How much flood risk does DeKalb County actually carry?
DeKalb County lands at the 83th percentile of FEMA's National Risk Index for flooding, "Relatively Moderate" territory — a middling flood hazard by national standards — with the hazard driven by inland rivers and flash flooding rather than the coast — FEMA's model puts a flood event here at about 1.1 times a year. County-wide, not parcel-specific: FEMA's real flood-zone map is queried live, never shipped as a download.
Who actually carries the flood insurance FEMA requires
Homes with a federally backed mortgage inside DeKalb 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, 20.5% of them do — 107 active policies against 521 structures FEMA counts in that zone, leaving a real compliance gap. Across all residential structures in DeKalb County, not just the ones FEMA mandates, 0.5% carry an NFIP policy — most flood damage nationally happens outside the mapped high-risk zone, so that broader number matters too.
How DeKalb County compares nationally
DeKalb County sits at rank 557 of 3144 counties on FEMA's flood hazard scale (1 is worst) and rank 616 of 3144 by population (1 is biggest). DeKalb County, Illinois covers 631.337 square miles and counts roughly 101,335 residents.
Checking a specific address in DeKalb County
FEMA counts 30,780 residential structures in DeKalb County overall, 152 of them carrying some form of NFIP coverage — but a lender or insurer cares about one parcel, not that county total.
More on how this number was built
The methodology guide shows exactly which FEMA and Census tables feed DeKalb 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.