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Permit Sonoma

Building Division

Floodplains and Floodways

Flood Map Services

The Federal Emergency Management Agency's (FEMA) Flood Insurance Rate Maps (FIRMs or FIRM-ettes) are used to determine if properties are located within Special Flood Hazard Areas. Permit Sonoma provides Flood Zone Map Determination services upon request.

Permit Sonoma staff can also provide Community Acknowledgement Forms for Letters of Map Amendments (LOMA) for Flood Insurance Studies (FIS) and National Flood Insurance Program Flood Insurance Rate Maps (FIRM or FIRM-ettes).

A LOMA results from an administrative procedure that involves the review of scientific or technical data from an Elevation Certificate submitted by the owner or lessee of property who believes the property has incorrectly been included in a designated Special Flood Hazard Area (SFHA). A LOMA, which is submitted to FEMA, amends the currently effective FEMA map and establishes that a specific property is not located in an SFHA.

Elevation Certificates

Elevation Certificates provide elevation information on structures. Permit Sonoma may have an elevation certificate on record for your property. If not, and you need to obtain one, will need to contract a Civil Engineer or Licensed Land Surveyor. The elevation Certificate must show Lowest Adjacent Grade next to the structure.


The County of Sonoma’s F1 Floodway Combining Districts provide land use regulation for properties situated in floodways, to safeguard against the effects of bank erosion, channel shifts, increased runoff or other threats to life and property and to implement the provisions of the general plan public safety element. The F1 district applies to properties that lie within the floodway as shown on the most recent Federal Emergency Management Agency (FEMA) maps.

The County of Sonoma’s F2 Floodplain Combining Districts are in place to provide protection from hazards and damage which may result from flood waters. This F2 district applies to properties that lie within the 100 year flood hazard area as shown on the most recent FEMA maps.


The County's floodplain and floodway regulations are derived from the Federal Emergency Management Agency (FEMA) National Flood Insurance Program Regulations (NFIP), which mapped and defined the primary floodplain and floodway. The following regulations address requirements for development within floodplain and floodway areas.