Maricopa County, AZ: flood risk, in FEMA's own numbers
On FEMA's National Risk Index, Maricopa County scores at the 99.9th percentile for flood hazard, rated "Very High" — among the highest flood hazard in the country. The hazard here is driven by inland rivers and flash flooding rather than the coast — FEMA's model puts a flood event here at about 8.5 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.
Maricopa County's flood-insurance compliance gap
Out of 20,901 homes FEMA counts inside Maricopa County's mapped flood zone, 6,086 carry the flood policy federal law requires there — 29.1% compliance, short of full coverage. Looking beyond the mandated zone, 0.6% of all residential structures in Maricopa County carry flood coverage voluntarily or otherwise — relevant because most NFIP claims nationally come from outside the mapped SFHA.
How Maricopa County compares nationally
Among the 3144 US counties FEMA scores for flood hazard, Maricopa County ranks 5 — 1 being the highest hazard nationally — and 4 by population among all 3144 counties covered here, where 1 is the largest. Maricopa County, Arizona covers 9,202.021 square miles and counts roughly 4,673,096 residents.
Checking a specific address in Maricopa County
Across all of Maricopa County's 1,510,831 residential structures, 8,889 carry an NFIP policy today — a county-wide count that still can't tell you one address's own mapped zone.
Where Maricopa 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.