Rock County, WI: flood risk, in FEMA's own numbers
On FEMA's National Risk Index, Rock County scores at the 87.6th 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 2.1 times a year. County-wide, not parcel-specific: FEMA's real flood-zone map is queried live, never shipped as a download.
Rock County's flood-insurance compliance gap
Homes with a federally backed mortgage inside Rock County's mapped high-risk flood zone (the Special Flood Hazard Area, or SFHA) are legally required to carry an NFIP flood policy. In practice, 32.7% of them do — 173 active policies against 529 structures FEMA counts in that zone, leaving a real compliance gap. Looking beyond the mandated zone, 0.4% of all residential structures in Rock County carry flood coverage voluntarily or otherwise — relevant because most NFIP claims nationally come from outside the mapped SFHA.
Where Rock County ranks
Among the 3144 US counties FEMA scores for flood hazard, Rock County ranks 408 — 1 being the highest hazard nationally — and 425 by population among all 3144 counties covered here, where 1 is the largest. Rock County, Wisconsin is home to about 165,461 people across 718.168 square miles of land.
Checking a specific address in Rock County
Across all of Rock County's 52,484 residential structures, 221 carry an NFIP policy today — a county-wide count that still can't tell you one address's own mapped zone.
Where Rock 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.