FEMA Digital Q3 Flood Data

Digital Q3 Flood Data are developed by scanning the existing FIRM hardcopy,
vectorizing a thematic overlay of flood risks. Vector Q3 Flood Data files
contain only certain features from the existing FIRM hardcopy. Q3 vector data
are contained in one single countywide file, including all incorporated and
unincorporated areas of a county.

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

Digital Q3 Flood Data are not tied to a base map, are not used to produce a new
version of the FIRM hardcopy, and are not subjected to community review. The
digital Q3 Flood Data are designed to provide guidance and a general proximity
of the location of Special Flood Hazard Areas.

The digital Q3 Flood Data product can be a valuable tool in screening property
addresses within a Geographic Information System to determine flood risks.
However, since the geographic processing performed to develop digital Q3 Flood
Data may introduce differences with the FIRM hardcopy source, users must apply
considerable care and judgment in the application of this product. For
instance, digital Q3 Flood Data may be overlaid on highly detailed large-scale
community base mapping data, but, if parcel level determinations are made, they
must be prefaced with information about the accuracy of the data from which
they are derived.

Contents of Q3 Data

The vectorized features contained in digital Q3 Flood Data files include:

- Annual chance floodplain areas of 1 and 0.2 percent, including Zone V areas,
certain floodway areas, and zone designations
- Political areas, including community identification numbers
- FIRM panel areas, including panel number and suffix
- 7.5-minute quadrangle areas
- Mapable Letters of Map Change (LOMCs)

[Summary provided by FEMA]