Base Map – Map of the community that depicts cultural features (roads, railroad, bridges, dams, culverts, etc.), drainage features, and the corporate limits.
Buffer Zone – An area of specified distance (radius) around a map item or items.
Coastal Barrier Resources Act (COBRA) – An act of Congress, signed into law in 1982 and amended in 1990 and later, that identifies units of land consisting of undeveloped coastal barriers and other areas located on the coast of the U.S. Flood insurance is not available for structures built after the coastal barrier was identified.
Community Identification (CID) – A unique six-digit number assigned to each community by FEMA and used for identity in computer databases; it is shown on the FIS, FIRM, and in the Q3 Flood Data files. The first two digits of the number are always the State FIPS code.
Community Rating System (CRS) – A program created by FEMA to provide new incentive for activities that reduce flood losses and support the sale of flood insurance. Any community participating in the NFIP may apply for CRS classification by demonstrating that it is implementing floodplain management and public information activities that exceed the minimum requirements of the NFIP. Once qualified, the community benefits by obtaining flood insurance premium rate credits for its residents. The credits vary by the level of activities undertaken by the community.
Digital Flood Insurance Rate Map – (DFIRM) – The Digital Flood Insurance Rate Map (DFIRM) is comprised of all digital data required to create the hardcopy FIRM. This includes base map information, graphics, text, shading, and other geographic and graphic data required to create the final hardcopy FIRM product to FEMA standards and specifications. These data serve the purpose of map design and provides the database from which the Digital Line Graph thematic product of the flood risks can be extracted to create the DFIRM-DLG. These products are generally produced in a countywide format. DFIRMs are subjected to community review and approval and are, therefore, the official basis for implementing the regulations and requirements of the NFIP within the community.
Digital Flood Insurance Rate Map – DLG (DFIRM-DLG) – This product is 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, as described in the FEMA specifications for digital FIRMs. The DFIRM-DLG does not include base map information, nor does it include graphic data required to create a hardcopy FIRM. This product is intended to be the primary means of transferring flood risk data depicted by FIRMs to GISs through a public domain data exchange format. The DFIRM-DLGs are tiled to the U.S. Geological Survey 1:24,000 scale topographic map series.
Digital Line Graph (DLG) – A computer file format for mapping data that provides a topological structure to describe points, lines and polygons. A DLG may contain lists of point coordinates describing boundaries, drainage lines, and other linear or area 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. The U.S. Geological Survey Digital Line Graph Level 3 Optional format has been adopted by FEMA for the purposes of the National Flood Insurance Program mapping and engineer requirements. Level 3 data files are fully topologically structured and are designed to be integrated into GIS.
Elevation Reference Mark (ERM) – A point of vertical ground elevation reference shown on the FIRM for comparison to the BFE. ERMs are referenced to the National Geodetic Vertical Datum (NGVD) or the North American Vertical Datum (NAVD) or an alternative local datum if applicable.
Federal Emergency Management Agency (FEMA) – The agency reporting directly to the President and responsible for identifying and mitigating natural and man-made hazards.
Federal Geographic Data Committee (FGDC) – An interagency committee, established by the Office of Management and Budget, that promotes the coordinated development, use, sharing, and dissemination of geospatial data on a national basis. The FGDC is composed of representatives from 14 Cabinet level and independent Federal agencies.
Federal Information Processing Standards (FIPS) – The official source within the Federal government for information processing standards, which are developed and published by the Institute for Computer Sciences and Technology at the National Institute of Standards and Technology (NIST).
Flood Insurance Rate Map (FIRM) – A map on which the 100- and 500-year floodplains, BFEs, and risk premium zones are delineated to enable insurance agents to issue accurate flood insurance policies to homeowners in communities participating in the NFIP.
Flood Insurance Study (FIS) – An examination, evaluation, and determination of the flood hazards, and if appropriate, the corresponding water-surface elevations.
National Flood Insurance Program (NFIP) – The Federal regulatory program under which flood-prone areas are identified and flood insurance is made available to residents of participating communities.
Quality Assurance/Quality Control (QA/QC) – Intermediate and final review of the FIS and FIRM performed to ensure compliance with FEMA standards.
Q3 Flood Data – A digital FIRM product developed and distributed by FEMA. Q3 Flood Data are developed by scanning and vectorizing the existing hardcopy FIRM to create a raster product suitable for viewing or printing, as well as a thematic vector overlay of flood risks. Q3 Flood Data capture all FIRM data in the raster file, but vectorize only certain features.
Special Flood Hazard Area (SFHA) – Any area inundated by the base (1% annual chance) flood; these areas are identified on the FIRM as Zones A, AE, AH, AO, AR, A1-30, A99, V, VE, and V1-30.
Glossary of mapping terms
Information contained within these flooding pages has generally been excerpted from Federal Emergency Management Agency, Q3 Flood Data Specifications, Draft June 1995, Federal Emergency Management Agency, Washington, D.C.