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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)
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