Williamson County, TX flood risk explained
Flood hazard in Williamson County sits at the 91.3th national percentile, a middling flood hazard by national standards; 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. 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
45.8% of the homes FEMA requires to carry flood insurance in Williamson County — those inside the mapped Special Flood Hazard Area — actually have a policy in force: 591 policies against 1,291 mandated structures, which means a meaningful share of legally-required coverage simply isn't there. Looking beyond the mandated zone, 1.1% of all residential structures in Williamson County carry flood coverage voluntarily or otherwise — relevant because most NFIP claims nationally come from outside the mapped SFHA.
How Williamson County compares nationally
Among the 3144 US counties FEMA scores for flood hazard, Williamson County ranks 291 — 1 being the highest hazard nationally — and 96 by population among all 3144 counties covered here, where 1 is the largest. Williamson County, Texas covers 1,115.869 square miles and counts roughly 727,480 residents.
Checking a specific address in Williamson County
1,949 of Williamson County's 177,153 residential structures carry flood coverage of some kind, per FEMA's latest count — useful context, not a substitute for checking one parcel.
Where Williamson 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.