FEMA

National Flood
Hazard Layer (NFHL)
New Products and Services for FEMA’s
Flood Hazard Map Data
What is the NFHL?
The NFHL is a computer database that contains the flood hazard map
information from FEMA’s Flood Map Modernization program. These map
data are from Digital Flood Insurance Rate Map (DFIRM) databases and
Letters of Map Revision (LOMRs).
How Does the NFHL Benefit Me?
Benefits of the NFHL include:
? Convenience: The NFHL provides DFIRM and LOMR data as one
integrated dataset. You no longer need to obtain individual DFIRM
databases or Flood Insurance Rate Map (FIRM) panels and then locate and
integrate the subsequent changes caused by LOMRs. You still must review
changes identified by property descriptions, such as Letters of Map
Amendment (LOMAs) and Letters of Map Revision Based on Fill
(LOMR-Fs).
? Completeness: An NFHL dataset includes all the digital flood hazard data
that are effective and available as of the dataset release date.
? Flexibility: Like FEMA’s DFIRM database product, the NFHL Geographic
Information System (GIS) data and web map service can be integrated with
other map data, providing new options for using FEMA flood hazard
information.
Are NFHL data available for all of the U.S.?
No. As of June 2008, the NFHL included coverage for approximately 35
percent of the U.S. population. By 2010, FEMA anticipates having
coverage for 92 percent of the population and 65 percent of the land area.
If you need information for areas not covered by the NFHL, other FEMA
flood hazard map products and services provide coverage for larger areas
of the Nation. These products include FIRMs, FIRM Scans (digital images
of the FIRMs), FIRMettes (portions of FIRM Scans) created with the
FIRMette – Web or FIRMette – Desktop tools, and DFIRM databases.

Where Can I Obtain NFHL Flood Hazard Map
Products and Services?
The NFHL and other flood hazard map products and
services are available through the FEMA Map Service
Center (MSC) at http://msc.fema.gov.
What NFHL Products and Services are
Available?
The NFHL data are available in the following forms.
?MapViewer – Web: Use MapViewer – Web (see Figure
1) to view maps, look up attribute information, and
create custom maps and reports from NFHL data over
the web. MapViewer – Web also displays locations
affected by LOMAs and LOMR-Fs and provides access
to the determination documents for many of them. To
use MapViewer – Web you need a web browser (such as
Microsoft® Internet Explorer®1 or Mozilla® Firefox®1),
an Internet connection, and software that displays and
prints Portable Document Format (PDF) files.
Figure 1. MapViewer –
Web allows users to view
maps, look up attribute
information, and create
custom maps and reports.
? Utility files for viewing the NFHL data in Google
Earth™1: FEMA offers utility files (called “.kmz” files)
for viewing NFHL data in Google Earth (see Figure 2).
This capability is simple to use and allows the viewing
of basic map overlays. It does not provide access to all
NFHL data or reports. To use this capability you need
Google Earth installed on your computer, a high-speed
Internet connection, and the .kmz files.
Figure 2. Flood hazard map layers created from
NFHL data overlaid on imagery and 3-d buildings
using Google Earth.

?Web Map Service (WMS): Use WMS map layers to
create custom map images from NFHL data (see Figure
3). These images can be overlaid on other map data. You
also can look up attribute information from NFHL data.
To use the WMS you need web-based mapping or GIS
software that displays WMS images and a high speed
Internet connection. For
some software, adding
WMS images merely
requires the entry of a
URL. Other software
choices require more
work.
Figure 3. WMS map overlay created from NFHL data.
? NFHL GIS datasets: Use these data to create maps and
perform spatial analyses (see Figure 4). The data are
organized on a State-by-State basis, made available in
the ESRI™ Shapefile format, and delivered on computer
media from the MSC. They do not include the
orthophotos that
accompany some DFIRM
databases. To use these
data you need GIS software
that can read the Shapefile
format. A standalone
MapViewer – Desktop tool
(beta release), available
from the MSC, allows you
to view NFHL GIS data
and DFIRM databases
loaded on your computer.
Figure 4. NFHL GIS map and attribute data viewed with GIS software.
Which NFHL Product or Service is Right for
Me?
Selecting the right product depends on the task you need
to do and the capabilities available to you. If you only
need to view flood hazard data, the Google Earth and
MapViewer – Web options are the most straightforward.
If you need to combine flood hazard data with other
information, the WMS (for visual comparisons) and
NFHL GIS data (for more detailed analyses) are better
choices, although they require more effort to use. Table
1 provides a summary of some options.

How Often is the NFHL Database Updated?
FEMA incorporates available new DFIRM and LOMR
data on their effective date. The MapViewer – Web, map
overlays viewable in Google Earth, and WMS images
show these updates immediately. FEMA provides new
releases of the NFHL GIS data monthly. Between these
releases, the MSC makes available new FIRMs, FIRM
Scans, FIRMettes, DFIRM databases, and LOMRs.
Table 1. Options for using FEMA flood hazard map products and
services. NFHL products and services are highlighted in red.

May I Use FEMA’s Digital Flood Hazard Data
for Official Purposes?
Yes, assuming you comply with FEMA’s “Use of
Digital Flood Hazard Data” policy. The policy and
related information are available at
http://www.fema.gov/library/viewRecord.do?id=3235.
In particular, please ensure that other maps used with the
flood hazard data meet FEMA’s standards for map
accuracy2.
May I Still Use Other FEMA Flood Map
Products and Services?
Yes. FIRMs, FIRM Scans, FIRMettes, and DFIRM
databases are available for your use. The NFHL products
and services increase your options for using flood hazard
data. All of these items are available through the MSC.



Sources of Additional
Information
To view and buy flood maps and
data: See the MSC Web site at
http://msc.fema.gov.
For information and resources
associated with using or
requesting changes to FEMA Flood
Maps: See the Flood Hazard
Mapping Web site at
http://www.fema.gov/plan/
prevent/fhm/index.shtm.
For general information about
flood risk, flood insurance, and the
National Flood Insurance Program:
See the FloodSmart Web site at
http://www. FloodSmart.gov.

1Names of products are provided for descriptive purposes only and do not represent an endorsement by the United States Government.

2 A base map shows the location of roads and railroads, streams and lakes, boundaries, structures, and
other features. When used with flood hazard data for official purposes, base maps must have a horizontal
radial accuracy (Accuracyr) better than or equal to 38 feet (11.58 meters), as measured using the
National Standard for Spatial Data Accuracy. (This measure is equal to maps of scales larger than or
equal to 1:12,000 under the old National Map Accuracy Standard.)

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