San Francisco County, CA flood risk explained
Flood hazard in San Francisco County sits at the 98.6th 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 1.6 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.
Who actually carries the flood insurance FEMA requires
FEMA hasn't published a residential structure count for San Francisco County's mapped flood zone, so a reliable mandatory-compliance percentage can't be computed here — see the data quality guide for why this gap exists for roughly a quarter of US counties. Looking beyond the mandated zone, 0.1% of all residential structures in San Francisco County carry flood coverage voluntarily or otherwise — relevant because most NFIP claims nationally come from outside the mapped SFHA.
Where San Francisco County ranks
Among the 3144 US counties FEMA scores for flood hazard, San Francisco County ranks 50 — 1 being the highest hazard nationally — and 78 by population among all 3144 counties covered here, where 1 is the largest. San Francisco County, California covers 46.685 square miles and counts roughly 827,526 residents.
Your street may differ from San Francisco County's average
204 of San Francisco County's 195,187 residential structures carry flood coverage of some kind, per FEMA's latest count — useful context, not a substitute for checking one parcel.
Where San Francisco County's figures come from
Every figure on this page traces to a named FEMA dataset, documented in the methodology guide. San Francisco County's compliance figure is one of the ones affected by FEMA's incomplete denominator data — the data quality guide explains what that means and how many counties it touches.