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How Are Flood Zones Determined?

Flood zones classifiy the probability an area has of flood risk. Many times, it’s not until someone is purchasing a house or are faced with an imminent natural disaster such as a hurricane, that they learn more about the flood zone of their property. The Federal Emergency Management Agency (FEMA) operates the official flood hazard Mapping Service Center (MSC) in support of the national flood insurance program and offers flood zone maps online.

Flood Zone Classification

There are 15 categories to classify floodplains and these correspond to the full range of flooding potential.

  • V Zones – According to FEMA and the National Flood Insurance Program, any building located in an A or V zone is considered to be in a Special Flood Hazard Area. This means that it is lower than the Base Flood Elevation. V zones are the most hazardous of the Special Flood Hazard Areas and generally include the first row of beachfront properties. The hazards in these areas are increased because of wave velocity. Flood insurance is mandatory in V zone areas.
  • A Zones – are the next most volatile of the Special Flood Hazard Areas because they are subject to rising waters and are usually near a lake, river, stream or another body of water. Flood insurance is mandatory in all A zones because of the high potential of flooding. A-zone maps also include AE, AH, AO, AR and A99 designations, all having the same rates. The different A zones are named depending on the way in which they might be flooded.
  • Zone C to Zone X – are with minimal risk of flooding. These areas are located outside the 500-year floodplain. There is a 1 to 2 percent annual probability of flooding.
  • D Zones – refer to areas that have not been studied but where flooding is possible.

How Are Flood Zones Determined?

Flood zones are primarily determined by the history of flooding in the area. Each zone is rated according to the probability of annual flooding.

According to FEMA, Special Flood Hazard Areas “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.”

How To Access Your Flood Insurance Rate Map

Flood Insurance Rate Map (FIRM) is the map that displays the special flood hazard areas and the risk premium zones applicable to your community. There are several options to view your property or community’s flood risk:

  • Visit your Community Map Repository, which is usually maintained by the community floodplain administrator or officials at the planning and zoning office and ask for a copy of your property’s FIRM panel.
  • View and download the FIRM from the FEMA Flood Map Service Center
  • View and download the National Flood Hazard Layer (NFHL) data using the FEMA GeoPortal. To learn more about the NFHL and how to use it, visit the National Flood Hazard Layer (NFHL).

If you have any doubts about your flood zone classification, contact us today for a free flood zone audit.

1 thought on “How Are Flood Zones Determined?

  1. Does Fema Use the Lunar Cycle to determine new Base Flood Elevations in Flood Zones?

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