Sonoma County, CA flood risk explained
Flood hazard in Sonoma County sits at the 99.2th national percentile, well above the national norm for flood hazard; driven by inland rivers and flash flooding rather than the coast — FEMA's model puts a flood event here at about 2.5 times a year. That's a county-wide figure, not a per-address one — FEMA's parcel maps are a live lookup, not a bulk file.
Sonoma County's flood-insurance compliance gap
Out of 3,971 homes FEMA counts inside Sonoma County's mapped flood zone, 1,244 carry the flood policy federal law requires there — 31.3% compliance, short of full coverage. Looking beyond the mandated zone, 1.1% of all residential structures in Sonoma County carry flood coverage voluntarily or otherwise — relevant because most NFIP claims nationally come from outside the mapped SFHA.
Where Sonoma County ranks
Among the 3144 US counties FEMA scores for flood hazard, Sonoma County ranks 31 — 1 being the highest hazard nationally — and 152 by population among all 3144 counties covered here, where 1 is the largest. Sonoma County, California covers 1,575.337 square miles and counts roughly 485,375 residents.
Checking a specific address in Sonoma County
FEMA counts 167,061 residential structures in Sonoma County overall, 1,790 of them carrying some form of NFIP coverage — but a lender or insurer cares about one parcel, not that county total.
Where Sonoma County's figures come from
Every figure on this page traces to a named FEMA dataset, documented in the methodology guide. If you're unsure why any of this insurance requirement exists at all, the SFHA explainer covers it from first principles.