Marin County, CA Environmental Rules: Flood Elevation Requirements (2026)
Key Facts
- Enforcing agency
- Dept. of Public Works (floodplain administrator)
- Elevation standard
- Lowest floor at or above base flood elevation
- Zone AO/VO minimum
- 2 ft above highest adjacent grade
- First-offense fine
- Up to $50, escalating to $250
- Variance appeal fee
- $100 to Board of Supervisors
- Base flood defined as
- 1% annual chance ('100-year') flood
Summary
Any new construction or substantial improvement in Marin County's mapped special flood hazard areas must have its lowest floor elevated to or above the base flood elevation, per Marin County Code of Ordinances § 23.09.034. The Department of Public Works, acting as floodplain administrator, reviews every permit in flood-prone unincorporated areas before construction begins.
(c)Elevation and Floodproofing.(1)New construction and substantial improvement of any structure shall have the lowest floor, including basement, elevated to or above the base flood elevation. Nonresidential structures may meet the standards in subparagraph (3) of subsection (c) of this section. Upon completion of the structure, the elevation of the lowest floor, including basement, shall be certified by a registered civil engineer, or licensed land surveyor. Such certification shall be provided to the floodplain administrator.
Official source re-checked September 7, 2026: no newer edition of the code had been published (publisher’s edition: Municipal Code: Supplement 2026 Update 1).
Full Breakdown
030(4), (27)). The elevation of the completed lowest floor must be certified by a registered civil engineer or licensed land surveyor and filed with the floodplain administrator. 034(c)(2) instead requires the lowest floor to sit above the highest adjacent grade, at least as high as the depth number printed on the Flood Insurance Rate Map, or at least two feet if no depth number is shown. 034(c)(3): a watertight structure below the BFE with components able to resist hydrostatic and hydrodynamic loads, certified by a registered engineer or architect.
033 requires the Department of Public Works to review every application for construction, grading, dredging, paving, drilling or manufactured-home placement inside a flood-prone area and to collect the proposed lowest-floor elevation. 033(d)(3)). 033(d)(5)). 038: no fill, new construction or substantial improvement is allowed unless a registered civil engineer certifies it will not raise flood levels during the base flood discharge.
Violations & Fines
Violating Chapter 23.09 is an infraction under § 23.09.050: a fine up to fifty dollars for a first offense, up to one hundred dollars for a second violation of the same rule within a year, and up to two hundred fifty dollars for each further violation, with every day of continued noncompliance charged as a separate offense. The county can also treat the violation as a nuisance and abate it under Chapter 1.05. A structure built without the required elevation certificate is presumed noncompliant under § 23.09.030(40) until the paperwork is produced.
Frequently Asked Questions
Who enforces Marin County's flood elevation rules in the unincorporated area?
Can I get a variance from the elevation requirement?
What if my parcel has no published base flood elevation?
Sources & Official References
Other rules in Marin County
California rules heatmap·Compare Marin County to another location·View the California environmental rules overview
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