The Flood Insurance Rate Maps (FIRM) show areas within a 100-year flood boundary.  A 100-year flood area does not refer to a flood that occurs every 100 years but refers to a level of flooding that has a 1 percent or greater probability of occurring or being exceeded in any given year.

These 100-year flood areas are termed "Special Flood Hazard Areas (SFHAs). SFHAs are further divided into insurance risk rate zones.  Areas between the 100-year and 500-year flood boundaries are classified as moderate flood hazard areas.  Minimal flood hazard areas represent those remaining areas that lie above the 500-year flood level. Surprisingly, about one-third of all claims paid by the NFIP are for areas identified as minimal or moderate risk for flooding, largely the result of inadequate drainage systems.

To determine which flood zone applies to your property, call or visit the local planning and building permit office in your area or, contact an insurance agent.  You may also order a flood map from FEMA for a nominal fee by calling (800) 358-9616 or by visiting FEMA's web site.

Flood Zone Classifications

The SFHAs are divided into the following flood hazard zones (insurance risk rate zones). The V and A zones have the highest risk of flooding.  Earlier flood maps included B and C zones which were considered as minimal-risk zones but those zones have been phased out and relabeled as X zones on current FEMA flood maps.

V zones

V zones are the most hazardous of the Special Flood Hazard Areas. They usually include the first row of beachfront properties and those properties that are at particular risk from wave velocity  i.e., storm waves — hence the V designation.  Because detailed hydraulic analyses have not been performed, no base flood elevations or depths are shown on the FIRM maps. Flood insurance for these properties is mandated and will usually cost in excess of $1,000 per year.

• Zones VE and V1-30 along coasts are subject to inundation by the 100-year flood with velocity (wave action) likely.  Base flood elevations are shown within these zones.  (Zone VE is used on new and revised maps in place of  the V1-30 zones.)

A zones

A zones are the second most volatile Special Flood Hazard Area (SFHA). These zones are usually located adjacent to a lake, river, stream or other water course and are subject to rising waters.  Flood insurance is also mandatory in most all A zones.  Premiums will range $595 per year or higher due to the risk potential.

Also included are AE, AH, AO, AR, and A99 designations, named for the way in which they might be flooded.

• Zone A  -  subject to inundation by the 100-year flood, no base flood elevations shown,  mandatory flood insurance applies.
• Zones AE and A1-30  -  subject to 100-year flood, base flood elevations are shown, mandatory flood insurance applies.  (On new maps, Zone AE is used in place of Zones A1-30.)
• Zone AH  -   subject to 100-year shallow flooding (average depths between one and three feet), base flood elevations are shown, mandatory insurance applies.
• Zone AO  -  subject to 100-year shallow flooding (usually sheet flow on sloping terrain, 1 to 3 foot average depth),  mandatory insurance applies. 
• Zone A99  -  subject to inundation by the 100-year flood, will be protected by a federal flood protection system when construction has reached specified statutory progress toward completion, no base flood elevations are shown, mandatory flood insurance applies.

X zones

X zones are considered minimal-risk areas and flood insurance is not mandatory.  Premiums may be as low as $306 per year with some areas qualifying for a preferred risk policy.  On older maps, B and C zones have been relabeled as X zones.

• Zones X, B, and C  -  areas of moderate or minimal hazard from flooding, buildings in these zones could be flooded as a result of severe, concentrated rainfall aggravated by inadequate drainage systems.   (The failure of a local drainage system increases risk). Flood insurance is available in participating communities but is not a requirement in these zones.

D zones

D zones represents areas where flooding is possible. Flood insurance is available in participating communities but these areas have not been studied.