St. Clair County, MI: flood risk, in FEMA's own numbers
On FEMA's National Risk Index, St. Clair County scores at the 85.9th percentile for flood hazard, rated "Relatively Moderate" — a middling flood hazard by national standards. The hazard here is driven by inland rivers and flash flooding rather than the coast — FEMA's model puts a flood event here at about 1 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
Out of 6,574 homes FEMA counts inside St. Clair County's mapped flood zone, 1,154 carry the flood policy federal law requires there — 17.6% compliance, short of full coverage. Looking beyond the mandated zone, 2% of all residential structures in St. Clair County carry flood coverage voluntarily or otherwise — relevant because most NFIP claims nationally come from outside the mapped SFHA.
Where St. Clair County ranks
Among the 3144 US counties FEMA scores for flood hazard, St. Clair County ranks 468 — 1 being the highest hazard nationally — and 436 by population among all 3144 counties covered here, where 1 is the largest. St. Clair County, Michigan is home to about 160,308 people across 721.522 square miles of land.
Checking a specific address in St. Clair County
Across all of St. Clair County's 62,457 residential structures, 1,248 carry an NFIP policy today — a county-wide count that still can't tell you one address's own mapped zone.
Where St. Clair 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.