Is Washington County, MO in a flood zone?
FEMA's National Risk Index puts Washington County's flood hazard at the 52.6th percentile nationally — below 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 once every 1 years. That's a county-wide figure, not a per-address one — FEMA's parcel maps are a live lookup, not a bulk file.
Washington County's flood-insurance compliance gap
Out of 238 homes FEMA counts inside Washington County's mapped flood zone, 9 carry the flood policy federal law requires there — 3.8% compliance, short of full coverage. Across all residential structures in Washington County, not just the ones FEMA mandates, 0.1% carry an NFIP policy — most flood damage nationally happens outside the mapped high-risk zone, so that broader number matters too.
Where Washington County ranks
Washington County sits at rank 1552 of 3144 counties on FEMA's flood hazard scale (1 is worst) and rank 1660 of 3144 by population (1 is biggest). About 23,583 people live in Washington County, Missouri, spread over 759.866 square miles.
Your street may differ from Washington County's average
Across all of Washington County's 11,276 residential structures, 10 carry an NFIP policy today — a county-wide count that still can't tell you one address's own mapped zone.
More on how this number was built
The methodology guide shows exactly which FEMA and Census tables feed Washington County's numbers. The guide to what the Special Flood Hazard Area actually means explains why the mandatory-insurance rule exists and who it applies to.