GLOSSARY OF TERMS
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The terms listed below are used throughout this document and in other
FEMA Flood Hazard Mapping Program documents.
0.2-Percent-Annual-Chance Flood—The
flood that has a 0.2-percent chance of being equaled or exceeded in any
given year.
1-Percent-Annual-Chance Flood— The flood that has
a 1-percent chance of being equaled or exceeded in any given year.
2-Percent-Annual-Chance Flood—The flood that has
a 2-percent chance of being equaled or exceeded in any given year.
10-Percent-Annual-Chance Flood—The flood that has
a 10-percent chance of being equaled or exceeded in any given year.
10-Year Flood—See 10-Percent-Annual-Chance Flood.
50-Year Flood—See 2-Percent-Annual-Chance Flood.
100-Year Flood—See 1-Percent-Annual-Chance Flood.
500-Year Flood—See 0.2-Percent-Annual-Chance Flood
A
Accuracy—The degree of correctness attained in
a measurement.
Alluvial Fan—The sedimentary deposit located at
a topographic break, such as the base of a mountain front, escarpment,
or valley side, that is composed of streamflow and/or debris flow sediments
and has the shape of a fan, either fully or partially extended. These
characteristics can be categorized by composition, morphology, and location.
Alluvial Fan Flooding—The flooding that occurs
on an alluvial fan as defined above. The term alluvial fan flooding encompasses
both active alluvial fan flooding and inactive alluvial fan flooding.
Alluvial Fan Flooding (Active)—Flooding that occurs
only on alluvial fans and is characterized by flow path uncertainty so
great that this uncertainty cannot be set aside in realistic assessments
of flood risk or in the reliable mitigation of the hazard. An active alluvial
fan flooding hazard is indicated by three related criteria: (1) flow path
uncertainty below the hydrographic apex; (2) abrupt deposition and ensuing
erosion of sediment as a stream or debris flow loses its ability to carry
material eroded from a steeper, upstream source area; and (3) an environment
where the combination of sediment availability, slope, and topography
creates an ultrahazardous condition for which elevation on fill will not
reliably mitigate the risk.
Alluvial Fan Flooding (Inactive)—Flooding that
is similar to traditional riverine flood hazards, but occurs only on alluvial
fans. Inactive alluvial fan flooding is characterized by flow paths with
a higher degree of certainty in realistic assessments of flood risk or
in the reliable mitigation of the hazard. Unlike active alluvial fan flooding
hazards, an inactive alluvial fan flooding hazard is characterized by
relatively stable flow paths. However, like areas of active alluvial fan
flooding, inactive alluvial fan flooding, may be subject to sediment deposition
and erosion, but to a degree that does not cause flow path instability
and uncertainty.
Alphanumeric Data—Data consisting of both letters
and numbers, and possibly symbols such as punctuation marks.
American Standard Code for Information Interchange (ASCII)—A
popular standard for the exchange of alphanumeric data.
Appeal—The formal objection to proposed or proposed
modified Base Flood Elevations (BFEs), submitted by a community official
or an owner or lessee of real property within the community during the
statutory 90-day appeal period. An appeal must be based on data that show
the proposed or proposed modified BFEs are scientifically or technically
incorrect.
Appeal Period—The statutory period, beginning on
the date of second publication of proposed BFEs and/or proposed modified
BFEs in the local newspaper, during which community officials or owners
or lessees of real property within the community may appeal proposed or
proposed modified BFEs by submitting data to show those BFEs are scientifically
or technically incorrect.
Application/Certification Forms—The comprehensive,
easy-to-use forms that were implemented by FEMA in October 1992 to facilitate
the processing of requests for revisions or amendments to National Flood
Insurance Program maps.
Approved Model—A numerical computer model that
has been accepted by FEMA for use in performing new or revised hydrologic
or hydraulic analyses for National Flood Insurance Program purposes. All
accepted models must meet the requirements set forth in Subparagraph 65.6(a)(6)
of the National Flood Insurance Program regulations.
Approximate Study—A flood hazard study that results
in the delineation of floodplain boundaries for the 1-percent-annual-chance
(100-year) flood, but does not include the determination of BFEs or flood
depths.
Area—The level of spatial measurement referring
to a two-dimensional defined space
Area Not Included (ANI)—An area that is excluded
from the mapping for a subject community because (1) the area is under
the jurisdiction of another community and is shown on the mapping for
that community, or (2) access to the area is limited for security reasons
(e.g., military installations).
Artwork—The various layers prepared by the cartographic
staff that are components of the manually produced Flood Insurance Rate
Map and/or Flood Boundary and Floodway Map.
As-Built—A term used to describe mapping and mapping-related
data that reflect conditions within a floodplain based on flood-control
and other structures being completed.
Assistance Officer (AO) —The FEMA Regional Office
staff person that is responsible for the administration of funding and
funding-related activities for a specific contract or agreement.
Area of Special Consideration (ASC) —The name given
to a special floodprone area around closed-basin lakes. The ASC is an
area that is know to be subject to flooding, but the percent chance of
the area being flooded in any given year is not defined.
Attribute—The descriptive characteristic or quality
of a feature. An attribute value is a measurement assigned to an attribute
for a feature instance.
B
Backwater—Water backed up or retarded in its course
as compared with its normal or natural condition of flow.
Base Flood—The flood that has a 1-percent chance
of being equaled or exceeded in any given year.
Base Flood Elevation (BFE) —The elevation of a
flood having a 1-percent chance of being equaled or exceeded in any given
year.
Base Map—The map of the community that depicts
cultural features (e.g., roads, railroad, bridges, dams, culverts), drainage
features, and corporate limits.
Batch Processing—The system by which computers
process, without operator intervention, all input for an application at
one time to produce the desired input, even though input data might have
been collected periodically.
Bench Mark (BM)—A permanent monument established
by any Federal, State, or local agency, whose elevation and description
are well documented and referenced to the National Geodetic Vertical Datum
of 1929 or the North American Vertical Datum of 1988.
Bit—An abbreviation for binary digit, a number
that can have only a value of 0 or 1.
Block—A group of bytes treated as one unit of information,
sometimes called a physical record.
Buffer Zone—An area of specified distance (radius)
around a map item or items.
Building—See Structure.
Byte—A group of bits that can be stored and retrieved
as a unit.
C
Cell—The defined geometric shape that stores data
or defines an area that is labeled. The most common mapping cell is a
square. Also the basic element of spatial information in raster data structures.
Centroid—The point interior to a polygon whose
coordinates are the averages of the corresponding coordinates for all
points included in the polygon.
Channel—A naturally or artificially created open
conduit that periodically or continuously contains moving water or which
forms a connecting link between two bodies of water.
Chief Executive Officer (CEO)—The official of a
community who has the authority to implement and administer laws, ordinances,
and regulations for that community.
Choropleth Map—A map with shaded or hatched areas.
(Choro = place and pleth = value.)
Coastal Barrier Resources System (CBRS)—A system
of protected coastal areas (including the Great Lakes. The areas within
the CBRS are defined as depositional geologic features consisting of unconsolidated
sedimentary materials; subject to wave, tidal, and wind energies; and
protecting landward aquatic habitats from direct wave attack.
Coastal Flooding—Flooding that occurs along the
Great Lakes, the Atlantic and Pacific Oceans, and the Gulf of Mexico.
Coastal High Hazard Area—An area of special flood
hazard extending from offshore to the inland limit of a primary frontal
dune along an open coast and any other area subject to high-velocity wave
actions from storms or seismic sources.
Code of Federal Regulations (CFR)—The codification
of the general and permanent rules published in the Federal Register by
the Executive Departments and agencies of the Federal Government. National
Flood Insurance Program regulations are printed in Parts 59 through 77
of Title 44 of the CFR.
Community—Any State or area or political subdivision thereof, or
any Indian tribe or authorized tribal organization, or Alaska Native village
or authorized native organization, which has the authority to adopt and
enforce floodplain management regulations for the areas within its jurisdiction.
Community Assistance Call (CAC)—A telephone call
made by FEMA Regional Office staff or the State National Flood Insurance
Program Coordinator to a community to supplement or replace a Community
Assistance Visit.
Community Assistance Program (CAP)—A FEMA program,
funded by the National Flood Insurance Program (NFIP), under which cost-shared
funds are provided to States to provide technical assistance support to
communities participating in the NFIP. The purpose of the CAP is to identify,
prevent, and resolve floodplain management issues in NFIP participating
communities before a flood occurs, or before poor performance or noncompliance
warrant enforcement and intervention by FEMA.
Community Assistance Visit (CAV)—A visit by FEMA
Regional Office staff or the State National Flood Insurance Program Coordinator
to a community to assess whether the community’s floodplain management
program meets National Flood Insurance Program participation requirements.
Community Coordination Meeting—A meeting during
which Flood Hazard Mapping Partners discuss plans for a Flood Map Project,
interim results of a Flood Map Project, and final results of a Flood Map
Project for a particular community or group of communities.
Community Identification Number (CID)—A six-digit
code used by FEMA to identify each community that is potentially subject
to flood hazards.
Community Information System (CIS)—An Oracle database
system used by FEMA to track and report on all communities identified
by FEMA as potentially floodprone, especially with regard to mapping actions,
including Letters of Map Change, taken by FEMA to identify flood hazards
in each community.
Community Rating System (CRS)—A FEMA initiative,
established under the National Flood Insurance Program, to recognize and
reward communities that have implemented floodplain management measures
beyond the minimum required by National Flood Insurance Program regulations.
Under the CRS, those communities that choose to participate voluntarily
may reduce the flood insurance premium rates for property owners in the
community by taking these additional actions.
Compliance Period—The period that begins with the
issuance of a Letter of Final Determination and ends when a new or revised
Flood Insurance Rate Map becomes effective. During the compliance period,
a community must enact and adopt new or revised floodplain management
ordinances required for participation in the National Flood Insurance
Program.
Computer-Assisted Drafting and Design (CADD)—Software
with the capability of assisting the operator with the performance of
standard engineering and architecture design functions.
Conditional Letter of Map Amendment (CLOMA)—The
FEMA response to a requester who believes his or her proposed structure,
when constructed on natural ground at or above the BFE, will be outside
the 1-percent-annual-chance floodplain. CLOMAs may not be issued for unimproved
or undeveloped property.
Conditional Letter of Map Revision (CLOMR)—The
FEMA response to a community request for FEMA’s comment on proposed
alterations to the floodplain conditions within that community. The CLOMR
describes the effect of the proposed project, if constructed as proposed,
on the effective FIRM, FBFM, and/or FIS report. A CLOMR often contains
detailed information on conditions that must be met by a requester before
FEMA will issue a final determination regarding revising the FIRM, FBFM,
and/or FIS report.
Conditional Letter of Map Revision Based on Fill (CLOMR-F)—The
FEMA response to a community request for FEMA’s comment on the effect(s)
that a proposed project involving the placement of earthen fill within
the SFHA will have on the Special Flood Hazard Area designation for one
or more legally defined parcels of land or one or more proposed structures.
Consultation Coordination Officer (CCO)—The individual
on the FEMA Regional Office staff who is responsible for coordinating
with a community on activities related to National Flood Insurance Program.
Contracting Officer (CO)—The FEMA Headquarters
staff person that is responsible for the administration of funding and
funding-related activities for a specific contract or agreement.
Control Point—Any station in a horizontal or vertical
control network that is identified in a dataset of photograph and used
for correlating the data shown in the data set or photograph.
Cooperating Technical Partners (CTP) Initiative—An
innovative FEMA program to create partnerships between FEMA and participating
National Flood Insurance Program communities, regional agencies, and State
agencies that have the interest and capability to become more active participants
in the FEMA Flood Hazard Mapping Program.
Coordinate Geometry (COGO)—The use of bearings
and distances, azimuths, and coordinate locations to enter and describe
graphic data. COGO is usually used for civil engineering and survey applications.
Coordinate Pair—A set of cartesian coordinates
describing the location of a point, line or area (polygon) feature in
relation to the common coordinate system of the data base.
Coordinate System—A particular kind of reference
frame or system, such as plane rectangular coordinates or spherical coordinates,
which use linear or angular quantities to designate the position of points
within that particular reference frame or system (e.g., State Plane).
Countywide Format—A format used by FEMA to show
flooding information for the entire geographic area of a county, including
the incorporated communities in the county, on one map and in one report.
Cultural Features—Railroads, airfields, streets,
roads, highways, levees, dikes, seawalls, dams and other flood-control
structures, and other prominent manmade features and landmarks shown on
a National Flood Insurance Program map.
D
Database—A collection of information related by
a common fact or purpose.
Database Management System (DBMS) —A systematic
approach to maintaining, accessing, and manipulating data base files.
A DBMS may consist of a single program or a collection of task-specific
programs.
Data Capture—The series of operations required
to encode data in a computer-readable form (digitizing).
Data Layer—Refers to data having similar characteristics
being contained in the same plane or overlay (e.g., roads, rivers) of
a Geographic Information System. Usually information contained in a data
layer is thematically related and is designed to be used with other layers.
Dataset or Datafile—A named collection of logically
related data records arranged in a prescribed manner. The physical set
of data of one data type being referred to or being used in the context
of a data processing operation.
Detailed Study—A flood hazard study that, at a
minimum, results in the delineation of floodplain boundaries for the 1-percent-annual-chance
(100-year) flood and the determination of BFEs or flood depths.
Differential Global Positioning System (DGPS)—Global
Positioning System (GPS) positioning techniques that use two or more GPS
receivers, with a base station on a position of known location, and one
or more roving receivers taking GPS measurements at unknown locations.
Digital Data—Data displayed, recorded, or stored
in binary notation.
Digital Elevation Model (DEM)—A file with terrain
elevations recorded for the intersection of a fine-grained grid and organized
by quadrangle as the digital equivalent of the elevation data on a topographic
base map.
Digital Flood Insurance Rate Map (DFIRM)—A Flood
Insurance Rate Map that has been prepared as a digital product, which
may involve converting an existing manually produced FIRM to digital format,
or creating a product from new digital data sources using a Geographic
Information System environment. The DFIRM product allows for the creation
of interactive, multi-hazard digital maps. Linkages are built into an
associated database to allow users options to access the engineering backup
material used to develop the DFIRM, such as hydrologic and hydraulic models,
Flood Profiles, data tables, Digital Elevation Models, and structure-specific
data, such as digital elevation certificates and digital photographs of
bridges and culverts.
Digital Flood Insurance Rate Map–Digital Line Graph (DFIRM-DLG)—The
product created by extracting the flood risk thematic data from the DFIRM.
The format of this product is the U.S. Geological Survey Digital Line
Graph Level 3 optional format. The DFIRM-DLG does not include base map
information, or graphic data required to create a FIRM in hardcopy format.
The DFIRM-DLG is intended to be the primary means of transferring flood
risk data depicted by FIRMs to Geographic Information Systems through
a public domain data exchange format. The DFIRM-DLGs are tiled the to
U.S. Geological Survey 1:24,000 scale topographic map series.
Digital Flood Insurance Rate Map (DFIRM) Spatial Database—A
database designed to facilitate collecting, storing, processing, and accessing
data developed by FEMA, enabling Mapping Partners to share the data necessary
for the DFIRM production and conversion process. Where possible, all mapping
and engineering data elements are linked to physical geographic features
and georeferenced. The use of a Geographic Information System as a component
of the DFIRM spatial database provides the ability to georeference and
overlay the mapping and engineering data, allowing the database to support
a wide variety of existing and forthcoming FEMA engineering and mapping
products.
Digital Line Graph (DLG)—A computer file format
for mapping data that provides a topological structure to describe points,
lines, and polygons. FEMA has adopted the U.S. Geological Survey (USGS)
Digital Line Graph Level 3 optional format for National Flood Insurance
Program mapping and engineer requirements. A DLG may contain lists of
point coordinates describing boundaries, drainage lines, transportation
routes, and other linear features, which are organized by USGS quadrangle
areas. These data are the digital equivalent of the linear hydrographic
and cultural data on a topographic base map. The flood risk thematic layers
developed by FEMA will fit the quadrangle as an overlay.
Digital Line Graph Level 3 (DLG-3)—Data files that
are fully topologically structured and are designed to be integrated into
Geographic Information Systems.
Digital Orthophoto Quadrangle (DOQ)—Photographic
maps distributed by the U.S. Geological Survey. A DOQ is an aerial photograph
that is adjusted to remove distortions caused by variations in terrain
and the camera lens to produce a photograph that displays features in
their planimetrically correct location. This term is sometimes used loosely
to mean any photographic map produced by this process.
Digital Terrain Model (DTM)—A land surface represented
in digital form by an elevation grid or lists of three-dimensional coordinates.
Digitizing—A process of converting an analog image
or map into a digital format usable by a computer.
Disaster Field Office (DFO)—The term used to describe
the office that is the central coordinating point for all response and
recovery efforts by State and Federal agencies as a result of widespread
damage caused by a disaster. The DFO does not directly serve the public,
but functions as a headquarters from which emergency managers operate.
Drawing Exchange File (DXF)—A commonly used format
for the exchange of graphic data.
Edge Matching—The comparison and graphic adjustment
of features to obtain agreement along the edges of adjoining map sheets.
Effective Date—The date on which the National Flood
Insurance Program Map for a community becomes effective and all sanctions
of the National Flood Insurance Program apply.
Effective Map—The National Flood Insurance Program
map issued by FEMA that is in effect as of the date shown in the title
block of the map as “Effective Date,” “Revised,”
or “Map Revised.”
Elevation Reference Mark (ERM) — Temporary vertical
control monument established by a FEMA Study Contractor during the performance
of a study or restudy.
Elevation Reference Point (ERP)—A temporary mark,
the elevation of which is determined by levels or Differential Global
Positioning System positioning from a bench mark or elevation reference
mark. For purposes of the National Flood Insurance Program, ERPs are submitted
with copies of field notes or a documented summary of procedures.
Emergency Phase—The phase of the National Flood
Insurance Program that was implemented, on an emergency basis, to provide
a first-layer amount of insurance on all insurable structures before the
effective date of the initial Flood Insurance Study and Flood Insurance
Rate Map.
Emergency Preparedness and Response Directorate—The
component of the U.S. Department of Homeland Security that, among other
responsibilities, administers the National Flood Insurance Program.
Emergency Program—See Emergency Phase.
Encroachment—Construction, placement of fill, or
similar alteration of topography in the floodplain that reduces the area
available to convey floodwaters.
Engineering Study Data Package (ESDP) Project—A
project designed to maintain archival engineering data and other pertinent
flood hazard data in hardcopy and electronic form and to distribute these
data to interested parties.
Engineering Study Data Package Facility (ESDPF) —The
facility, maintained for FEMA by a contractor, where archival engineering
data and other pertinent flood hazard data, are prepared in final form
ready for distribution to interested parties.
Exporting—The process of transferring digital data
or software from one system to another system.
Existing Data Study (XDS)—This term is used to
describe the process by which FEMA uses previously published flood hazard
information to prepare a Flood Insurance Study report and Flood Insurance
Rate Map for a community that does not have a FIRM using previously published
flood hazard information. This flood hazard information comes from reports
prepared by Federal agencies for purposes other than the National Flood
Insurance Program, such as Flood Hazard Analyses Reports and Floodplain
Information reports; other engineering reports prepared by Federal, State,
or local agencies; or Flood Insurance Study reports and maps issued by
FEMA for adjacent communities (especially previously unincorporated areas
of a county).
Existing Data Restudy (RXDS)—An Existing Data Study
for a community that is already participating in the Regular Phase of
the National Flood Insurance Program without a flood map.
External Data Request (EDR)—A request from a State,
community, or other non-FEMA source for the archived technical and administrative
support data developed and maintained by FEMA for the National Flood Insurance
Program.
Extraterritorial Jurisdiction (ETJ) Limits—Areas
outside of a community's corporate limits where the community has authority
to regulate zoning and issue building permits.
F
Federal Contractors—The five Federal agencies that
conduct flood studies, under contract with FEMA, for the Limited Map Maintenance
Program: U.S. Army Corps of Engineers, U.S. Geological Survey, U.S. Soil
Conversation Service, U.S. Bureau of Reclamation, and Tennessee Valley
Authority.
Federal Emergency Management Agency (FEMA)—The component of the
Emergency Preparedness and Response Directorate within the U.S. Department
of Homeland security that oversees the administration of the National
Flood Insurance Program.
FEMA Levee Inventory System (FLIS)—A Web-based
database and information retrieval system used by FEMA to collect and
maintain information on structures shown on effective and soon-to-be-effective
Flood Insurance Rate Maps, including levees, dikes, floodwalls, and road
and railroad embankments.
Federal Register—The document, published daily by the Federal Government,
that presents regulation changes and legal notices issued by Federal agencies.
FEMA publications in the Federal Register include Proposed, Interim, and
Final Rules for BFE determinations; Compendium of Flood Map Changes published
twice each year; and Final Rules concerning community eligibility for
the sale of flood insurance.
Fee-Charge System Administrator—The individual
that is responsible for processing and maintaining records of payments
submitted to the National Flood Insurance Fund for conditional and final
map change requests and requests for technical and administrative support
data.
FEMA Lead—FEMA staff member (usually the Regional
Project Officer or the Flood Map Production Coordination Contractor Project
Officer at FEMA Headquarters) that oversees project scope, schedule, and
budget, and coordinate the Project-related activities of the various Flood
Hazard Mapping Partners.
Fill—Soil that is brought in to raise the level
of the ground. Depending on where the soil is placed, fill may change
the flow of water or increase flood elevations. Fill may be used to elevate
a building to meet National Flood Insurance Program requirements. Sometimes
fill is combined with other methods of elevation such as pilings or foundation
walls. Placement of fill requires a local permit from the community.
Fiscal Year—The 12-month period that begins on
October 1 and ends on September 30.
Flood—A general and temporary condition of partial
or complete inundation of normally dry land areas from (1) the overflow
of inland or tidal waters or (2) the unusual and rapid accumulation or
runoff of surface waters from any source.
Flood Boundary and Floodway Map (FBFM)—The floodplain
management map issued by FEMA that depicts, based on detailed flood hazard
analyses, the boundaries of the 1-percent-annual-chance (100-year) and
the 0.2-percent-annual-chance (500-year) floodplains and, when appropriate,
the regulatory floodway. The FBFM does not show flood insurance risk zones
or BFEs.
Flood-Control Storage—Storage of water in reservoirs
to abate flood damage.
Flood Elevation Determination Docket (FEDD) — A
file maintained by FEMA that includes all correspondence between FEMA
and the community concerning a flood study; reports of meetings held among
FEMA representatives, community representatives, the State NFIP Coordinator,
private citizens, FEMA and community contractors, or other interested
parties; relevant publications (e.g., newspaper notices, Federal Register
notices); Letter of Final Determination; a copy of the Flood Insurance
Study report; and a copy of the Flood Insurance Rate Map and FBFM.
Floodflow-Frequency Curve—A graph showing the number
of times per year on the average that floods of certain magnitudes are
equaled or exceeded.
Flood Hazard Analyses Report (FHAR) — A flood hazard
report prepared by the Natural Resources Conservation Service (formerly,
the U.S. Soil Conservation Service) for purposes other than the National
Flood Insurance Program.
Flood Hazard Boundary Map (FHBM)—The initial insurance
map issued by FEMA that identifies, based on approximate analyses, the
areas of the 1-percent-annual-chance (100-year) flood hazard within a
community.
Flood Hazard Mapping Program—The program undertaken
by FEMA to conduct FISs and prepare reports and maps delineating flood
hazards in floodprone communities throughout the United States.
Flood Insurance Rate Map (FIRM)—The insurance and
floodplain management map produced by FEMA that identifies, based on detailed
or approximate analyses, the areas subject to flooding during a 1-percent-annual-chance
(100-year) flood event in a community. Flood insurance risk zones, which
are used to compute actuarial flood insurance rates, also are shown. In
areas studied by detailed analyses, the FIRM shows Base Flood Elevations
(BFEs) to reflect the elevations of the 1-percent-annual-chance flood.
For many communities, when detailed analyses are performed, the FIRM also
may show areas inundated by 0.2-percent-annual-chance (500-year) flood
and regulatory floodway areas.
Flood Insurance Rate Zones— See Flood Insurance
Risk Zones.
Flood Insurance Restudy (RFIS)—A revised study
of flood hazards performed for a community that already has an effective
FIRM (and, in some cases, FBFM). An RFIS also may be referred to as a
“Type 19 RFIS” or a “Type 19 restudy.” FEMA Study
Contractors have traditionally performed RFISs. However, communities,
regional agencies, and States that are participating in the Cooperating
Technical Partner initiative also may perform these types of Flood Map
Projects.
Flood Insurance Risk Zones—The zones, also referred
to as “risk premium rate zones” and “flood insurance
rate zones,” shown on a FIRM or FHBM that are used to determine
flood insurance premium rates for properties in the community covered
by the FIRM or FHBM. The flood insurance risk zones include Special Flood
Hazard Areas (i.e., Zones A, A1-30, AE, A0, A99, AH, AR, AR/A, AR/A1-30,
AR/AE, AR/A99, V, V1-30, VE, V0) and areas outside Special Flood Hazard
Areas (i.e., Zones B, X, D, M, N, P, E).
Flood Insurance Study (FIS)—The initial study of
flood hazards performed for a community that does not have an effective
Flood Insurance Rate Map (FIRM) or Flood Boundary and Floodway Map (FBFM).
An FIS also may be referred to as a “Type 15 FIS” or a “Type
15 study.” FEMA Study Contractors have traditionally performed FISs.
However, communities, regional agencies, and States that are participating
in the Cooperating Technical Partners initiative also may perform these
types of Flood Map Projects.
Flood Insurance Study (FIS) Report—A document,
prepared and issued by FEMA, that documents the results of the detailed
flood hazard assessment performed for a community. The primary components
of the FIS report are text, data tables, photographs, and Flood Profiles.
Flood Map Production Coordination Contractor (MCC)—A
private-sector engineering firm that, under contract to FEMA, reviews
and processes new and revised flood studies, appeals and protests related
to the new and revised flood studies, conditional and final map amendments,
conditional and final map revisions, and requests for Letters of Determination
Review; performs activities related to program development and program
support; and maintains regional archives of flood hazard mapping and related
data.
Flood Map Project—Any activity undertaken by FEMA
or a Flood Hazard Mapping Partner to create a new flood map or update
an existing flood map, including detailed studies, approximate studies,
and redelineations of floodplain boundaries based on updated topographic
information.
Floodplain—Any land area that is susceptible to
being inundated by water from any source.
Floodplain Information Report (FPI)—A flood hazard
report prepared by a Federal agency (usually, the U.S. Army Corps of Engineers
or U.S. Geological Survey) for purposes other than the National Flood
Insurance Program.
Floodplain Management—The operation of a program
of corrective and preventative measures for reducing flood damage, including,
but not limited to, emergency preparedness plans, flood-control works,
and floodplain management regulations.
Floodplain Management Regulations—The zoning ordinances,
subdivision regulations, building codes, health regulations, special-purpose
ordinances, and other applications of enforcement used by a community
to manage development in its floodplain areas.
Floodprone Area—See Floodplain.
Floodprone Community—Any community that is subject
to inundation by the base (100-year) flood.
Flood Profile—A graph showing the relationship
of water-surface elevation to location, with the latter generally expressed
as distance above the mouth for a stream of water flowing in an open channel.
Flood Protection System—Those physical works for
which funds have been authorized, appropriated, and expended and which
have been constructed specifically to modify flooding in order to reduce
the extent of the area subject to a “special flood hazard”
and the extent of the depths of the associated flooding. Flood protection
systems typically include hurricane tidal barriers, dams, reservoirs,
levees, or dikes.
Floodway—See Regulatory Floodway.
Floodway Fringe—The portion of the 1-percent-annual-chance
(100-year) floodplain that is not within the regulatory floodway and in
which development and other forms of encroachment may be permitted under
certain circumstances.
Frame—Refers to the size of a FIRM or FBFM panel
as follows: A Frame (28"x21"); B Frame (28"x24");
C Frame (28"x28"); D Frame (28"x32"); E Frame (28"x40").
Freeboard—A factor of safety usually expressed
in feet above a flood level for purposes of floodplain management.
Fully Analytical Aerial Triangulation (FAAT)—A
process for the extension of horizontal and vertical control whereby the
measurements of angles and/or distances on overlapping photographs are
related into a spatial solution using the perspective principles of the
photographs, obtained totally by computational routines.
Future-Conditions Floodplain or Flood Hazard Area—The
land area that would be inundated by the 1-percent-annual-chance (100-year)
flood based on future-conditions hydrology.
Future-Conditions Hydrology—The flood discharges
associated with projected land-use conditions based on a community’s
zoning maps and/or comprehensive land-use plans and without consideration
of projected future construction of flood detention structures or projected
future hydraulic modifications within a stream or other waterway, such
as bridge and culvert construction, fill, and excavation.
G
Geocoding—The process of associating geographic
coordinates or grid cell identifiers to data, points, lines, and shapes.
Geographic Information System (GIS)—A system of
computer hardware, software, and procedures designed to support the capture,
management, manipulation, analysis, modeling, and display of spatially
referenced data for solving complex planning and management problems.
Geographic Resources Analysis and Support System (GRASS)—Geographic
Information System software that was developed by the U.S. Army Corps
of Engineers and is used by several Federal agencies.
Georeference System—An X,Y or X,Y,Z coordinate
system that locates points on the surface of the earth as a reference
to points on a map.
Global Positioning System (GPS)—A satellite-based
navigation and positioning system that enables horizontal and vertical
positions to be determined
Grid—A network of uniformly spaced horizontal and
perpendicular lines that enclose an area with an associated value assigned.
A defined aggregate spatial object.
H
Hazard—An event or physical condition that has
the potential to cause fatalities, injuries, property damage, infrastructure
damage, agricultural loss, damage to the environment, interruption of
business, and other types of loss or harm.
Hazard Mitigation Grant Program (HMGP)—The program,
authorized under Section 404 of the Stafford Act, under which FEMA provides
grants to States and local governments to implement long-term hazard mitigation
measures after a presidential disaster declaration. The purpose of the
HMGP is to reduce the loss of life and property due to natural disasters
and to enable mitigation measures to be implemented during the immediate
recovery from a presidentially declared disaster.
Headquarters (HQ) —The FEMA office in Washington,
DC.
Horizontal Control—A network of stations of known
geographic or grid positions referred to a common horizontal datum, which
control the horizontal positions of mapped features with respect to parallels
and meridians, or northing and easting grid lines shown on the map.
Hydraulic Analysis—An engineering analysis of a
flooding source carried out to provide estimates of the elevations of
floods of selected recurrence intervals.
Hydraulic Computer Model—A computer program that
uses flood discharge values and floodplain characteristic data to simulate
flow conditions and determine flood elevations.
Hydraulic Methodology—Analytical methodology used
for assessing the movement and behavior of floodwaters and determining
flood elevations and regulatory floodway data.
Hydrograph—A graph showing stage, flow, velocity,
or other properties of water with respect to time.
Hydrologic Analysis— An engineering analysis of
a flooding source carried out to establish peak flood discharges and their
frequencies of occurrence.
Hydrology—The science encompassing the behavior
of water as it occurs in the atmosphere, on the surface of the ground,
and underground.
I
Ice Jam—An accumulation of ice in a stream that
reduces the cross-sectional area available to carry streamflow and increases
the water-surface elevation of the stream.
Importing—The process of bringing data or software
into a dissimilar system.
Initializing—The process of setting program variables
to their starting values, commonly zero, at the beginning of a program.
Interior Drainage Systems—Systems associated with
levee systems that usually include storage areas, gravity outlets, pumping
stations, or a combination thereof.
Island—A closed two-dimensional figure. In a GIS,
an island is a unit of land cover lying completely within another land-cover
unit.
K
Kilobyte—A unit of memory representing 1,024 bytes
and often designated with the symbol K, as 4Kb or 4 kilobytes. The symbol
K is also used to refer to 1,024 words of any specified size.
L
Layer—The various "overlays" of data,
each of which normally deals with one thematic topic. The overlays are
registered to each other by the common coordinate system of the database.
In a GIS, a layer or a theme represents a specific kind of data.
Legally Defined Parcel of Land—A parcel of land
for which a metes and bounds description or a plat has been recorded.
Structure may exist on legally defined parcels of land.
Letter of Determination Review (LODR)—A FEMA response
to a request from a borrower and lender that FEMA provide its concurrence
or disagreement with the lender’s determination on whether the borrower’s
building is in the SFHA shown on the effective National Flood Insurance
Program map.
Letter of Final Determination (LFD)—The letter
in which FEMA announces its final determination regarding the flood hazard
information, including (when appropriate) proposed and proposed modified
BFEs, presented on a new or revised FIRM, FIS report, and (when appropriate)
FBFM for a particular community. In the LFD, FEMA begins the compliance
period and establishes the effective date for the new or revised FIRM,
FIS report, and/or
Letter of Map Amendment (LOMA) —An official determination
by FEMA that a property has been inadvertently included in an SFHA as
shown on an effective FHBM or FIRM and is not subject to inundation by
the 1-percent-annual-chance flood. Generally, the property is located
on natural high ground at or above the BFE or on fill placed prior to
the effective date of the first National Flood Insurance Program map designating
the property as within an SFHA. Limitations of map scale and development
of topographic data more accurately reflecting the existing ground elevations
at the time the maps were prepared are the two most common bases for LOMA
requests.
Letter of Map Change—A collective term used to
describe official amendments and revisions to National Flood Insurance
maps that are accomplished by a cost-effective administrative procedure
and disseminated by letter.
Letter of Map Change Revalidation (LOMC-VALID) Letter—A letter issued
by FEMA, immediately before the effective date of a revised FIRM, to notify
community officials about LOMAs, LOMR-Fs, and LOMRs that will remain in
effect after the FIRM is published.
Letter of Map Revision (LOMR)—A letter issued by
FEMA to revise the FIRM, FBFM, and/or FIS report for a community to change
in BFEs, floodplain and floodway boundary delineations, and coastal high
hazard areas.
Letter of Map Revision Based on Fill (LOMR-F)—A
Letter of Map Change issued by FEMA when FEMA determines that a legally
defined parcel of land or structure has been elevated above the BFE based
on the placement of earthen fill after the date of the first National
Flood Insurance Program map.
Levee—A manmade structure, usually an earthen embankment,
designed and constructed in accordance with sound engineering practices
to contain, control, or divert the flow of water so as to provide protection
from temporary flooding.
Light Detection and Ranging (LIDAR) System—An airborne
laser system, flown aboard rotary or fixed-wing aircraft, that is used
to acquire x, y, and z coordinates of terrain and terrain features that
are both manmade and naturally occurring. LIDAR systems consist of an
airborne Global Positioning System with attendant base station(s), Inertial
Measuring Unit, and light-emitting scanning laser.
Limited Map Maintenance Program Project Revision (LMMP)—A
limited-scope restudy of flood hazards that generally involves a single
community and one watercourse. The data submitted to FEMA by the SC for
an LMMP are similar in format and level of detail to those submitted for
an RFIS.
Line—A level of spatial measurement referring to
a one-dimensional defined object having a length, direction, and connecting
at least two points.
Local Newspaper—The community newspaper, identified
by the CEO or other designated community official, in which FEMA publishes
notices at the beginning of a Flood Map Project, at the beginning of the
appeal period, and at other times during the processing of a new or revised
FIRM when required.
Lot—A parcel of land for which a metes and bounds
description or a plat has been recorded and on which one or more structures
may be built.
Lowest Adjacent Grade (LAG)—The lowest natural
elevation of the ground surface next to a structure.
Lowest Finished Floor Elevation (LFFE)—The lowest
floor of the lowest enclosed area (including basement) of a structure.
M
Manning’s n—A coefficient of roughness, used
in a formula for estimating the capacity of channel to convey water.
Manufactured Home—Any building that is transportable
in one or more sections, which is built on a permanent chassis and designed
to be used with or without a permanent foundation when connected to the
required utilities. Park trailers, recreational vehicles, and other similar
vehicles are not considered manufactured homes.
Map Amendment—A change to an effective National
Flood Insurance Program map that results in the exclusion from the Special
Flood Hazard Area of an individual structure or legally defined parcel
of land that has been inadvertently included in the Special Flood Hazard
Area (i.e., no alterations of topography have occurred since the date
of the first National Flood Insurance Program map that showed the structure
or parcel to be within the Special Flood Hazard Area.
Map Assistance Center—A FEMA customer service center
staffed by Map Specialists that are specially trained to answer specific
questions about the status of active and completed studies, restudies,
conditional and final map revision requests, and conditional and final
map amendment requests; answer questions about technical and administrative
support data available from the FEMA archives; link callers with other
FEMA service and fax numbers and the FEMA website; and provide information
regarding, or copies of, FEMA products, brochures, and publications.
Map Needs Update Support System (MNUSS)—The computerized
database system that is used by FEMA and its Flood Hazard Mapping Partners
to compile information on mapping needs nationwide collected using the
Mapping Needs Assessment Process.
Mapping Activity Statement (MAS)—An agreement signed
by FEMA and a participant (community, regional agency, or State agency)
in the CTP initiative under which the participant will complete specific
mapping activities.
Mapping Needs Assessment Process (MNAP)—The process
by which FEMA identifies mapping needs nationwide by contacting States,
regional agencies, and mapped participating communities for information;
verifies the validity of the identified needs; and compiles information
on those needs into a computerized database.
Map Revision—A change to an effective National
Flood Insurance Program map that is accomplished by a LOMR or a Physical
Map Revision.
Memorandum of Agreement—See Partnership Agreement.
Minimally Floodprone Community—A community that
FEMA has determined to be subject to inundation by the 1-percent-annual-chance
(100-year) flood, but for which existing conditions indicate that the
area is unlikely to be developed in the foreseeable future. The criteria
used by FEMA to evaluate a community’s development potential are
as follows: (1) Floodplains are publicly owned and designed for open space
or preservation; (2) Zoning laws, sanitary codes, subdivision regulations,
shore land regulations, or community regulations effectively prohibit
floodplain development; (3) Surrounding land use or topography effectively
limits the development potential; (4) Population is decreasing or stable,
and there is no foreseeable pressure for floodplain development; and (5)
Floodplains are remote and uninhabited, and future development is unlikely.
Mitigation—A sustained action taken to reduce or
eliminate long-term risk to people and property from flood hazards and
their effects. Mitigation distinguishes actions that have a long-term
impact from those are more closely associated with preparedness for, immediate
response to, and short-term recovery from specific events.
N
National Flood Insurance Fund (NFIF) —The fund
used as the funding mechanism for the National Flood Insurance Program.
National Flood Insurance Program (NFIP) — Federal
Program under which flood-prone areas are identified and flood insurance
is made available to the owners of the property in participating communities.
Network Analysis—Analytical technique concerned
with the relationships between locations on a network, such as the calculation
of optimal routes through road networks, capacities of network systems,
best locations for facilities along networks.
Node—A point at which two or more lines meet; called
an edge or vertex in graph theory.
Non-Floodprone Community—A community that FEMA
has determined not to be subject to inundation by the 1-percent-annual-chance
(100-year) flood. The FEMA guidelines employed for determining whether
a community is designated as non-floodprone are that all of its SFHAs
are less than 200 feet wide and all drain less than 1 square mile, or
physiographic features that preclude floodplain development exist in the
community.
Non-Participating Community—A community that has
been identified by FEMA as being floodprone but has chosen not to participate
in the National Flood Insurance Program.
Notice-To-User Revision—A revision made by FEMA
to correct a non-technical problem with a published FIS Report, FIRM,
or FBFM quickly and inexpensively. These types of revisions are intended
solely to correct a noted defect with the product and cannot be used to
establish new or revised flood hazard information.
O
Operating System—The master control program that
governs the operation of a computer system, running job entry, input/output
services, data management, and supervision or housekeeping.
Otherwise Protected Area (OPA)—An undeveloped coastal
barrier within the boundaries of an area established under Federal, State,
or local law, or held by a qualified organization, primarily for wildlife
refuge, sanctuary, recreational, or natural resource conservation purposes.
P
Participating Community—Any community that voluntarily
elects to participate in the National Flood Insurance Program by adopting
and enforcing floodplain management regulations that are consistent with
the standards of the National Flood Insurance Program.
Partnership Agreement—An agreement, also referred
to as a Memorandum of Agreement, that is signed by FEMA and a community,
regional agency, or State agency that wishes to participate in the Cooperating
Technical Partners initiative. The Partnership Agreement is a broad statement
of principle, emphasizing the value of the National Flood Insurance Program's
three components of insurance, floodplain management, and mapping.
Permanent Identifier (PID)—The six-character alphanumeric
code used by the National Geodetic Survey to identify control points and
stations.
Physical Map Revision (PMR)—A revision made by
FEMA to a FIRM, FBFM, or FIS report based on community-supplied data.
FEMA issues PMRs when (1) changes resulting from the requested revision
are extensive, affecting significant portions of a FIRM panel or multiple
FIRM panels; (2) revision will add significant SFHAs to the effective
FIRM; or (3) revision will result in an increase in the BFEs and/or regulatory
floodway.
Pixel—The smallest discrete element that makes
up a digital image. (Short for "picture element".)
Planimetric Map—A map representing only horizontal
positions from features represented; distinguished from a topographic
map by the omission of relief in measurable form. A planimetrically accurate
map shows accurate horizontal distances between features.
Point—A level of spatial measurement that refers
to an object that has no dimension.
Point Data—In a vector structure, the data that
consist of a single, distinct X,Y coordinate. In a raster structure, the
data that consist of single cells.
Polygon—A two-dimensional figure with three or
more sides intersecting at a like number of points. (In GIS, a polygon
is an area.)
Ponding—The result of runoff or flows collecting
in a depression that may have no outlet, subterranean outlets, rim outlets,
or manmade outlets such as culverts or pumping stations. Impoundments
behind manmade obstructions are included in this type of shallow flooding
as long as they are not backwater from a defined channel or do not exceed
3.0 feet in depth.
Position Dilution of Precision (PDOP)—In a study
area, an indicator of the positional accuracy that can be derived from
the current Global Positioning System satellite geometry, which varies
continuously; the smaller the PDOP number, the higher the data quality.
Primary Airport Control (PAC) Stations—The geodetic
control station that provides the reference frame for the positioning
of all critical features on an airport.
Primary Frontal Dune—A 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.
Probability Density Function (PDF)—A distribution
of probability for a continuous random variable.
Project Officer (PO)—A FEMA Headquarters staff
member who performs contract monitoring functions, which include providing
technical direction to FEMA contractors, monitoring the progress of contractors’
work, and evaluating contractor performance.
Proposed Base Flood Elevations/Depths and Proposed Modified Base
Flood Elevations/Depths—Those Base Flood Elevations and
base flood depths that FEMA publishes in a local newspaper and in the
Federal Register at the start of the 90-day appeal period.
Protest—An objection to any information, other
than BFEs, shown on an NFIP map that is submitted by community officials
or interested citizens through the community officials during the 90-day
appeal period.
Q
Q3 Flood Data Product—A digital representation
of certain features of the FIRM that is intended for use with desktop
mapping and Geographic Information System technology. The Q3 Flood Data
product is created by scanning the effective FIRM paper maps and digitizing
selected features and lines.
Quadrangle—A U.S. Geological Survey (USGS) topographic
map;
Quality Assurance/Quality Control (QA/QC) Reviews—The
reviews of the Flood Insurance Study reports, maps, and related products
and data performed to ensure compliance with FEMA standards.
R
Raster—The pattern of horizontal, parallel scan
lines comprising the image on a CRT screen, on which each scan line consists
of segments varying in intensity.
Record—A group of items in a file treated as a
unit.
Recurrence Interval—The average interval of time
within which a given flood will be equaled or exceeded once.
Regional Offices (ROs)—The FEMA offices located
in Boston, Massachusetts; New York, New York; Philadelphia, Pennsylvania;
Atlanta, Georgia; Chicago, Illinois; Denton, Texas; Kansas City, Missouri;
Denver, Colorado; San Francisco, California; and Bothell, Washington.
Regional Project Officer (RPO)—A FEMA Regional
Office staff member in the who performs contract monitoring functions,
which include providing technical direction to FEMA contractors, monitoring
the progress of contractors’ work, and evaluating contractor performance.
Regression Equation—An experimentally determinable
equation of a regression curve; that is, an approximate, generally linear
relation connecting two or more quantities and derived from the correlation
coefficient.
Regular Phase—The phase of a community’s
participation in the National Flood Insurance Program when more comprehensive
floodplain management requirements are imposed and higher amounts of insurance
are available. The FIRM forms the basis for this phase of participation
in the National Flood Insurance Program.
Regular Program—See Regular Phase.
Regulatory Floodway—A floodplain management tool
that is the regulatory area defined as the channel of a stream, plus any
adjacent floodplain areas, that must be kept free of encroachment so that
the base flood discharge can be conveyed without increasing the BFEs more
than a specified amount. The regulatory floodway is not an insurance rating
factor.
Riverine Flooding—The overbank flooding of rivers
and streams.
River Mile Marker (RMM) —A marker that indicates
the distance in miles from a reference point on a river or other major
watercourse.
Root Mean Square Error (RMSE) —The square root
of the average of the set of squared differences between dataset coordinate
values and coordinate values from an independent source of higher accuracy
for identical points RMSE is used to estimate both horizontal and vertical
accuracy.
S
Scale—A representative fraction of a paper map
distance to ground distance.
Scanner—Any device that systematically decomposes
a sensed image or scene into pixels and then records some attribute of
each pixel.
Scanning—The process of using an electronic input
device to convert analog information into a digital format usable by a
computer.
Secondary Airport Control (SAC) Stations—The geodetic
control stations that, together with the PAC Station, provide the reference
frame for the positioning of all critical features on an airport.
Sediment—Fragmental material that originates from
the weathering of rocks and is transported by, suspended in, or deposited
by water or air or is accumulated in beds by other natural occurrence.
Scientifically Incorrect Base Flood Elevations—Those
Base Flood Elevations determined through analyses in which the methodologies
used and/or assumptions made are inappropriate for the physical processes
being evaluated or are otherwise erroneous.
Shallow Flooding— Unconfined flows over broad,
relatively low relief areas, such as alluvial plains; intermittent flows
in arid regions that have not developed a system of well-defined channels;
overbank flows that remain unconfined, such as on delta formations; overland
flow in urban areas; and flows collecting in depressions to form ponding
areas. For National Flood Insurance Program purposes, shallow flooding
conditions are defined as flooding that is limited to 3.0 feet or less
in depth where no defined channel exists.
Sheet Runoff—The broad, relatively unconfined downslope
movement of water across sloping terrain that results from many sources,
including intense rainfall and/or snowmelt, overflow from a channel that
crosses a drainage divide, and overflow from a perched channel onto deltas
or plains of lower elevation. Sheet runoff is typical in areas of low
topographic relief and poorly established drainage systems.
Special Conversion—An action taken by FEMA to convert
a community to the Regular Phase of the National Flood Insurance Program
without preparing a FIRM with detailed flood risk zones. The exact action
taken depends on whether FEMA determines the community is “non-floodprone”
or “minimally floodprone.”
Special Conversion Recommendation Report (SCRR) —A
report, prepared by the FEMA Regional Office and submitted to FEMA HQ,
that documents the reasons a community should be converted to the Regular
Phase of the National Flood Insurance Program without a detailed engineering
study being performed and recommends a specific conversion action.
Special Flood Hazard Area (SFHA)—The area delineated
on a National Flood Insurance Program map as being subject to inundation
by the base flood. SFHAs are determined using statistical analyses of
records of riverflow, storm tides, and rainfall; information obtained
through consultation with a community; floodplain topographic surveys;
and hydrologic and hydraulic analyses.
Special Problem Report (SPR) —A report, prepared
by the Flood Hazard Mapping Partner that is performing an engineering
study or other mapping activity, that documents special problems or issues
encountered during the performance of the work.
Stage—The height of a water surface above an established
datum plane.
Standard Interchange Format (SIF)—-A commonly used
format for the exchange of alphanumeric data.
State—Any State, the District of Columbia, the
territories and possessions of the United States, the Commonwealth of
Puerto Rico, and the Trust Territory of the Pacific Islands.
State Coordinating Agency— See State National Flood
Insurance Program Coordinator.
State National Flood Insurance Program (NFIP) Coordinator—The agency
of the State government, or other office designated by the Governor of
the State or by State statute at the request of FEMA to assist in the
implementation of the National Flood Insurance Program in that state.
State Plane Coordinates—A system of X,Y coordinates
defined by the U.S. Geological Survey for each state. Locations are based
on the distance from an origin within each state.
Stillwater Flood Elevation (SWEL)—Projected elevation
that flood waters would assume, referenced to National Geodetic Vertical
Datum of 1929, North American Vertical Datum of 1988, or other datum,
in the absence of waves resulting from wind or seismic effects.
Stillwater Flood Level (SWFL)—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—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 flood
insurance purposes, a walled and roofed building, other than a gas or
liquid storage tank, that is principally above ground and affixed to a
permanent site, as well as a manufactured home on a permanent foundation.
Study Contractor (SC)—An architectural and engineering
firm or a Federal, State, or local agency that performs flood hazard studies
under contract with FEMA.
Subcritical Flow—Flow with a mean velocity that
is less than the critical velocity; in other words, tranquil flow.
Summary of Map Actions (SOMA)—A list, generated
by FEMA and delivered to the community that summarizes the LOMAs, LOMR-Fs,
and LOMRs that are or will be affected by a physical update to a FIRM.
Supercritical Flow—Flow with a mean velocity that
is greater than the critical velocity; in other words, rapid flow.
T
Tagged Information File Format (TIFF)—The technical
exchange format for raster or image files.
Technical Evaluation Contractor (TEC)—See Flood
Map Production Coordination Contractor.
Technical Support Data Notebook (TSDN)—The format
for the FEMA-maintained file that contains all of the technical and administrative
support data for a community for which FEMA published an National Flood
Insurance Program map and all revisions to that map.
Technically Incorrect Base Flood Elevations (BFEs)/Depths—Those
BFEs and base flood depths determined through analyses in which the methodologies
used have not been applied properly, are based on insufficient or poor-quality
data, or do not account for the effects of physical changes that have
occurred in the floodplain.
Temporary Bench Mark (TBM)—Benchmark established
for a particular Flood Map Project or community.
Topologically Integrated Geographic Encoding and Referencing System (TIGER)—The
nationwide digital database of planimetric base map features developed
by the U.S. Bureau of the Census for the 1990 Census.
Topology—A branch of geometric mathematics that
is concerned with order, continuity, and relative position, rather than
actual linear dimensions.
Transect—Cross section taken perpendicular to the
shoreline to represent a segment of coast with similar characteristics
Transformation—The conversion of coordinates between
alternative referencing systems.
Triangulated Irregular Network (TIN)—A set of non-overlapping
triangles developed from irregularly spaced points that are used to represent
the facets of a surface.
U
Undeveloped Coastal Barrier—Any land area adjacent
to the Atlantic Ocean, Pacific Ocean, or Great Lakes, where flood insurance
will not be available for new or substantially improved structures. These
areas are protected by law to discourage development in an attempt to
preserve dunes, beaches, and wildlife habitats.
Unit Hydrograph—The hydrograph of direct runoff
from a storm uniformly distributed over a drainage basin during a specified
unit of time.
Universal Transverse Mercator (UTM) Grid—A system
of plane coordinates based on 60 north-south trending zones, each 16 degrees
of longitude wide, that circle the globe.
Unnumbered A Zones—Flood insurance rate zones,
designated “Zone A” on a FIRM, that are based on approximate
studies.
V
Vector—A directed line segment with magnitude commonly
represented by the coordinates for the pair of endpoints.
Vector Data—Data in the form of an array with one
dimension.
Vector Product Format (VPF)—A standard format,
structure, and organization, used by the National Imagery and Mapping
Agency, for large geographic databases that are based on a georelational
data model and are intended for direct use. VPF is designed to be compatible
with a wide variety of applications and products. VPF uses tables and
indexes that permit direct access by spatial location and thematic content
and is designed to be used with any digital geographic data in vector
format that can be represented using nodes, edges, and faces. VPF defines
the format of data objects, and the georelational data model provides
a data organization within which software can manipulate the VPF data
objects.
Velocity Zone—See Coastal High Hazard Area.
Violation—The failure of a structure or other development
to be fully compliant with a community’s floodplain management regulations.
A structure or other development without an Elevation Certificate, other
certifications, or other evidence of compliance required in Section 60.3
of the National Flood Insurance Program regulations is presumed to be
in violation until such time as that documentation is provided.
W
Watershed—An area of land that drains into a single
outlet and is separated from other drainage basins by a divide.
Water-Surface Elevations (WSELs)—The heights of
floods of various magnitudes and frequencies in the floodplains of coastal
or riverine areas, in relation to a specified vertical datum.
Wave Height—Vertical distance between the wave
crest and the wave trough.
Wave Runup—Rush of wave water up a slope or structure.
Wave Setup—The Increase in the still water surface
near the shoreline, due to the presence of breaking waves.
Work Map—Floodplain mapping submitted to FEMA by
a Mapping Partner, reflecting the results of a flood study or other mapping
activity. The work map depicts floodplain boundaries, regulatory floodway
boundaries, BFEs, and cross sections, and provides the basis for the presentation
of this information on a FIRM.
Z
Zone Gutter—Boundary, shown on a FIRM, dividing
SFHAs of different BFEs, base flood depths, flow velocities, or flood
insurance risk zone designations.
Earth Data Analysis Center
MSC01 1110
1 University of New Mexico
Albuquerque, NM 87131-0001