Q3 SPECIAL FLOOD HAZARD AREA (SFHA) SYMBOL DESCRIPTIONS
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100-YEAR FLOOD (BFEs) |
An area inundated by 100-year flooding, for which BFEs (Base Flood Elevations) have been determined. |
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100-YEAR FLOOD (no BFEs) |
An area inundated by 100-year flooding, for which no BFEs have been determined. |
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100-YEAR FLOOD (sheet flow) |
An area inundated by 100-year flooding (usually sheet flow on sloping terrain), for which average depths have been determined; flood depths range from 1 to 3 feet. |
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100-YEAR FLOOD (ponding) |
An area inundated by 100-year flooding (usually an area of ponding), for which BFEs have been determined; flood depths range from 1 to 3 feet. |
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500-YEAR FLOOD or LEVEE-PROTECTED 100-YEAR FLOOD |
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. |
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FLOODWAY |
An area that includes the channel of a river or other watercourse and the adjacent land areas that must be reserved in order to discharge the base flood without cumulatively increasing the water-surface elevation by more than a designated height. |
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OUTSIDE FLOODPLAIN |
An area that is determined to be outside the 100- and 500-year floodplains. |
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The Federal Emergency Management Agency (FEMA) administers the National Flood Insurance Program (NFIP)
which is mandated to identify floodplain areas and establish Flood Risk Zones.
These zones are identified on Flood Insurance Rate Maps (FIRM) which provide
the basis for floodplain management.
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The Q3 Flood Data product is a digital representation of certain features
of FEMA's FIRM product, intended for use with desk-top mapping and GIS technology.
It is designed to serve FEMA's needs for disaster response activities,
National Flood Insurance Program activities, risk assessment, and floodplain management.
The data is expected to be used for a variety of planning applications including
broad-based review for floodplain management, land-use planning, commercial siting analysis,
insurance target marketing, natural resource/environmental analyses, and real estate development
and targeting. As it does not provide flood elevation information it is limited to providing
users with data to determine whether features are within or outside the Special Flood Hazard Area (SFHA)
to a 250 ft. resolution. The Q3 Flood Data cannot be used to determine absolute delineations of
flood risk boundaries, but instead should be seen as portraying zones of uncertainty and
possible risks associated with flood inundation.
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More information about Q3 data and other FEMA products is available
from The National Flood
Insurance Program (NFIP) Web Site
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