Johnson County, IA flood risk explained
Flood hazard in Johnson County sits at the 79.8th national percentile, a middling flood hazard by national standards; driven by inland rivers and flash flooding rather than the coast — FEMA's model puts a flood event here at about 2 times a year. County-wide, not parcel-specific: FEMA's real flood-zone map is queried live, never shipped as a download.
Johnson County's flood-insurance compliance gap
9.5% of the homes FEMA requires to carry flood insurance in Johnson County — those inside the mapped Special Flood Hazard Area — actually have a policy in force: 178 policies against 1,871 mandated structures, which means a meaningful share of legally-required coverage simply isn't there. Looking beyond the mandated zone, 0.7% of all residential structures in Johnson County carry flood coverage voluntarily or otherwise — relevant because most NFIP claims nationally come from outside the mapped SFHA.
Johnson County against the rest of the country
Among the 3144 US counties FEMA scores for flood hazard, Johnson County ranks 663 — 1 being the highest hazard nationally — and 438 by population among all 3144 counties covered here, where 1 is the largest. About 160,080 people live in Johnson County, Iowa, spread over 612.997 square miles.
Checking a specific address in Johnson County
Across all of Johnson County's 54,675 residential structures, 360 carry an NFIP policy today — a county-wide count that still can't tell you one address's own mapped zone.
Where Johnson 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.