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Web Map Service (WMS) for the FEMA National Flood Hazard Layer (NFHL) and Related Items

A Web Map Service creates georeferenced map images from a computer database and provides the images over the web. Most Geographic Information System (GIS) software and web-based mapping applications can display the images provided by Web Map Services.

FEMA provides access to the National Flood Hazard Layer through a Web Map Service. The National Flood Hazard Layer is a computer database that contains FEMA's flood hazard map data. The data depict flood hazard information and supporting data used to develop the information. The primary hazard classifications are the 1 percent-annual-chance flood event, the 0.2 percent-annual-chance flood event, and areas of minimal flood hazard.

Flood hazard and supporting data are developed using specifications for horizontal control consistent with 1:12,000-scale mapping. If you plan to display maps from the National Flood Hazard Layer with other map data for official purposes, ensure that the other information meets FEMA's standards for map accuracy.

The NFHL data are from FEMA's Digital Flood Insurance Rate Map (DFIRM) databases. New data are added continually. The NFHL also contains changes to DFIRM data made by Letters of Map Revision (LOMRs).

The service provides map images geo-referenced to the earth's surface using the North American Datum of 1983, Geodetic Reference System 80 coordinate system.

The service also provides information that complements the National Flood Hazard Layer. In areas for which data are not available from the National Flood Hazard Layer, an older set of flood hazard data, named the "Q3" data, may be available. The service also provides information about the availability of flood data and maps, the national map panel scheme, river subbasins, and point locations for Letters of Map Amendment (LOMA) and Letters of Map Revision Based on Fill (LOMR-Fs). These complementary data are positioned less accurately than are the National Flood Hazard Layer data.

The service organizes the data in layers. The layers display information at map scales appropriate for the data. Status information and river subbasins are displayed at map scales smaller than 1:300,000, regional overviews at map scales between 1:300,000 and 1:32,000, and detailed flood hazard maps at map scales of 1:32,000 and larger. The "Scalehint" item in the Capabilities file for the Web Map Service encodes the scale range for maps for a layer.

The service complies with WMS Interface Specification 1.1.1 developed by the Open Geospatial Consortium, Inc. The service responds to the GetCapabilities, GetMap, and GetFeatureInfo operations defined by the specification. More information about the specification is available at www.opengeospatial.org/standards/wms.


NFHL service

The "NFHL" service provides access to most features in the NFHL and has map symbols that highlight flood hazards.

NFHL WMS Instructions

The URL for the WMS Capabilities file is:

http://hazards.fema.gov/wmsconnector/wmsconnector/Servlet/NFHL?REQUEST=GetCapabilities&SERVICE=WMS

The service responds to GetMap requests at the URL:

http://hazards.fema.gov/wmsconnector/wmsconnector/Servlet/NFHL?VERSION=1.1.1&REQUEST=GetMap&

followed by your WMS GetMap parameters that describe a particular map.

The service responds to GetFeatureInfo requests through the URL:

http://hazards.fema.gov/wmsconnector/wmsconnector/Servlet/NFHL?VERSION=1.1.1&EST=GetFeatureInfo&

followed by your WMS GetFeatureInfo parameters that describe a particular map, and the layer(s) and the location on the map for which the information is requested.

GIS software and web-based mapping applications that display images from a Web Map Service use these URLs to access the service. See the documentation for your software to learn the preferred method of adding a Web Map Service.

See the web site "Flood Data Symbology for Web Map Services" for the titles of layers, the names of the features they include, and the map symbols for the features.

FEMA released a new version of the NFHL WMS in early August 2008. The WMS now:

  • Displays only the boundaries of "effective" Letters of Map Revision.
  • Displays the case numbers of Letters of Map Amendment and Letters of Map Revision Based on Fill (at 1:32,000 scale and larger).
  • Displays map layers in a more useful drawing order.
  • Has new map symbols that provide better contrast when overlaid on aerial images.
  • Provides layers that, when used together, create an image that shows flood hazard areas and areas for which there are no data in the NFHL.
  • Provides images that match the map provided by the "e–z Print" function in the MapViewer – Web tool.

NOTICE: FEMA withdrew the old WMS named "flood" from service on November 30, 2008. Please use the NFHL WMS in its place.