See Also this Flood mapping FAQ from FEMA

Click Here to view a sample graphic showing Q3 data using ArcView GIS for a typical Quad (Okaloosa County, FL in this example)

Q3 FLOOD DATA

 

In its continuing efforts to perform hazards mitigation and to improve

customer service by expanding the availability of flood risk data, the

Federal Emergency Management Agency (FEMA) has released the Q3 Flood Data

product.  Designed to support FEMA's Response and Recovery activities and

flood insurance policy marketing initiatives, Q3 Flood Data will be used

in floodplain management, hazards analysis, and risk assessment activities.

The product contains a subset of information derived from paper Flood

Insurance Rate Maps (FIRMs).  While the digital data were developed to

support floodplain management activities, they do not replace the paper FIRMs.

 

 

DATA DESCRIPTION:

 

The Q3 Flood Data are developed by electronically scanning the current

effective map panels of existing paper FIRMs.  Certain key features are

digitally captured and then converted into area features (floodplain boundaries,

flood insurance zones, political boundaries).  Using computer mapping software,

you can overlay the Q3 Flood Data with your own information (land parcels,

transportation networks, customer addresses, etc.) to display zones of potential

flood risk and identify future marketing opportunities.

 

Q3 Flood Data are intended to capture certain key features from the existing

paper FIRMs.  These features include:

 

    > 100-year and 500-year (1% and 0.2% annual chance) floodplain areas,

      including Zone V areas, certain floodway areas (when present on the FIRM),

      and zone designations.

 

    > Coastal Barrier Resources Act (COBRA) areas.

 

    > Political areas, including community identification number.

 

    > FIRM panel areas, including panel number and suffix.

 

    > U.S. Geological Survey (USGS) 1:24,000 scale topographic quadrangle corner

      points and neatlines.

 

The most current FIRM panels are used in the Q3 Flood Data production.  In

addition, Letters of Map Amendment (LOMAs) and Letters of Map Revision (LOMRs),

if they are mappable at the publication scale of the paper FIRM, are incorporated

into the Q3 Flood Data.  However, the user should keep in mind that changes may

have occurred between the time of the digital Q3 Flood Data conversion and the

production date of the CD-ROM.  Therefore, because of the dynamic nature of these

revisions and updates, the user should confirm that the most up-to-date information

is being used to meet the needs of her/his desired application.  FEMA intends to

perform bi-annual reviews (and possible revisions) of the Q3 Flood Data CD-ROMs to

ensure the most current and useful data are available to the user community.

 

The paper FIRMs from which the Q3 Flood Data are extracted contain no horizontal

control (x/y, latitude/longitude coordinates).  However, the digital Q3 Flood Data

specifications require horizontal control consistent with the specifications required

for mapping at a scale of 1:24,000.  Horizontal control is typically accomplished by

fitting the flood data to a USGS 1:24,000 scale topographic quadrangle.  Edge-

matching errors, overlaps and underlaps in coverage, and similar problems are not

corrected during the Q3 Flood Data conversion process.

 

The Q3 Flood Data are distributed in USGS Digital Line Graph (DLG) format, compatible

with FEMA document FIA-21/October 1993 ("Standards for Digital Flood Insurance

Rate Maps").  The Q3 data are also provided in proprietary formats (ARC/INFO (R)

and MapInfo (R)) for use with numerous compatible desk-top mapping and Geographic

Information System (GIS) software packages.

 

LINKS TO ADDITIONAL DOCUMENTATION:

 

 

1.  USERGD.TXT.........."Q3 Users Guide" documentation provides users

                        with an overview of the Q3 Flood Data in an ASCII

                        text format.

 

4.  Q3SPEC.TXT.........."Q3 Specifications" documentation for the Q3 Flood

                        Data in ASCII text format.