The Federal Emergency Management Agency (FEMA) issues Flood Insurance Rate Maps (FIRM) that designate the flood risk for properties throughout a community.  The FIRM designates the flood zone for properties and identifies those properties that are within the Special Flood Hazard Area (SFHA).  Properties in the SFHA are projected to be subject to flooding in the event of the 1% (100-year) flood event and are subject to the City’s Flood Hazard Regulations (Palo Alto Municipal Code Chapter 16.52).  The FIRM is developed at a macroscopic level and cannot distinguish local fluctuations in ground elevations that may change the flood risk to an individual land parcel.  Therefore, FEMA has a map change procedure that allows individual property owners to request a change to the flood zone designation of their parcel based on site-specific topographic information.  The tools of this program are known as Letters of Map Amendment (LOMAs) and Letters of Map Revision (LOMRs).  LOMAs and LOMRs have the effect of removing either a structure, a portion of a property, or an entire property from a Special Flood Hazard Area (SFHA), based on the elevation of the ground.  In effect, the applicant must prove to FEMA's satisfaction that their structure is located on ground high enough that the structure will be on its own little "island" during the 1% flood event (also known as the Base Flood).  The basic difference between a LOMA and a LOMR is that a LOMR is based on a ground elevation created by the addition of fill to the property since the date of the community’s first FIRM (February 15, 1980, for Palo Alto), whereas a LOMA is based on original grades.

Please note that floor elevation is not a factor in removing a structure from the SFHA -- only the appropriate ground elevation is relevant.

FEMA designates the following categories of LOMAs and LOMRs:

Letter of Map Amendment (LOMA):  FEMA verifies that applicant's land, or at least the land immediately adjacent to the structure, is high enough to be above the Base Flood Elevation (BFE).

  • Conditional Letter of Map Amendment (CLOMA):  Same as LOMA, but issued in advance of construction.  When construction is complete, appropriate as-built date must be supplied to FEMA for a permanent LOMA to be issued.


  • Letter of Map Revision Based on Fill (LOMR-F):  Similar to a LOMA, but based on fill added since the first FIRM date.  LOMRs require that the elevation of the lowest floor, including a basement, be above the Base Flood Elevation.
  • Conditional Letter of Map Revision Based on Fill (CLOMR-F):  An advance LOMR, prior to placement of fill; as-built information must be supplied at completion of construction for issuance of a permanent LOMR.
  • Letter of Map Revision (LOMR) and Conditional Letter of Map Revision (CLOMR): Used for larger projects involving fill where more general flood plain boundary changes might be involved. These are not usually applicable to individual small property owners.
  • FEMA will require a number of documents to be submitted as part of the application for a LOMA or LOMR.  Among these documents may be the following:

    • Recorded plat map or property deed (available from the Santa Clara County Recorder's Office).
    • Photocopy of the Flood Insurance Rate Map panel (available at the Development Center).
    • FEMA Property Information form (to be completed by the property owner).
    • FEMA Elevation Information form (to be completed by Licensed Surveyor or Registered Professional Engineer).
    • FEMA Summary of Elevations form (used when more than one lot is involved; to be completed by Licensed Surveyor or Registered Professional Engineer).
    • FEMA Certification of Fill Compaction (for LOMR applications; to be completed by Registered Professional Engineer).
    • FEMA Community Acknowledgement of Requests Involving Fill (for LOMR applications; completed by City of Palo Alto Public Works Engineering).

    It will be necessary to hire a Licensed Surveyor or Registered Professional Engineer to provide some of the documents required for a LOMA/LOMR application.  There are up-front FEMA charges for certain types of applications, although there is currently no fee for a single-lot LOMA.  The LOMA/LOMR forms are available from FEMA online.

    Once a LOMA or LOMR has been obtained, the applicant is relieved of the federal requirement that loans using the structure as collateral be protected by flood insurance, and a refund can be gotten for some current flood insurance premiums paid.  It must be remembered, though, that a LOMA/LOMR only "removes" a structure or property from the 1% flood area -- there is still some remaining risk of flood.  For instance, the structure may still be flooded in an event larger than the 1% event, and a lender may still consider it prudent to require flood insurance.  If the lender still requires flood insurance, however, the premiums will be much lower than before issuance of the LOMA/LOMR.

    Once a LOMA or LOMR has been obtained for a property, that property is no longer subject to the special building regulations contained in Palo Alto Municipal Code Chapter 16.52.  Although LOMAs/LOMRs are issued by FEMA directly to the property owner and they are not official City documents, the City also receives a copy of these documents.  The City keeps an active file of all LOMAs/LOMRs received from FEMA.  For copies of LOMAs/LOMRs, please visit the City’s Development Center at 285 Hamilton Avenue or contact Public Works Engineering at 650-329-2151.

    LOMAs and LOMRs that remove an existing structure from the SFHA are invalidated once the footprint of the structure is enlarged.  In all cases, LOMAs and LOMRs are only valid until the next revision of the FIRM is published, unless they are revalidated by FEMA.  If an existing LOMA/LOMR is invalidated, it will then be necessary for the property owner to ask for a replacement of the LOMA/LOMR based on a new application.  If the revised FIRM or expanded structure footprint does not create a change in the flood conditions for the property, a new LOMA/LOMR will normally be issued. Typically FEMA issues a blanket letter revalidating a list of LOMAs and LOMRs that are considered to be valid in conjunction with the issuance of a revised FIRM.  If you have a LOMA or LOMR and are uncertain as to its validity after a map update, please visit the City’s Development Center at 285 Hamilton Avenue or contact Public Works Engineering at 650-329-2151.

    View the May 18, 2009 LOMA Recertification Letter.

Last Updated: May 31, 2007