The National Flood Hazard Layer (NFHL) dataset represents the current effective flood data for the country, where ma
ps have been modernized. It is a compilation of effective Flood Insurance Rate Map (FIRM) databases and Letters of Map Change (LOMCs). The NFHL is updated as studies go effective. For more information, visit FEMA's Map Service Center (MSC).
Online Mapping Platforms
FEMA National Flood Hazard Layer Interactive Mapping
FEMA Flood Insurance Rate Map information can also be found on the Nassau County Property Appraiser's Interactive Mapping site.
Nassau County Property Appraiser Interactive Mapping
Letter of Map Amendment (LOMA) Points
LOMA point locations are approximate. The location of the LOMA is referenced in the legal description of the letter itself. Click the LOMA point for a link to the letter (use the arrows at the top of the popup window to bring up the LOMA info, if needed).
This LOMA database may include LOMAs that are no longer effective. To be certain a particular LOMA is currently valid, please check relevant documentation at https://msc.fema.gov/ . Relevant documents can be found for a particular community by choosing to "Search All Products", and finding the community by State and County. Documents include LOMAs found in the "Effective Products" and "LOMC" folders, as well as Revalidations (those LOMAs which are still considered to be effective after a map is revised).
Flood hazard areas identified on the Flood Insurance Rate Map as Special Flood Hazard Areas (SFHA). SFHAs are defined as the area that will be inundated by the flood event having a 1-percent chance of being equaled or exceeded in any given year. The 1-percent annual chance flood is also referred to as the base flood or 100-year flood. SFHAs are labeled as Zone A, AO, AH and VE. Moderate flood hazard areas, labeled Zone X500 (shaded) are also shown on the FIRM, and are the areas between the limits of the base flood and the 0.2-percent-annual-chance (or 500-year) flood. The areas of minimal flood hazard, which are the areas outside the SFHA and higher than the elevation of the 0.2-percent-annual-chance flood, are labeled Zone C or Zone X (unshaded).
Flood Zone Definitions
Zone A: Areas subject to inundation by the 1% annual chance flood event. Because detailed hydraulic analyses have not been performed, no Base Flood Elevations (BFEs) or flood depths are shown.
Zone AE: Areas subject to inundation by the 1% annual chance flood event determined by detailed methods. BFEs are shown within these zones.
Zone AH: Areas subject to inundation by 1% annual chance shallow flooding (usually areas of ponding) where average depths are 1–3 feet. BFEs derived from detailed hydraulic analyses are shown in this zone.
Zone AO: Areas subject to inundation by 1% annual chance shallow flooding (usually sheet flow on sloping terrain) where average depths are 1–3 feet. Average flood depths derived from detailed hydraulic analyses are shown within this zone.
Zone VE: Areas subject to inundation by the 1% annual chance flood event with additional hazards due to storm induced velocity wave action. Base Flood Elevations (BFE) are derived from from detailed hydraulic analysis. Mandatory purchase requirements and floodplain management standards apply.