The National Flood Hazard Layer compiles the current status of the FEMA National Flood Insurance Program’s Flood Insurance Rate Maps. This geospatial data is publicly available via GIS connection. It’s jam-packed with information revealing current and effective flood hazards around the country, and this GIS data is available to download as well.
What is a Flood Zone?
Flood hazard areas identified on the Flood Insurance Rate Map are identified as a Special Flood Hazard Area (SFHA). Special Flood Hazard Areas have special flood, mudflow, or flood-related erosion hazards and shown on a Flood Hazard Boundary Map (FHBM) or a Flood Insurance Rate Map (FIRM) Zone A, AO, A1-A30, AE, A99, AH, AR, AR/A, AR/AE, AR/AH, AR/AO, AR/A1-A30, V1-V30, VE or V.
Important: The SFHA is the area where the National Flood Insurance Program’s (NFIP’s) floodplain management regulations must be enforced and the area where the mandatory purchase of flood insurance applies. For the purpose of determining Community Rating System (CRS) premium discounts, all AR and A99 zones are treated as non-SFHAs.
The “100-Year” Floodplain
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 | The Special Flood Hazard Area (except coastal V Zones) shown on a community’s Flood Insurance Rate Map (FIRM). SFHA where no base flood elevation is provided. 100-year Floodplain, areas with a 1% annual chance of flooding. Because detailed analyses are not performed for such areas; no depths or base flood elevations are shown within these zones. |
| Zone AO | SFHA with sheet flow, ponding, or shallow flooding. Base flood depths (feet above grade) are provided. 100-year Floodplain, river or stream flood hazard areas, and areas with a 1% or greater chance of shallow flooding each year, usually in the form of sheet flow, with an average depth ranging from 1 to 3 feet. Average flood depths derived from detailed analyses are shown within these zones. |
| Zone AH | Shallow flooding SFHA. Base flood elevations in relation to a national datum are provided. 100-year Floodplain, areas with a 1% annual chance of shallow flooding, usually in the form of a pond, with an average depth ranging from 1 to 3 feet. flood elevations derived from detailed analyses are shown at selected intervals within these zones. |
| Zones A1-A30 | 100-year Floodplain. The base floodplain where base flood elevations are provided. AE Zones are now used on new format FIRMs instead of A1-A30 Zones. Numbered A Zones (e.g., A7 or A14), SFHA where an older FIRM shows a base flood elevation in relation to a national datum (See Below) |
| Zone AE | SFHA where base flood elevations are provided. AE-Zone delineations are used on newer FIRMs instead of A# Zones (See Above). |
| Zone A99 | A mapped floodplain that will be protected by a federal flood protection system where construction has reached specified statutory milestones. This zone is considered part of the Special Flood Hazard Area or “regulatory floodplain,” but properties in this zone do not receive the “in SFHA” CRS premium discount (see Table 110-1). |
| Zone AR | A temporary designation for an area where a flood control system that no longer provides protection from the base flood is expected to be improved so it will provide protection to the base flood again in the future. This zone is considered part of the Special Flood Hazard Area or “regulatory floodplain,” but properties in this zone do not receive the “in SFHA” CRS premium discount (see Table 110-1). There are four types of AR Zones: AR, AR/AE, AR/AO, AR/A#, and AR/A, and they correspond to the A-Zone designations. |
| Zone AR/AE | AR – temporary designation for an area where a flood control system that no longer provides protection from the base flood is expected to be improved so it will provide protection to the base flood again in the future. This zone is considered part of the Special Flood Hazard Area or “regulatory floodplain,” but properties in this zone do not receive the “in SFHA” CRS premium discount (see Table 110-1). AE- SFHA where base flood elevations are provided. AE-Zone delineations are used on newer FIRMs instead of AE# Zones (See Above). |
| Zone AR/AO | AR – temporary designation for an area where a flood control system that no longer provides protection from the base flood is expected to be improved so it will provide protection to the base flood again in the future. This zone is considered part of the Special Flood Hazard Area or “regulatory floodplain,” but properties in this zone do not receive the “in SFHA” CRS premium discount (see Table 110-1). AO – SFHA with sheet flow, ponding, or shallow flooding. Base flood depths (feet above grade) are provided. 100-year Floodplain, river or stream flood hazard areas, and areas with a 1% or greater chance of shallow flooding each year, usually in the form of sheet flow, with on average depth ranging from 1 to 3 feet. Average flood depths derived from detailed analyses are shown within these zones. |
| Zone AR/A1-A30 | AR – temporary designation for an area where a flood control system that no longer provides protection from the base flood is expected to be improved so it will provide protection to the base flood again in the future. This zone is considered part of the Special Flood Hazard Area or “regulatory floodplain,” but properties in this zone do not receive the “in SFHA” CRS premium discount (see Table 110-1). A# – 100-year Floodplain. The base floodplain where base flood elevations are provided. AE Zones are now used on new format FIRMs instead of A1-A30 Zones. Numbered A Zones (e.g., A7 or A14), SFHA where an older FIRM shows a base flood elevation in relation to a national datum (See Above) |
| Zone AR/A | AR – temporary designation for an area where a flood control system that no longer provides protection from the base flood is expected to be improved so it will provide protection to the base flood again in the future. This zone is considered part of the Special Flood Hazard Area or “regulatory floodplain,” but properties in this zone do not receive the “in SFHA” CRS premium discount (see Table 110-1). A – The Special Flood Hazard Area (except coastal V Zones) shown on a community’s Flood Insurance Rate Map (FIRM). SFHA where no base flood elevation is provided. 100-year Floodplain, areas with a 1% annual chance of flooding. Because detailed analyses are not performed for such areas; no depths or base flood elevations are shown within these zones. |
| Zone V | The Special Flood Hazard Area subject to coastal high hazard flooding. There are three types of V Zones: V, V#, and VE, and they correspond to the A-Zone designations. |
| Zone VE | The Special Flood Hazard Area subject to coastal high hazard flooding. SFHA where base flood elevations are provided. VE-Zone delineations are used on newer FIRMs instead of V# Zones (See below). |
| Zones V1-V30 | The Special Flood Hazard Area subject to coastal high hazard flooding. 100-year Floodplain. The base floodplain where base flood elevations are provided. VE Zones are now used on new format FIRMs instead of V1-V30 Zones. Numbered V Zones (e.g., V7 or V14), SFHA where an older FIRM shows a base flood elevation in relation to a national datum (See above) |
Moderate Flood Hazard – the “500-Year” Floodplain
Moderate flood hazard areas, labeled Zone B or Zone X (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.
| Zone B | Area of moderate flood hazard usually depicted on older Flood Insurance Rate Maps as between the limits of the base and 500-year floods of the primary source of flooding. B Zones may have local, shallow flooding problems. B Zones are also used to designate areas protected by levees and base floodplains of little hazard, such as those with average depths of less than 1 foot. |
| Zone X (Shaded) | Newer Flood Insurance Rate Maps show Zones B and C (see above) as Zone X. The shaded Zone X corresponds to Zone B |
Minimal flood hazard
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 (500-year flood), are labeled Zone C or Zone X (unshaded).
| Zone C | Area of minimal flood hazard usually depicted on older Flood Insurance Rate Maps as above the 500-year flood level of the primary source of flooding. C Zones may have local, shallow flooding problems that do not meet the criteria to be mapped as a Special Flood Hazard Area, especially ponding and local drainage problems. |
| Zone X (Unshaded) | Newer Flood Insurance Rate Maps show Zones B and C (see above) as Zone X. The unshaded Zone X corresponds to Zone C. |
Questions about flood hazards or need help with the community rating system (CRS)? Contact us at emergency-management@clearviewgeographic.com; our team is ready to assist with protecting your property!