registered historic district or a district preliminarily determined by the Secretary to qualify as a registered historic district; (c) Individually listed on a state inventory of historic places in states with historic preservation programs which have been approved by the Secretary of the Interior; or (d) Individually listed on a local inventory of historic places in communities with historic preservation programs that have been certified either:  (1) By an approved state program as determined by the Secretary of the Interior or (2) Directly by the Secretary of the Interior in states without approved programs.

Limit of Moderate Wave Action (LiMWA)

An advisory line indicating the limit of the 1.5 foot wave height during the base flood.

Lowest Floor

The lowest floor of the lowest enclosed area (including 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 the applicable non-elevation design requirements of § 60.3.

Manufactured 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”.

Manufactured Home Park or Manufactured Home Subdivision

A parcel or contiguous parcels of land divided into two (2) or more manufactured home lots for rent or sale.

Market Value

Market value is the price of a structure that a willing buyer and seller agree upon. This can be determined by an independent appraisal by a professional appraiser; the property’s tax assessment, minus land value; the replacement cost minus depreciation of the structure; the structure’s Actual Cash Value. 

New Construction

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.

New Manufactured Home Park or Manufactured Home Subdivision

A manufactured home park or manufactured home subdivision for which the construction of facilities for servicing the lots on which the manufactured homes are to be affixed (including at a minimum, the installation of utilities, the construction of streets, and either final site grading or the pouring of concrete pads) is completed on or after the effective date of floodplain regulations adopted by the community.

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 a temporary living quarters for recreational, camping, travel, or seasonal use.

Sheet Flow Area

see definition for “Area of Shallow Flooding”.

Special Flood Hazard Area (SFHA)

The land in the floodplain within a community subject to a one (1) percent or greater chance of flooding in any given year. After detailed ratemaking has been completed in preparation for publication of the flood insurance rate map, Zone A usually is refined into Zones A, AO, AH, A1-30, AE, A99, AR, AR/A1-30 ,AR/AE, AR/AO, AR/AH, AR/A, VO, or V1-30, VE or V. For purposes of these regulations, the term “special flood hazard area” is synonymous in meaning with the phrase “area of special flood hazard”.


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. For insurance purposes, means:

  1. A building with two or more outside rigid walls and a fully secured roof, that is affixed to a permanent site;
  2. A manufactured home (“a manufactured home,” also know as a mobile home, is a structure; built on permanent chassis, transported to its site in one or more sections, and affixed to a permanent foundation); or
  3. 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.

For the latter purpose, “structure” does not mean recreational vehicle or a park trailer or other similar vehicle, except as described in paragraph (3) of this definition, or a gas or liquid storage tank.

Substantial Damage

Damage of any origin sustained by a structure, whereby the cost of restoring the structure to before damaged condition would equal or exceed fifty (50) percent of the market value of the structure before the damage occurred.

Substantial Improvement

Any reconstruction, rehabilitation, addition or other improvements to a structure, the cost of which equals or exceeds fifty (50) percent of the market value of the structure before the “start of construction” of the improvement. This term includes structures which have incurred “substantial damage”, regardless of the actual repair work performed. The term does not, however, include:

  1. Any project 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; or
  2. Any alteration of the “historic structure”, provided that the alteration will not preclude the structure’s continued designation as a “historic structure”.


A grant of relief by a community from the terms of the floodplain management ordinance that allows construction in a manner otherwise prohibited and where specific enforcement would result in unnecessary hardship.


Failure of a structure or other development to be fully compliant with the community’s floodplain management ordinance. Construction or other development without required permits, lowest floor elevation documentation, flood-proofing certificates or required floodway encroachment calculations is presumed to be in violation until such time as that documentation is provided.