The floodplain on Flood Insurance Rate Maps is identified as a Special Flood Hazard Area (SFHA). The SFHA is an area that could be inundated by a flood event with a 1 percent chance of reaching or exceeding base flood elevations in any given year. The 1 percent annual chance flood is also referred to as the base flood and you may also hear and see the term 100-year flood, however, see the below information about that term and the misconception associated with it.
“100-year Flood” Misconception – People sometimes hear the phrase “100-year” flood and think a flood happens only once in one hundred years. That old adage is not true. The Special Flood Hazard Area is an area that has a 1 percent chance, or a 1 in 100 chance, of a flood happening in any given year. That means a flood could happen this year and again the next year. It has nothing to do with calendar years. The phrase “1 percent annual chance flood” is more accurate.
X Zone Information – The X zone (also known as “low–risk flood zone”) is an area outside of the Special Flood Hazard Area. It’s important to know that just because an area is designated as X zone does not mean that the area will never flood. Floods don’t read flood maps. Everyone lives in a flood zone — it’s just a question of whether you live in a low, moderate, or high-risk area. Go to https:www.floodsmart.gov/flood-map-zone/find-yours for more information.
Special Flood Hazard Area (SFHA)
The land area that could be covered by the floodwaters of the base flood is where the NFIP’s floodplain management regulations must be enforced and where the mandatory purchase of flood insurance applies for federally backed mortgages. The requirement also extends to private mortgage companies backed by the FDIC or other federal agencies. Therefore, many private mortgage companies also require flood insurance on properties in the SFHA.
| ZONE | EXPLANATION |
| 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 flood insurance purchase requirements and floodplain management standards apply. (In unincorporated Lee County, the county has estimated BFEs in these areas.) |
| AE | Areas subject to inundation by the 1 percent annual chance flood event determined by detailed methods. Base Flood Elevations (BFEs) are shown. Mandatory flood insurance purchase requirements and floodplain management standards apply. |
| AH | Areas subject to inundation by 1 percent annual chance shallow flooding (usually areas of ponding) where average depths are between one and three feet. Base Flood Elevations (BFEs) derived from detailed hydraulic analyses are shown in this zone. Mandatory flood insurance purchase requirements and floodplain management standards apply. |
| AO | Areas subject to inundation by 1 percent annual chance shallow flooding (usually sheet flow on sloping terrain) where average depths are between 1and 3 feet. Average flood depths derived from detailed hydraulic analyses are shown in this zone. Mandatory flood insurance purchase requirements and floodplain management standards apply. Some Zone AO areas have been designated in areas with high flood velocities such as alluvial fans and washes. Communities are encouraged to adopt more restrictive requirements for these areas. |
| AR | Areas that result from the decertification of a previously accredited flood protection system that is determined to be in the process of being restored to provide base flood protection. Mandatory flood insurance purchase requirements and floodplain management standards apply. |
| A99 | Areas subject to inundation by the 1 percent annual chance flood event, but which will ultimately be protected upon completion of an under-construction Federal flood protection system. These are areas of special flood hazard where enough progress has been made on the construction of a protection system, such as dikes, dams, and levees, to consider it complete for insurance rating purposes. Zone A99 may only be used when the flood protection system has reached specified statutory progress toward completion. No Base Flood Elevations (BFEs) or depths are shown. Mandatory flood insurance purchase requirements and floodplain management standards apply. |
| V | Areas along coasts subject to inundation by the 1 percent annual chance flood event with additional hazards associated with storm-induced waves. Because detailed hydraulic analyses have not been performed, no Base Flood Elevations (BFEs) or flood depths are shown. Mandatory flood insurance purchase requirements and floodplain management standards apply. |
| VE, V1-30 | Areas subject to inundation by the 1 percent annual chance flood event with additional hazards due to storm-induced velocity wave action. Base Flood Elevations (BFEs) derived from detailed hydraulic analyses are shown. Mandatory flood insurance purchase requirements and floodplain management standards apply. |
| ZONE | EXPLANATION |
| X (shaded), B | An area of moderate flood hazard that is determined to be outside the Special Flood Hazard Area between the limits of the base flood and the 0.2 percent annual chance (or 500-year) flood. |
| X (unshaded), C | An area of minimal flood hazard that is determined to be outside the Special Flood Hazard Area and higher than the elevation of the 0.2 percent annual chance (or 500-year) flood. |
Zones outside the SFHA (floodplain)
Moderate flood hazard areas, labeled Zone B or Zone X (shaded) are also shown on the FIRM but are not considered part of the Special Flood Hazard Area. 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).