Is Union County, SD in a flood zone?
FEMA's National Risk Index puts Union County's flood hazard at the 47.5th 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 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 Union County
Out of 208 homes FEMA counts inside Union County's mapped flood zone, 54 carry the flood policy federal law requires there — 26% compliance, short of full coverage. Across all residential structures in Union County, not just the ones FEMA mandates, 2.5% carry an NFIP policy — most flood damage nationally happens outside the mapped high-risk zone, so that broader number matters too.
How Union County compares nationally
Union County sits at rank 1712 of 3144 counties on FEMA's flood hazard scale (1 is worst) and rank 1958 of 3144 by population (1 is biggest). Union County, South Dakota is home to about 17,402 people across 460.757 square miles of land.
Checking a specific address in Union County
199 of Union County's 7,883 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 Union 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.