Explanation of Terms

Accretion - May be either natural or artificial. Natural accretion is the buildup of land, solely by the action of the forces of nature, on a beach by deposition of water or airborne material. Artificial accretion is a similar buildup of land by human accretions, such as accretion formed by a groin, breakwater, or beach fill deposited by mechanical means.

A-zone - Area subject to inundation by 100-year flooding where wave action does not occur or where waves are less than 3 feet high; designated Zone A, AE, A1-A30, A0, AH, or AR on a Flood Insurance Rate Map.

Armor - To protect slopes form erosion and scour by flood waters. Techniques of armoring include the use of riprap, gabions, or concrete.

Base flood - Flood that has a 1-percent probability of being equal or exceeded in any given year. Also known as the 100-year flood.

Base Flood Elevation (BFE) - Elevation of the base flood in relation to a specified datum, such as the National Geodetic Vertical Datum. The Base Flood Elevation is the basis of the insurance and floodplain management requirements of the National Flood Insurance Program.

Basic Report - A flood hazard determination which is provided without Life of Loan monitoring. Commonly ordered for short-term loans.

Beach nourishment - Replacement of beach sand removed by ocean waters. It may be brought about naturally by alongshore transport or artificially by deposition of dredged materials.

Breakaway walls - Under the National Flood Insurance Program, walls that are not part of the structural support of the building and are designed and constructed to break away or collapse under specified lateral loads imposed by flood waters before transmitting damaging forces to the building and its supporting foundation system. Breakaway walls are required by the National Flood Insurance Program regulations for the portions of buildings below the Base Flood Elevation in a Coastal High Hazard Area, also referred to as V-zones, and are recommended in areas where flood waters could flow at significant velocities (usually greater than 4 feet per second) or could contain ice or other debris. 

Breakwater - A structure protecting a shore area, harbor, anchorage, or basin from waves.

Building code - Regulations adopted by local governments that establish standards for construction, modification, and repair of buildings and other structures.

Bulkhead - Wall or other structure, often of wood, steel, or concrete, designed to retain or prevent sliding or erosion of the land. Occasionally, bulkheads are used to protect against wave action.

Coastal barrier - Depositional geologic feature such as a bay barrier, tombolo, barrier spit, or barrier island that consists of unconsolidated sedimentary materials; is subject to wave, tidal, and wind energies; and protects landward aquatic habitats from direct wave attack.

Coastal Barrier Resource Act of 1982 (CBRA) - Act (Pub. L. 97-348) that established the Coastal Barrier Resources System. The act prohibits the provision of new flood insurance coverage on or after October 1, 1983, for any new construction or substantial improvements of structures located on any designated undeveloped coastal barrier within the Coastal Barrier Resources System.

Coastal flood hazard area - Area, usually along an open coast, bay, or inlet, that is subject to inundation by storm surge and, in some instances, wave action caused by storms or seismic forces.

Coastal High Hazard Area - Area of special flood hazard, designated Zone V, VE, or V1-V30 on a Flood Insurance Rate Map that extends from offshore to the inland limit of a primary frontal dune along an open coast and any other area subject to high-velocity breaking waves of 3 feet or more in height caused by storms or seismic forces.

Coastline - (1) Technically, the line that forms the boundary between the coast and the shore. (2) Commonly, the line that forms the boundary between the land and the water.

Development- Under the National Flood Insurance Program, 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.

Downdrift - The direction of predominant movement of littoral materials.

E-zone - An area along the coast where waves and other forces are anticipated to cause significant erosion within the next 60 years and may result in the damage or loss of buildings and infrastructure.

Elevation Certificate - An elevation certificate is a document provided by a certified Surveyor showing actual elevation measurements taken on-site. This document is a requirement when applying for a LOMA or LOMR.

Episodic erosion - Erosion induced by a single storm event. Episodic erosion considers the vertical component of two factors: general beach profile lowering and localized conical scour around foundation supports. Episodic erosion is relevant to foundation embedment depth and potential undermining.

Erosion - Wearing away of the land surface by detachment and movement of soil and rock fragments, during a flood or storm or over a period of years, through the action of wind, water, or other geologic processes.

Erosion Hazard Area (EHA) – Area anticipated to be lost to shoreline retreat over a given period of time. The projected inland extent of the area is measured in years times the average annual long-term recession rate.

Federal Emergency Management Agency (FEMA) - Independent agency created in 1978 to provide a single point of accountability for all Federal activities related to disaster mitigation and emergency preparedness, response and recovery. FEMA administers the National Flood Insurance Program.

FEMA Standard Form - FEMA has mandated that all FZD reports be provided on the standardized form since January of 1996.

Federal Insurance Administration (FIA) - The component of the Federal Emergency Management Agency directly responsible for administering the flood insurance aspects of the National Flood Insurance Program.

Flood - Under the National Flood Insurance Program, a general and temporary condition or partial or complete inundation of normally dry land areas from (1) the overflow of inland or tidal waters, (2) the unusual and rapid accumulation or runoff of surface waters from any source, or (3) mudflows or the sudden collapse of shoreline land.

Flood depth - Height of the flood water surface above the ground surface.

Flood elevation - Height of the water surface above an established elevation datum, e.g., National Geodetic Vertical Datum, North American Vertical Datum, Mean Sea Level.

Flood hazard area - The greater of the following: (1) the Special Flood Hazard Area or (2) the area designated as a flood hazard area on a community's legal flood hazard map, or otherwise legally designated. 

Flood Insurance - Insurance coverage provided under the National Flood Insurance Program.

Flood Insurance Rate Map (FIRM) - Map of a community, prepared by the Federal Emergency Management Agency, that shows both the special hazard areas and the risk premium zones applicable to the community. The latest FIRM issued for a community is referred to as the "effective" FIRM.

Flood Insurance Study (FIS) - Examination, evaluation, and determination of flood hazards and, if appropriate, corresponding water surface elevations in a community or communities, or examination, evaluation, and determination of mudslide (i.e., mudflow) and/or flood-related erosion hazards in a community or communities.

Flood-related erosion area or flood-related erosion prone area - Land area adjoining the shore of a lake or other body of water which, because of the composition of the shoreline or bank and high water levels or wind-driven currents, is likely to suffer damage from erosion caused by flood forces.

Floodplain - Any land area, including watercourse, susceptible to partial or complete inundation by water from any source.

Floodplain management - Operation of an overall program of corrective and preventive measures for reducing flood damage, including but not limited to emergency preparedness plans, flood control works, and floodplain management regulations.

Frontal dune - Ridge or mound of unconsolidated sandy soil, extending continuously alongshore landward of the sand beach and defined by relatively steep slopes abutting markedly flatter and lower regions on each side.

Groin - A shore protection structure built (usually perpendicular to the shoreline) to trap littoral drift or retard erosion of the shore.

Hand Mapping - A process used by SRG whereby a research staff member physically references the appropriate FEMA flood map panel and tax assessment plat map before making his/her determination for SRG’s client.

High-velocity wave action - Condition in which wave heights are greater than or equal to 3.0 feet or wave run up elevations reach 3.0 or more feet above grade.

Hurricane - Tropical cyclone, formed in the atmosphere over warm ocean areas, in which wind speeds reach 74 miles per hour or more and blow in a large spiral around a relatively calm center or "eye." Hurricane circulation is counter-clockwise in the Northern Hemisphere and clockwise in the Southern Hemisphere. 

Jetty - A structure extending into a body of water, designed to prevent shoaling of a channel by littoral materials and to direct and confine the stream or tidal flow. Jetties are built at the mouths of rivers or tidal inlets to help deepen and stabilize a channel.

Littoral - Of or pertaining to the shore, especially of the sea.

Littoral Drift - Movement of sand by littoral (longshore) currents in a direction parallel to the beach along the shore.

Littoral Transport - The movement of littoral drift in the littoral zone by waves and currents. Includes movement parallel and perpendicular to the shore.

Lowest floor - The lowest floor of the lowest enclosed area (including basement) of a structure. An unfinished or flood-resistant enclosure, usable solely for parking of vehicles, building access, or storage in an area  other than a basement, is not considered a building's lowest floor.

Mean High Water - The average height of the high waters over a 19-year period.

Mean Sea Level (MSL) - Average height of the sea for all stages of the tide, usually determined from hourly height observations over a 19-year period on an open coast or in adjacent waters having free access to the sea. See National Geodetic Vertical Datum.

National Flood Insurance Program (NFIP) - Federal program created by Congress in 1968 that makes flood insurance available in communities that enact satisfactory floodplain management regulations.

National Geodetic Vertical Datum (NGVD) - Datum established in 1929 and used as a basis for measuring flood, ground, and structural elevations, previously referred to as Sea Level Datum or Mean Sea Level. The Base Flood Elevations shown on most of the Flood Insurance Rate Maps issued by the Federal

Emergency Management Agency are referenced to NGVD.

100-year flood - See Base Flood.

Partial Determination - A determination which can not be accurately completed until a Survey or Site plan is forwarded.

Post-FIRM - For insurance purposes, post-FIRM construction in a given community is construction or substantial improvement of a structure that began after December 31, 1974, or on or after the effective date of the first Flood Insurance Rate Map for the community, whichever is later. For floodplain management purposes, post-FIRM construction in a given community means structures for which the start of new or substantial improvement construction began before the effective date of the floodplain management regulation adopted by the community.

Primary frontal dune - Continuous or nearly continuous mound or ridge of sand with relatively steep seaward and landward slopes immediately landward and adjacent to the beach and subject to erosion and overtopping from high tides and waves during major coastal storms. The inland limit of the primary frontal dune occurs at the point where there is a distinct change from a relatively steep slope to a relatively mild slope.

Retrofit - In flood proofing, any change made to a structure designed to reduce or eliminate damage to that structure from flooding erosion.

Revetment – A facing of stone, cement, sandbags, or other materials built to protect a scarp, embankment, or short structure against erosion or scour caused by flood waters or wave action.

Sand dunes - Natural or artificial ridges or mounds of sand landward of the beach.

Sand wave - A large wavelike sediment feature composed of sand in very shallow water. Wavelength may reach 100 meters; amplitude is about 0.5 meter.

Scarp - An almost vertical slope along the beach caused by erosion by wave action. It may vary in height from a few centimeters to a meter or so, depending on wave action and the nature and composition of the beach.

Scour – Removal of soil or fill material by the flow of flood waters. The term is frequently used to describe storm-induced, localized conical erosion around pilings and other foundation supports where the obstruction of flow increases turbulence. See erosion.

Seawall - A structure separating land and water areas, primarily designed to prevent erosion and other damage from wave actions.

Shear wall - Load-bearing or non-load-bearing wall that transfers in-plane lateral forces from lateral loads acting on a structure to its foundation.

Shore - The narrow strip of land in immediate contact with the sea, including the zone between high and low water lines. A shore of unconsolidated material usually is called a beach. 

Shoreline - The intersection of a specified plane of water with the shore or beach. The line delineating the shoreline on natural ocean service nautical charts and survey approximates the mean high water line.

Shoreline retreat - Progressive movement of the shoreline in a landward direction caused by the composite effect of all storms considered over decades and centuries (expressed as an annual average erosion rate). Shoreline retreat considers the horizontal component of erosion and is relevant to long-term land use decisions and the siting of buildings.

Special Flood Hazard Area (SFHA) – An area within a floodplain having a 1 percent or greater chance of flood occurrence in any given year (100-year floodplain); represented on Flood Insurance Rate Maps by darkly shaded areas with zone designations that include the letter A or V.

Storm surge - Rise in the water surface above normal water level on the open coast due to the action of wind stress and atmospheric pressure on the water surface.

Structure - Under the National Flood Insurance Program, 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 coverage purposes.

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 50 percent of the market value of the structure before the damage.

Substantial improvement - 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 includes structures, which have incurred substantial damage, regardless of the actual repair work performed.

Surge - See Storm surge.

Tsunami - Great sea wave produced by submarine earth movement or volcanic eruption.

Undermining - Process whereby the vertical component or erosion or scour exceeds the depth of the base of a building foundation or the level below which the bearing strength of at the foundation is compromised.

Updrift - The direction opposite that of the predominant movement of littoral materials. 

V-zone - also known as Coastal High Hazard Area. Flood hazard zone that corresponds to the 100-year floodplain that is subject to high velocity wave action from coastal storms or seismic sources; designated Zone VO, V1-30, VE, or V on a Flood Insurance Rate Map.

Water surface elevation - Height of the water surface above an established elevation datum, e.g., National Geodetic Vertical Datum, North American Vertical Datum, Mean Sea Level, reached by floods of various magnitudes and frequencies in the floodplains of coastal, lacustrine, and riverine areas.

Wave height - Vertical distance between a wave crest and the preceding trough.

Wind tide – The vertical rise in the stillwater level on the leeward side of a body of water caused by wind stresses on the surface of the water.

X-zone – A flood hazard zone outside the 100-year floodplain, which have moderate to minimal risk. Older maps differentiate the X zone into Zones B and C, which represent moderate and minimal flood risks, respectively.

Zone – A geographical area shown on a Flood Insurance Rate Map (FIRM) that reflects the severity or type of flooding in the area.