National Flood Hazard - Letter of Map Amendment (LOMA)

The LOMA point layer indicates coordinates for Letters of Map Amendment, which can affect flood zone determination without a map change. Please be aware that LOMA point layer is provided ‘as-is’ and that there are several issues that must be considered before using this information. The first is its positional accuracy. Where the point is shown on the map may, or may not, be totally accurate as there are a variety of methods that can be used to translate a mailing address into a geographic coordinate (geocoding). The second is the completeness of the dataset. This point layer only includes LOMAs that have a coordinate associated with them. There are a number of LOMAs that have been processed by FEMA which do not have any type of a coordinate associated with them and those LOMAs are not included within this data.<div><p>Technical Reference - <a href='http://www.fema.gov/media-library-data/1449862521789-e97ed4c7b7405faa7c3691603137ec40/FIRM_Database_Technical_Reference_Nov_2015.pdf'>http://www.fema.gov/media-library-data/1449862521789-e97ed4c7b7405faa7c3691603137ec40/FIRM_Database_Technical_Reference_Nov_2015.pdf</a></p><p>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. </p><p>The minimum horizontal positional accuracy for base map hydrographic and transportation features used with the NFHL is the NSSDA radial accuracy of 38 feet. USGS imagery and map services that meet this standard can be found by visiting the Knowledge Sharing Site (KSS) for <a href='http://pm.riskmapcds.com/kss/Lists/KSS_Standards2/DispForm.aspx?ID=2566'>Base Map Standards (420)</a>. Other base map standards can be found at <a href='https://riskmapportal.msc.fema.gov/kss/MapChanges/default.aspx'>https://riskmapportal.msc.fema.gov/kss/MapChanges/default.aspx</a>. You will need a username and password to access this information.</p><p>The NFHL data are from FEMA’s Flood Insurance Rate Map (FIRM) databases. New data are added continually. The NFHL also contains map changes to FIRM data made by Letters of Map Revision (LOMRs). </p><p>The NFHL is stored in North American Datum of 1983, Geodetic Reference System 80 coordinate system, though many of the NFHL GIS web services support the Web Mercator Sphere projection commonly used in web mapping applications. </p></div>