OVERVIEW

These data represent a subset of the data available on the paper Flood Insurance Rate Maps (FIRM) as provided by the Federal Emergency Management Agency (FEMA). The Q3 flood data were developed to support floodplain management and planning activities but do not replace the official paper FIRMs. These data are not suitable for engineering applications or site work nor can the data be used to determine absolute delineations of flood boundaries. Instead the data should be used to portray zones of uncertainty and possible risks associated with flooding. All counties except Franklin are available for Massachusetts. In ArcSDE the layer is named Q3FLOOD_POLY.

FEMA created the Q3 Flood data by scanning current FIRM paper maps and vectorizing the data. Though the scales of the map sheets vary and the original paper FIRMs contain no horizontal control, the data do have horizontal control consistent with 1:24,000 maps. This was accomplished by fitting the flood data to a USGS quadrangle. Edgematching, overlaps and underlaps in data and other problems were not corrected during the conversion process. The data were received from FEMA as ARC/INFO export files which were processed by MassGIS and incorporated into the data library. While FEMA intends to perform bi-annual review of data, the user is advised to confirm that the digital data does indeed represent the most current FIRM.

The attributes for the datalayer have been minimally modified by the addition of the item COUNTY. All other items are as supplied by FEMA. The FEMA-generated metafiles (included in this layer's download file - link at the top of this page) contain detailed descriptions of all fields.

The polygon attribute table has the following structure:

Item Name		Width		Type		Description
COUNTY		10		C		County name
FIPS		5		C		5-digit state and county FIPS CODE
COMMUNITY		4		C		County city or community responsible for floodplain mgmt
FIRM_PANEL		11		C		Code to identify portion of community covered/not covered by FIRM panel. The user can determine the date of the source FIRM by searching for the panel ID on FEMA’s Map Service Center website: Under "Product Search by..." click on "Map Panel ID".
QUAD		8		C		FEMA id to identify USGS 7.5 minute quad
ZONE		5		C		Flood hazard zone designation - See TABLE explaining codes.
FLOODWAY		5		C		Channel river or watercourse reserved for flood discharge
COBRA		9		C		ID whether in or out of coastal barrier resources system area
SFHA		3		C		In/out of flood zone designation
SYMBOL		4		B		FEMA polygon shade symbol for graphic output
PANEL_TYP		4		C		Type of FIRM panel represented

The datalayer is managed by MassGIS but no effort has been or will be made to correct data discrepancies. FEMA does not recommend the alteration of the data. As a final reminder, these data do not replace the paper FIRMs which remain the official documents.

FEMA and ESRI have created a web site that allows the user to create an online Hazard Map for your area of interest.

For complete metadata (documentation), refer to the documents included in this layer's download file, or see these Web pages:

• Q3 Users Guide: http://msc.fema.gov/webapp/wcs/stores/mapstore/docs/nuser_gd.pdf
• Digital Q3 Flood Data Specifications: http://msc.fema.gov/webapp/wcs/stores/mapstore/docs/q3spec.pdf

FEMA and the state's Department of Conservation and Recreation have partnered for FEMA Flood Map Modernization. For more on this project see the September, 2006 MGIC Seminar Series on the Digital FIRM (DFIRM) update program.

In June, 2007, a revised version was added to MassGIS' ArcSDE database: the layer was dissolved on all items to remove boundaries based on the original USGS quad index. At this time a new statewide shapefile was posted to the ftp site and download by USGS quad tile was discontinued.

Last Updated 1/24/2012
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