Is Jefferson County, IA in a flood zone?
FEMA's National Risk Index puts Jefferson County's flood hazard at the 20.4th percentile nationally — among the lowest flood hazard in the country — 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. This describes the county, not any one street — FEMA only publishes exact parcel zones through a live map service.
Mandatory flood insurance compliance in Jefferson County
Homes with a federally backed mortgage inside Jefferson 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, 0% of them do — 0 active policies against 35 structures FEMA counts in that zone, leaving a real compliance gap. Across all residential structures in Jefferson 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.
How Jefferson County compares nationally
Jefferson County sits at rank 2543 of 3144 counties on FEMA's flood hazard scale (1 is worst) and rank 2050 of 3144 by population (1 is biggest). About 15,781 people live in Jefferson County, Iowa, spread over 435.524 square miles.
Checking a specific address in Jefferson County
4 of Jefferson County's 7,956 residential structures carry flood coverage of some kind, per FEMA's latest count — useful context, not a substitute for checking one parcel.
More on how this number was built
The methodology guide shows exactly which FEMA and Census tables feed Jefferson 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.