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This is a brief description of layers and terms used on the map legend.

Base Flood Elevation (BFE) - The elevation of surface water resulting from a flood that has a 1-percent chance of equaling or exceeding that level in any given year. The BFE is shown on the Flood Insurance Rate Map (FIRM) for zone AE.  The 1-percent annual chance flood is also referred to as the “base flood” or “100-year flood”.

FEMA (Federal Emergency Management Agency) - The federal agency under which the National Flood Insurance Program is administered among other programs and actions for coordinating disaster response, mitigation, planning, and prevention.  In March 2003, FEMA became part of the newly created U.S. Department of Homeland Security.

Parcel or PIN - The PIN or Parcel Identification Number (PIN) is used by the Loudoun County Government to identify the property.  Another term for PIN that you may see is Map Cell Parcel Identification (MCPI).

SFHA -The land area having special flood hazards and shown on a Flood Insurance Rate Map (FIRM) as Zones A and AE, among other flood zones. Note: Flood insurance is only required by the National Flood Insurance Program (NFIP) for a building, dwelling, structure, or improvement that has a federally-backed loan and has any part of the structure situated in a Special Flood Hazard Area (SFHA). Flood insurance is not required by the NFIP if only the land is in the SFHA.  However, the mortgage company that makes the loan may choose to require flood insurance even though it is not required by the NFIP.  FEMA Page on SFHA
  • SFHA (ZONE A) - Areas subject to inundation by the 1-percent annual chance flood event generally determined using approximate methodologies. Because detailed hydraulic analyses have not been performed, no Base Flood Elevations (BFEs) or flood depths are shown. Mandatory NFIP flood insurance purchase requirements apply and floodplain management standards of your local community apply.  FEMA Page on ZONE A

  • SFHA (ZONE AE) - Areas subject to inundation by the 1-percent annual chance flood event determined by detailed methods. Base Flood Elevations (BFEs) are shown.  Mandatory NFIP flood insurance purchase requirements apply and floodplain management standards of your local community apply. FEMA Page on ZONE AE

  • SFHA (FLOODWAY) - A "Regulatory Floodway" means the channel of a river or other watercourse and the adjacent land areas that must be reserved in order to discharge the base flood without cumulatively increasing the water surface elevation more than a designated height. Communities must regulate development in these floodways to ensure that there are no increases in upstream flood elevations.  Local community floodplain management standards apply where a floodway is mapped.  FEMA Page on FLOODWAY

SFHA Change* – Difference between the Pending FIRM and current, Effective FIRM.
  • ADDED – Yellow-highlighted area added as SFHA on the Pending FIRM compared to the Effective FIRM
  • REMOVED – Green-highlighted area removed as SFHA on the Pending FIRM compared to the Effective FIRM
  • SFHA – Blue-highlighted area is SFHA in the same location on both the Effective FIRM and the Pending FIRM.
*Note that the SFHA Zone designation may have changed from A to AE between the Effective FIRM and the Pending FIRM. Go to the “FEMA Detail” tab for a view of the full extent of the Pending SFHA and identification of Zones A and AE.

Other Areas of Flood Hazard
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Includes areas of moderate and minimal flood hazard. These areas are not regulated as part of the NFIP.  Areas of moderate flood hazard (called “Shaded Zone X”) may be regulated by local communities.
Minor Floodplain - Area draining between 100 and 640 acres and subject to inundation by the 1-percent annual chance (100-year) flood event.

500-Year Floodplain - Area between the limits of the base flood (1-percent chance annual flood; Zones A and AE) and 0.2 (500 year) flood.  This area is not regulated by Loudoun County or FEMA.

Note: The Pending FIRM will become effective February 17, 2017. 

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