Flood Data Viewers and Geospatial Data

The National Flood Hazard Layer (NFHL) is a geospatial database that contains current effective flood hazard data. FEMA provides the flood hazard data to support the National Flood Insurance Program. You can use the information to better understand your level of flood risk and type of flooding. The NFHL can also be used in place of the FIRM for NFIP purposes with appropriate care.

The NFHL is made from effective flood maps and Letters of Map Change (LOMC) delivered to communities. NFHL digital data covers over 90% of the U.S. population.  New and revised data is being added continuously. If you need information for areas not covered by the NFHL data, there may be other FEMA products which provide coverage for those areas.

Accessing the National Flood Hazard Layer

In the NFHL Viewer, you can use the address search or map navigation to locate an area of interest and the NFHL Print Tool to download and print a full Flood Insurance Rate Map (FIRM) or FIRMette (a smaller, printable version of a FIRM) where NFHL data exists. Technical GIS users can also utilize a series of dedicated GIS web services that allow the NFHL database to be incorporated into websites and GIS applications. For more information on available services, go to the NFHL GIS Services User Guide.

You can also use the address search on the FEMA Flood Map Service Center (MSC) to view the NFHL data or download a FIRMette. Using the “Search All Products” on the MSC, you can download the NFHL data for a County or State in a GIS file format. This data can be used in most GIS applications to perform spatial analyses and for integration into custom maps and reports. To do so, you will need GIS or mapping software that can read data in shapefile format.

FEMA also offers a download of a KMZ (keyhole markup file zipped) file, which overlays the data in Google Earth™. For more information on using the data in Google Earth™, please see Using the National Flood Hazard Layer Web Map Service (WMS) in Google Earth™.

Preliminary flood hazard data provides the public an early look at their home or community’s projected risk to flood hazards. Before they become effective, the preliminary products go through a formal review period that provides the opportunity to appeal the preliminary determinations with better data. Preliminary FIRM products help community officials and property owners see how upcoming flood mapping changes will affect them. Community officials and property owners can also review the data for accuracy. Preliminary data may include new or revised Flood Insurance Rate Maps (FIRM), Flood Insurance Study (FIS) Reports and FIRM Databases. If preliminary data is available for your community, you can view it and compare it with existing data on the Flood Map Changes Viewer.

Pending Flood Insurance Rate Map (FIRM) Databases are scheduled to be adopted by the local government and become effective within six months. This is the final step in the process before new flood hazard data becomes effective. Pending FIRM Databases have been designated final by the Letter of Final Determination issued to community officials. However, they do not officially define the minimum requirements for National Flood Insurance Program (NFIP) purposes until they become effective at the end of the six-month adoption and compliance period.   

They are published in the Pending NFHL as soon as possible to give community officials, lenders, and the public time to prepare for new official data. Pending data may include new or revised Flood Insurance Rate Maps (FIRM), Flood Insurance Study (FIS) Reports and FIRM Databases. If pending data is available for your community, you can view it and compare it with existing data on the Flood Map Changes Viewer.

The Flood Hazard and Risk Data Viewer shares a variety of flood hazard and risk data from FEMA. This viewer provides a single location to view a large inventory of data that represents both current and future flood conditions to help users understand their flood hazard and other risk-related information. Some flood hazard and flood risk data produced by FEMA define minimum requirements for the National Flood Insurance Program (NFIP). This viewer includes these required NFIP data and includes other data showing current and potential future flood hazard and risk. This provides users access to more complete flood hazard data. FEMA also uses this viewer to provide communities an opportunity to comment on early drafts of flood hazard data.

The MSC or NFHL Viewer is the best place to start to understand the official NFIP flood hazard determinations for your area of interest. Where an effective flood map exists and provides data, that data must be used to establish the minimum NFIP requirements.

If an update to a community’ flood maps is ongoing, The Flood Map Changes Viewer allows the user to compare preliminary or pending changes to any current flood data for the community.

If effective data is not available in your community, or you are interested in more information about flood risk in your area, the Flood Hazard and Risk Data Viewer may have information beyond information in the sources above that focus on the regulatory NFIP requirements. This includes information about sea level rise in coastal areas and base level engineering products from FEMA.  The BLE data may progress and eventually be included in the Effective NFHL, or they may not.  See Base Level Engineering Resources for more information.

Making Official Determinations

The NFHL Database and NFHL GIS Services can be used in maps or application that combine the NFHL flood hazard data with basemaps and other reference data from other sources. However, to use the effective NFHL data for official purposes, you are responsible for making sure base map data meet FEMA’s accuracy standards and the locations depicted are interpreted properly. The NFHL Viewer and FIRMettes from the MSC provide a default base map that meets the minimum standards.

For the specifics of FEMA’s policy on the use of digital flood hazard data for NFIP purposes, see standards 147, 148, 149, 605, and 606 in the FEMA Policy Standards for Flood Risk Analysis and Mapping.