Sonoma County, CA Environmental Rules: Flood Zones (2026)

Chapter 7B, Flood Damage Prevention, adopts FEMA's September 6, 2006 Flood Insurance Study and FIRMs by reference (§ 7B-2) and requires a building, grading, or drainage permit before any development begins in a mapped special flood hazard area (§ 7B-5). New construction and substantial improvements of residential structures must have the lowest floor, including basement, elevated at least 12 inches above the base flood elevation; nonresidential structures may instead be floodproofed to that height (§ 7B-11). The chief building official, through the Permit and Resource Management Department, administers permits and can grant variances only on a showing of hardship and minimum necessary relief (§§ 7B-6, 7B-8, 7B-9). This governs unincorporated county land only. Santa Rosa, Petaluma, Rohnert Park, Windsor, Healdsburg, Sebastopol, Cotati, Cloverdale, and the City of Sonoma each enforce their own separate flood ordinances.