Frequently Asked Questions

Q3 Flood Data

  1. What is the digital Q3 Flood Data product?
  2. Why was the digital Q3 Flood Data product developed?
  3. How are the digital Q3 Flood Data created?
  4. What are the uses of the digital Q3 Flood Data?
  5. What are the limitations of the digital Q3 Flood Data?
  6. What features are in the digital Q3 Flood Data files?
  7. What features are not in the digital Q3 Flood Data files?
  8. How many data layers are included in the digital Q3 Flood Data?
  9. Will the digital Q3 Flood Data CD-ROM let me display flood maps?
  10. What is the scale of digital Q3 Flood Data?
  11. Do the digital Q3 Flood Data include a base map?
  12. May I change the floodplain boundary delineations in the digital Q3 Flood Data?
  13. May I add cross-section lines to the map?
  14. Can I locate a street address (e.g. residential or commercial buildings) with the digital Q3 Flood Data?
  15. Can I make flood risk determinations with these data?
  16. How can I view the digital Q3 Flood Data?
  17. In what data formats are the digital Q3 Flood Data available?
  18. Can you recommend desktop mapping or Geographic Information Systems (GIS) software that I can purchase?
  19. Has a digital flood map been produced for my county?
  20. Will digital flood maps for additional counties be produced?
  21. How are the Q3 Flood Data distributed?
  22. How often will the digital Q3 Flood Data be updated?
  23. How do I find out about the digital Q3 Flood Data production and updating schedule?
  24. Do the digital Q3 Flood Data Files represent the current effective Flood Insurance Rate Map panels?
  25. Can the digital Q3 Flood Data be used as the legal or official Flood Insurance Rate Map document?
  26. What do I do if I find inaccuracies or inconsistencies in the data?
  1. What is the digital Q3 Flood Data product?

    The Q3 Flood Data product is a digital representation of certain features of FEMA's Flood Insurance Rate Map (FIRM) product, intended for use with desktop mapping and Geographic Information Systems technology. Digital Q3 Flood Data has been developed by scanning the existing FIRM hardcopy, vectorizing a thematic overlay of flood risks. The vector Q3 Flood Data files contain only certain features from the existing FIRM hardcopy.

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  2. Why was the digital Q3 Flood Data product developed?

    The digital Q3 Flood Data product was designed to:

    1. Serve the needs of FEMA's Response and Recovery activities after flood disaster
    2. Promote flood insurance policy marketing initiatives
    3. Assist in floodplain management activities at the local level

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  3. How are the digital Q3 Flood Data created?

    The digital Q3 Flood Data are created by scanning the effective Flood Insurance Rate Map (FIRM) paper maps and digitizing selected features and lines. Usually, FIRMs for the cities and towns within a county are also digitized and combined with the county to produce a countywide map.

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  4. What are the uses of the digital Q3 Flood Data?

    The digital Q3 Flood Data are designed to serve FEMA's needs for disaster response activities, National Flood Insurance Program activities, risk assessment, and floodplain management. The data are expected to be used for a variety of planning applications including broad-based review for floodplain management, land-use planning, commercial site analysis, insurance target marketing, natural resource/environmental analyses, and real estate development and targeting.

    Because digital Q3 Flood Data are controlled to the USGS 1:24,000 scale maps, they may not be detailed enough for some uses. The hardcopy Flood Insurance Rate Map or Digital Flood Insurance Rate Map should be used to make official determinations, especially if a property is close to the boundary of the mapped Special Flood Hazard Area.

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  5. What are the limitations of the digital Q3 Flood Data?

    Because of the scale of the digital Q3 Flood Data, it cannot be used to determine absolute delineations of flood risk boundaries. It is especially important to understand the "buffer" that FEMA recommends users apply to the floodplain boundary. The buffer is 250 feet outside of the floodplain boundary line. Users should refer to the official hardcopy map if a site of interest falls in the buffer. See the "Q3 Flood Data Users Guide" and "Q3 Flood Data Specifications" for more information.

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  6. What features are in the digital Q3 Flood Data files?

    The digital Q3 Flood Data contain the following:

    1. 1-percent (100-year) and 0.2-percent (500-year) annual chance floodplain boundaries (including velocity zones),
    2. flood insurance zone designations,
    3. floodway boundaries (where available),
    4. political boundaries (State, county, and community),
    5. community and map panel identification numbers,
    6. Flood Insurance Rate Map (FIRM) panel neatlines,
    7. United States Geological Survey (USGS) 7.5-minute (1:24,000 scale) series topographic map neatlines, and
    8. Coastal Barrier Resources System areas.

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  7. What features are not in the digital Q3 Flood Data files?

    The digital Q3 Flood Data do not contain the following data features that are shown on the official paper Flood Insurance Rate Map:

    1. hydrographic features (streams and river, lake and coastal shorelines),
    2. base flood elevations,
    3. cross section lines,
    4. roads, road names, or address ranges, and
    5. locations, elevations and descriptions of benchmarks and elevation reference marks.

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  8. How many data layers are included in the digital Q3 Flood Data?

    One. Digitial Q3 Flood Data are digitized scans of harcopy Flood Insurance Rate Maps. All features contained in the digital Q3 Flood Data files are stored on one countywide data layer.

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  9. Will the digital Q3 Flood Data CD-ROM let me display flood maps?

    The CD-ROM with the digital Q3 Flood Data contains certain key data and information found on Flood Insurance Rate Maps. The Flood Data, not the maps themselves. You will need mapping software and a digital base map as a foundation on which to overlay the digital Q3 Flood Data.

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  10. What is the scale of digital Q3 Flood Data?

    Q3 Flood Data are captured from the actual Flood Insurance Rate Maps at publication scale, but the digital data have horizontal control specifications consistent only with 1:24,000 scale mapping. When using desk-top mapping or Geographic Information Systems (GIS) software, the user can view or print the digital Q3 Flood Data at large scales (i.e., 1:500 or 1:1,000); however, the data will have the horizontal control of only the 1:24,000 scale map.

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  11. Do the digital Q3 Flood Data include a base map?

    No. However, they are horizontally controlled to United States Geologic Survey (USGS) 1:24,000 scale quadrangles. This allows users to overlay the digital Q3 Flood Data with their own geographic information or base map.

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  12. May I change the floodplain boundary delineations in the digital Q3 Flood Data?

    The locations of the Special Flood Hazard Areas shown on the hard copy Flood Insurance Rate Maps are derived from hydrologic and hydraulic engineering models or other approved methods to delineate flood prone areas. Although FEMA recognizes that processing may introduce differences with the hardcopy, FEMA does not recommend the alteration of the digital Q3 Flood Data product. Users must use considerable care and judgment in applying this product. Refer to the "Q3 Flood Data Users Guide" and "Q3 Flood Data Specifications" for further information and use policy.

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  13. May I add cross-section lines to the map?

    Users must apply considerable care and judgment when altering the digital Q3 Flood Data product and modifications are not recommended. The digital Q3 Flood Data product does not include cross section lines or base flood elevations, nor is it registered to a base map. Refer to the "Q3 Flood Data Users Guide" and "Q3 Flood Data Specifications" for further information.

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  14. Can I locate a street address (e.g. residential or commercial buildings) with the digital Q3 Flood Data?

    No. When you locate an address using computer mapping, you see an approximation of where the address is along the street or road. Commerial mapping software does not contain enough detail to locate the actual building. Many communities are converting tax maps or topographic maps to digital formats, which may give better information to determine if a building is in the floodplain.

    You can use the ESRI address software to estimate flood hazards and to develop estimates of how many homes and businesses are in the mapped floodplain.

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  15. Can I make flood risk determinations with these data?

    No. The digital Q3 Flood Data product was not designed to make precise in/out flood risk determinations. The data are designed to provide guidance and a general proximity of the location of Special Flood Hazard Areas. The digital Q3 Flood Data product is not suitable for engineering applications and cannot be used to determine absolute delineations of flood boundaries.

    Users must apply considerable care and judgment in applying this product. Users should refer to the "Q3 Flood Data Users Guide" and "Q3 Flood Data Specifications" for more information.

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  16. How can I view the digital Q3 Flood Data?

    Use your desktop mapping or Geographic Information System software to use this data. Q3 flood data is available in these three formats:

    1. Digital Line Graph (DLG)
    2. ARC/INFO ®
    3. MapInfo ®

    Additional mapping information can be found on the ESRI online hazard map website.

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  17. In what data formats are the digital Q3 Flood Data available?
    FEMA produces the Q3 Flood Data in three data formats that are usable with desktop mapping and Geographic Information System software packages. These formats are:
    1. Digital Line Graph (DLG)
    2. ARC/INFO ®
    3. MapInfo ®

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  18. Can you recommend desktop mapping or Geographic Information Systems (GIS) software that I can purchase?

    FEMA does not endorse or promote specific proprietary software packages. The digital Q3 Flood Data are produced in formats that are useable with most desktop mapping and Geographic Information System software programs. For more information see the "Q3 Flood Data Users Guide".

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  19. Has a digital flood map been produced for my county?

    FEMA has produced Q3 Flood Data for over 1,250 counties. To find out if your county has been prepared, see the Map Service Center Q3 Flood Data for a state-by-state listing.

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  20. Will digital flood maps for additional counties be produced?

    There are no immediate plans to prepare more Q3 Flood Data counties. FEMA has begun an agressive effort to modernize the maps. Sometimes, Q3 Flood Data files are produced to support a Presidentially declared disaster.

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  21. How are the Q3 Flood Data distributed?

    The data are distributed on CD-ROM and from ESRI's Web site. The data are arranged by states on CD-ROMs, with one or more states per CD-ROM. Coverage for some states may require two CD-ROMs.

    FEMA and ESRI signed a Partnership agreement making flood hazard maps available for all areas where FEMA has prepared Q3 flood data.

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  22. How often will the digital Q3 Flood Data be updated?

    The digital Q3 Flood Data are currently scheduled for review to determine the need for revisions and/or updates. Letters of Map Change and Physical Map Revisions will be assessed to determine the need for data updates. However, no specific update schedule has been determined to date.

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  23. How do I find out about the digital Q3 Flood Data production and updating schedule?

    Any questions, comments, or contributions to the production, utility, and distribution of the digital Q3 Flood Data product may be directed to the following address:

    Federal Emergency Management Agency
    Federal Insurance and Mitigation Administration
    Q3 Flood Data Program
    500 C Street, SW
    Washington, D.C. 20472

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  24. Do the digital Q3 Flood Data Files represent the current effective Flood Insurance Rate Map panels?

    Maybe. When the Q3 Flood Data are produced, FEMA uses the current data. However, Letters of Map Change or Physical Map Revisions may have appeared since the Q3 was prepared. The user is responsible for determining if the digital Q3 Flood Data have the same date as the effective Flood Insurance Rate Map panels.

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  25. Can the digital Q3 Flood Data be used as the legal or official Flood Insurance Rate Map document?

    No. The paper Flood Insurance Rate Map is the official document.

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  26. What do I do if I find inaccuracies or inconsistencies in the data?

    The digital Q3 Flood Data are scheduled for review to determine the need for revisions and/or updates. Although an update schedule has not been determined, FEMA would like to know when inaccuracies are found. Please report inaccuracies or inconsistencies to the following address:

    Federal Emergency Management Agency
    Federal Insurance and Mitigation Administration
    Q3 Flood Data Program
    500 C Street, SW
    Washington, D.C. 20472

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Last Modified: Thursday, 11-Oct-2007 11:07:54 EDT

Fast Facts

Additional FAQ Topics

Digital Flood Data and Mapping
General Information
Flood Insurance
Flood Map Policy and Program
Flood Map Process
Flood Revision
Flood Study Data
Frequently Used Terms
Q3 Flood Data

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