FEMA Flood Insurance Rate Map "L" Series Flood Hazard Zones as used in Pima County

Special Flood Hazard Areas Subject to Inundation by the 1% Annual Chance Flood

The 1% annual flood (100-year flood), also known as the base flood, is the flood that has a 1% chance of being equaled or exceeded in any given year. The Special Flood Hazard Area is the area subject to flooding by the 1% annual chance flood. Areas of Special Flood Hazard in Pima County include Zones A, AE, AH, and AO. The Base Flood Elevation is the water-surface elevation of the 1% annual chance flood.

FEMA FIRM Zone Designation	FIRM Definition	Additional Information
ZONE A	No Base Flood Elevations determined.	The local floodplain jurisdictions may have additional information including Base Flood Elevations.
ZONE AE	Base Flood Elevations determined.
ZONE AH	Flood depths generally between 1 to 3 feet (usually areas of ponding); Base Flood Elevations determined.	In some locations the elevations within channels may be deeper than 3 feet.
ZONE AO 1   ZONE AO 2   ZONE AO 3	Flood depths of 1 to 3 feet (usually sheet flow on sloping terrain); average depths determined. For areas of alluvial fan flooding, velocities also determined.
ZONE AO - ALLUVIAL FAN 1   ZONE AO - ALLUVIAL FAN 2   ZONE AO - ALLUVIAL FAN 3   ZONE AO - ALLUVIAL FAN 4	Same as ZONE AO	Alluvial fan flood zones may also be susceptible to erosion, deposition and channel avulsions.

Other Flood Areas

FEMA FIRM Zone Designation	FIRM Definition	Additional Information
ZONE X - SHADED	Areas of 0.2% annual chance flood; areas of 1% annual chance flood with average depths of less than 1 foot or with drainage areas less than 1 square mile; and areas protected by levees from 1% annual chance flood.
ZONE X - PROTECTED BY LEVEE		Areas protected by levees from the 1% annual chance flood will either be shown as "Provisionally Accredited" or "Accredited". If a "Provisionally Accredited" levee can not be certified, future floodplain mapping will no longer show areas behind the levee as being protected by the 1% annual chance flood.

Other Areas

FEMA FIRM Zone Designation	FIRM Definition	Additional Information
ZONE X	Areas determined to be outside the 0.2% annual chance floodplain.	ZONE X includes areas where the flood hazard has not been mapped by FEMA but may have been mapped by a local jurisdiction; therefore ZONE X does not necessarily mean there are no flood hazards.
ZONE D	Areas in which flood hazards are undetermined,but possible.	Generally federal or tribal lands.

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