Sonoma, CA Environmental Rules: Flood Elevation Requirements (2026)
Key Facts
- Governing chapter
- SMC Ch. 14.25, Floodplain Management Regulations
- Adopting ordinance
- Ordinance 11-2022
- Default BFE, no data available
- 2 feet above highest adjacent grade
- Large-site trigger
- >50 lots or >5 acres requires BFE study
- Manufactured home floor elevation
- At or above base flood elevation
- General building elevation source
- Adopted California Building Standards Code, not Ch. 14.25
Summary
Where a City of Sonoma property's FIRM does not show a base flood elevation, the floodplain administrator can require an engineer-prepared study or, absent contrary evidence, set the base flood elevation at two feet above the highest adjacent grade at the site.
Where flood hazard areas are delineated on the FIRM and base flood elevation data have not been provided, the floodplain administrator is authorized to: A. Require the applicant to include base flood elevation data prepared by a qualified CA licensed civil engineer in accordance with currently accepted engineering practices. ... ... C. Where base flood elevation and floodway data are not available from another source, where the available data are deemed by the floodplain administrator to not reasonably reflect flooding conditions, or where the available data are known to be scientifically or technically incorrect or otherwise inadequate: ... ... 2. Specify that the base flood elevation is two feet above the highest adjacent grade at the location of the development, provided there is no evidence indicating flood depths have been or may be greater than two feet.
Official source re-checked September 8, 2026: no newer edition of the code had been published (publisher’s edition: current through Ordinance 13-2025, passed December 3, 2025).
Full Breakdown
480). Not every parcel in the City of Sonoma has a mapped base flood elevation. 270 governs approximate Zone A areas, where flood hazard areas are delineated on the FIRM but no base flood elevation data have been provided. In that situation, the floodplain administrator may require the applicant to submit base flood elevation data prepared and sealed by a qualified California-licensed civil engineer; may obtain and provide data from a federal or state agency or another source, or require the applicant to do so; or, where no other data are available or the available data are inadequate, either require an engineer's study or specify that the base flood elevation is two feet above the highest adjacent grade at the site, provided there is no evidence that flood depths have been or may be greater than two feet.
270(B) before the project can be approved. 620). 490), so a freeboard figure for ordinary buildings sits in the adopted building code, not in this chapter's text.
Violations & Fines
SMC 14.25.440 makes any development in a flood hazard area undertaken without a required permit, or not in full compliance with Chapter 14.25 or a permit condition, a violation of the chapter and grounds for enforcement. SMC 14.25.460 provides that any building, structure or land in violation may be declared a public nuisance and abated under applicable city code, and the floodplain administrator can pursue any other remedy available under the Sonoma Municipal Code, including suspension or revocation of the permit under SMC 14.25.240.
Frequently Asked Questions
What if my City of Sonoma parcel's FIRM shows no base flood elevation?
Does the City of Sonoma set a freeboard number above base flood elevation for ordinary buildings?
Can a manufactured home sit below the base flood elevation in the City of Sonoma?
Sources & Official References
Other rules in Sonoma
California rules heatmap·Compare Sonoma to another location·View the California environmental rules overview
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Flood Elevation Requirements in Nearby Cities
How other cities in Sonoma County handle flood elevation requirements.