Is Mercer County, NJ in a flood zone?
FEMA's National Risk Index puts Mercer County's flood hazard at the 97.2th percentile nationally — well above 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 3.6 times a year. That's a county-wide figure, not a per-address one — FEMA's parcel maps are a live lookup, not a bulk file.
Mandatory flood insurance compliance in Mercer County
Out of 1,826 homes FEMA counts inside Mercer County's mapped flood zone, 761 carry the flood policy federal law requires there — 41.7% compliance, short of full coverage. Across all residential structures in Mercer County, not just the ones FEMA mandates, 1.2% carry an NFIP policy — most flood damage nationally happens outside the mapped high-risk zone, so that broader number matters too.
How Mercer County compares nationally
Mercer County sits at rank 98 of 3144 counties on FEMA's flood hazard scale (1 is worst) and rank 195 of 3144 by population (1 is biggest). Mercer County, New Jersey covers 224.482 square miles and counts roughly 392,138 residents.
Checking a specific address in Mercer County
Across all of Mercer County's 107,040 residential structures, 1,294 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 Mercer 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.