AGSL GIS: DSD FEMA

Digital Spatial Data Clearing House

Digital Spatial Data

FEMA Q3 Flood Data (Illinois & Wisconsin)

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 CD. 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.

Spatial coverage: selected counties of Wisconsin and Illinois
Temporal coverage: Varies
Scale: 1:24,000
Format: DLG, E00 (ArcInfo Exchange file), MIF
Coordinate System: NAD1983
Access Constraints: UWM faculty and students, educational use only

Descriptions

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 System (CBRS) 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.

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