How much flood risk does Lyman County actually carry?
Lyman County lands at the 29.1th percentile of FEMA's National Risk Index for flooding, "Very Low" territory — among the lowest flood hazard in the country — 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.
Lyman County's flood-insurance compliance gap
Lyman County is one of the counties where FEMA's own denominator for mandated flood-zone structures is missing, so no compliance rate is shown rather than a guessed one — the data quality guide covers how common this is. Across all residential structures in Lyman 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.
Where Lyman County ranks
Lyman County sits at rank 2284 of 3144 counties on FEMA's flood hazard scale (1 is worst) and rank 2905 of 3144 by population (1 is biggest). Lyman County, South Dakota covers 1,642.285 square miles and counts roughly 3,721 residents.
What to do next if you own or are buying in Lyman County
Across all of Lyman County's 1,506 residential structures, 2 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 Lyman County's numbers. See the data quality guide for why Lyman County, like hundreds of other counties, doesn't get a clean compliance percentage.