Base Flood: The flood having a 1% chance of being equaled or exceeded in any given year, also known as the "100-year" or "1% chance" flood. The base flood is a statistical concept used to ensure that all properties subject to the National Flood Insurance Program are protected to the same degree against flooding.
BFE: Base flood elevation. The elevation of the base of 100-year flood.
SFHA: Special Flood Hazard Area. The base floodplain delineated on a Flood Insurance Rate Map. The SFHA is mapped as Zone A. The SFHA may not encompass all of the community’s flood problems.
The SFHA shown on a community’s FIRM.
There are 7 types of A Zones.
Area of moderate flood hazard usually depicted on FIRMs 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 area protected by levees and base floodplains of little hazard, such as those with average depths of less than 1 foot.
Area of minimal flood hazard, usually depicted on FIRMs as above the 500-year flood level of the primary source of flooding. C Zones may have local, shallow flooding problems. B and C Zones may have flooding that does not meet the criteria to be mapped as a SPHA, especially ponding and local drainage problems.
Area of undetermined but possible flood hazard.
Newer FIRMs show Zones B and C as Zone X. The shaded Zone X corresponds to Zone B and the unshaded Zone X corresponds to Zone C.