Designed to support FEMA's Response and Recovery activities and flood insurance policy marketing initiatives, Q3 Flood Data are typically used in floodplain management, hazard analysis, and risk assessment. The product contains a subset of information derived from paper Flood Insurance Rate Maps (FIRM data). Read on for more about FIRM and Q3 data

The Q3 Flood Data are developed by scanning the existing hardcopy FIRM to create a raster product suitable for viewing or printing and vectorizing a thematic overlay of flood risks.  Q3 Raster FIRM files contain all FIRM data in raster format, but only certain features are contained in the vector Q3 Flood Data files.

The features contained in the vector Q3 Flood Data files include the following:

• 1% and 0.2% annual chance floodplain areas, including Zone V areas, certain floodway areas, and zone designations;
• Coastal Barrier Resources Act (COBRA) areas;
• political areas, including community identification number;
• FIRM panel areas, including panel number and suffix;
• 7.5-minute quadrangle areas; and
• mappable Letters of Map Change (LOMCs). 

The vector Q3 Flood Data are contained in one single countywide file, including all incorporated and unincorporated areas of a county.  The feature items and attributes are defined in detail in the Q3 Flood Data Specifications

The means for linking other associated NFIP data to these files can be derived from the attributes contained within the files.  For instance, the currently effective FIRM panel from FEMA's Community Status Book or the Flood Map Status Information System (FMSIS) can be compared to the FIRM panel information in the Q3 Flood Data files to determine if the Q3 Flood Data files reflect the most current mapping.

Image Source: FEMA

Metadata

Each Q3 Flood Data file is accompanied by a metadata file that meets the Federal Geographic Data Committee's guidelines for metadata as contained in the Content Standards for Digital Geospatial Metadata.  The metadata files are ASCII text files that describe the contents of and sources used for each Q3 Flood Data file.  The metadata files may be accessed by users to determine if the vector or raster files meet their needs.  In addition, the metadata file provides information specific to the county, including the FIRMs and LOMCs that were digitized.

The horizontal control of Q3 Flood Data vector data is consistent with that required for mapping at the scale of 1:24,000.

Data Sources

The Q3 Flood Data files may have been derived from DFIRM-DLGs, from FIRM-DLGs, or from FIRMs digitized previously for emergency applications, or they may be newly created files.  Q3 Flood Data derived from previously created files may not contain certain items or may contain items that have been captured differently from the current Q3 Flood Data specifications.  Items that may not be included in selected Q3 Flood Data files include the following:

• floodways
• COBRA boundaries
• gutters (or zone breaks)
• 0.2% annual chance floodplains
• FIRM panel neatlines for unprinted panels
• FIRM panel type attributes

The vector Q3 Flood Data files do NOT include the following:

• base map data (streets, etc.)
• base flood elevation lines and elevations
• cross sections and letter identifiers
• elevation reference marks and their elevations
• floodways if not shown on the FIRM

FEMA distributes digital FIRM data in two basic product levels.  These are the DFIRM (including the hardcopy DFIRM and the DFIRM-DLG) and the Q3 Flood Data.

The 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.
This product serves the purpose of map design and provides the database from which the Digital Line Graph (DLG) thematic product of the flood risks is extracted to create the DFIRM-DLG.  This product is 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.

Specifications for digitizing DFIRMs are consistent with those required for mapping at a scale of 1:24,000, or larger.

Raster files

The Q3 Raster FIRMs are black and white scanned images collected at 400 dots per inch from mylar negatives.   The raster files are not georeferenced.  Letters of Map Change are not scanned.

Q3 Flood Data 

The Q3 Flood Data do not replace the existing hardcopy FIRM or, if one exists, DFIRM product.  The product has been designed to support planning activities, some Community Rating System (CRS) activities, insurance marketing, and mortgage portfolio review.  It does not provide base flood elevation information; thus, it has limited application for engineering analysis, particularly for site design or rating of flood insurance policies for properties located within SFHAs.

Q3 Flood Data products are provided in a public domain data transfer format (DLG and Tagged Image File Format or TIFF) as well as proprietary formats (ARC/INFO and MapInfo).

Zone Descriptions attributed with Q3 data

• A An area inundated by 100-year flooding, for which no base flood elevations have been determined.
• AE An area inundated by 100-year flooding, for which base flood elevations have been determined.
• AH An area inundated by 100-year flooding, (usually areas of ponding), for which base flood elevations have been determined. Flood depths range from 1 to 3 feet.
• AO An alluvial fan inundated by 100-year flooding (usually sheet flow on sloping terrain), for which average flood depths and velocities have been determined; flood depths range from 1 to 3 feet.
• D An area of undetermined but possible flood hazards.
• V An area inundated by 100-year flooding with velocity hazard (wave action); no base flood elevations have been determined.
• VE An area inundated by 100-year flooding with velocity hazard (wave action); base flood elevations have been determined.
• FW Floodway areas in Zone AE.
• X-500 An area inundated by 500-year flooding; an area inundated by 100-year flooding with average depths of less than 1 foot or with drainage areas less than 1 square mile; or an area protected by levees from 100-year flooding.
• COBRA_IN Undeveloped coastal barriers which are normally located within or adjacent to special flood hazard areas.

Ordering

The Q3 Flood Data will be distributed through FEMA's Internet server and on CD-ROM as the files become available.  Updates are generally made available bi-annually.

Internet users may download data, along with associated data standards and metadata files by accessing FEMA's Map Service Center through FEMA's World Wide Web site at http://www.fema.gov.  Approximate download times based on file sizes will be included at
this site.  Note: FEMA's Community Status Book is also available to Internet users through FEMA's Web site.

CD-ROMs containing the Q3 Flood Data files may be ordered from FEMA's Map Service Center:

Map Service Center
6730 Santa Barbara Court
Baltimore, Maryland  21227-5832
Telephone: 1-800-358-9616

Suggested Links:

User guide - http://www.msc.fema.gov/nuser_gd.doc

The new DFIRM Viewer is now available. This online GIS application will be continuously updated with DFIRM digital mapping data as the MSC receives it. See also http://gis.msc.fema.gov/Website/DFIRM_Viewer/Viewer.htm

Digital Q3 Flood Data Availability -- States list http://msc.fema.gov/states.shtml