Flood Zone Descriptions: Flood Zone X
All of Palo Alto that is not in a Special Flood Hazard Area is in "ZONE X", which is described as an area of moderate risk of flooding (roughly speaking, outside the 100-year flood but inside the 500-year flood limits), or, for A0 zones, where the 100-year flood will be less than a foot deep. Thus, all of Palo Alto has been determined to be subject to some risk of flooding, and it is inaccurate to say that a given property is "not in a flood zone" simply because it is not in a Special Flood Hazard Area.
The special floodplain construction rules are not applicable to structures in an "X" Zone, and federal regulations do not require that flood insurance be purchased to protect an equity loan on structures in an "X" Zone. But flood insurance is available for structures in "X" zones, and at rather attractive prices. FEMA states that some one-third of its claims payments for flood damage are for structures that are not within a Special Flood Hazard Area.
A structure can be removed from a Special Flood Hazard Area and changed to an "X" Zone designation by means of a FEMA-issued Letter of Map Amendment or Letter of Map Revision (LOMA or LOMR). For addresses where this has been done, the flood zone is designated as "X" (with the notation "LOMA" or "LOMR" in the comment field) in the look-up lists on this website.
Last Updated: May 31, 2007