Defining the Special Flood Hazard Area (SFHA)
In the world of flood insurance, the Special Flood Hazard Area (SFHA) is the land area covered by the floodwaters of the base flood. This is the area where the National Flood Insurance Program's (NFIP) floodplain management regulations must be enforced and where the mandatory purchase of flood insurance applies for federally backed mortgages.
Understanding these zones is critical for passing the complete Flood exam guide. An SFHA is defined as an area that has a one percent annual chance of being inundated by floodwaters. This is often referred to as the "base flood" or the "one-hundred-period flood," though the latter term is often misunderstood as only occurring once every century. In reality, it represents a statistical probability that exists every single year.
SFHA Risk and Probability
Zone A: Inland and Riverine Hazards
Zone A is the most common SFHA designation found on a Flood Insurance Rate Map (FIRM). These areas are subject to rising waters from rivers, lakes, or streams. Because these areas are not subject to coastal wave action, the primary hazard is inundation rather than velocity.
- Zone AE: These are areas where the Base Flood Elevation (BFE) has been determined through rigorous hydraulic analysis.
- Zone AH: Areas characterized by shallow flooding (usually ponding) with average depths between one and three feet.
- Zone AO: Areas of shallow flooding (usually sheet flow on sloping terrain) with average depths between one and three feet.
- Zone AR: Areas that result from the decertification of a previously applicable flood protection system that is currently being restored.
- Zone A99: Areas to be protected from the one percent annual chance flood event by a Federal flood protection system under construction.
When preparing for the exam, remember that any zone starting with the letter 'A' is considered high-risk and falls within the SFHA. You can test your knowledge of these specific zones with our practice Flood questions.
Zone A vs. Zone V: Key Differences
| Feature | Zone A (Inland) | Zone V (Coastal) |
|---|---|---|
| Primary Hazard | Rising water/Inundation | Velocity/Wave action |
| Wave Height | Less than 3 feet | 3 feet or higher |
| Rating Complexity | Standard | Higher due to structural risk |
| SFHA Status | Yes | Yes |
Zone V: Coastal High Hazard Areas
Zone V (and its variants like VE) identifies the Coastal High Hazard Area. These are the portions of the SFHA extending from offshore to the inland limit of a primary frontal dune along an open coast. They are subject to high-velocity waters, including hurricane surges and significant wave action.
Construction in Zone V is subject to much stricter standards than in Zone A. For insurance rating purposes, the presence of waves three feet or higher is the technical threshold that separates a Zone A from a Zone V designation. In Zone VE, BFEs have been specifically calculated, and these elevations must be used to determine insurance premiums and building requirements.
The Mandatory Purchase Requirement
Under federal law, any structure located within an SFHA (Zones A or V) must be covered by flood insurance if the mortgage is secured by a federally regulated or insured lender. This requirement remains in effect for the entire duration of the loan. If a map revision moves a property from a non-SFHA (Zone X) into an SFHA, the lender is required to notify the borrower that they must obtain flood insurance within 45 days.
Non-SFHA Designations: Zones B, C, and X
While the focus of this article is the SFHA, the exam will often ask you to differentiate high-risk zones from moderate-to-low risk zones. Zones B, C, and X are located outside the SFHA.
- Zone X (shaded): Areas of moderate flood hazard, usually the area between the limits of the 1% and 0.2% annual chance floods.
- Zone X (unshaded): Areas of minimal flood hazard, which are the areas outside the 0.2% annual chance flood.
- Zone C/B: Older map designations that have largely been replaced by Zone X but may still appear on legacy documents.
It is a common misconception that "out of the flood zone" means "no risk." Statistics show that a significant percentage of flood claims occur in these moderate-to-low risk zones.