Williamson County Disaster Risk

Williamson County has a FEMA National Risk Index rating of Relatively Moderate, placing it in the 85th percentile nationally out of 3,144 counties. This composite score reflects the county's overall exposure to natural hazards including floods, wildfires, tornadoes, earthquakes, and hurricanes, weighted by expected annual loss and social vulnerability.

Williamson County is evaluated for five major natural hazard types: earthquake (89th percentile), tornado (89th percentile), flooding (88th percentile), hurricane (41th percentile), wildfire (40th percentile). The highest-risk hazard is earthquake at the 89th percentile nationally. These scores are derived from FEMA's National Risk Index, which analyzes expected annual loss, social vulnerability, and community resilience for each hazard type.

Williamson County's composite risk percentile is 85th, compared to the Tennessee state average of 53th percentile. The state's overall risk rating is Relatively Low. This means Williamson County faces higher natural disaster risk than the typical county in Tennessee.

Yes, Williamson County's earthquake risk is at the 89th percentile nationally. This places it in the top quartile for this hazard type. For flooding specifically, Williamson County is at the 88th percentile.

FEMA's National Risk Index (NRI) calculates risk scores for 18 natural hazard types across all U.S. counties and census tracts. The composite score combines Expected Annual Loss (estimated dollar losses from each hazard), Social Vulnerability (demographic factors affecting disaster impact), and Community Resilience (ability to recover). Percentile scores rank each county against all 3,144 U.S. counties, and risk ratings range from Very Low to Very High.

Williamson County's composite risk score of 85th percentile is above the Tennessee state average of 53th percentile. This elevated risk is driven by earthquake exposure (89th percentile), along with tornado and flooding risk. Geographic location, terrain, climate patterns, and proximity to flood zones or fault lines all influence a county's risk profile.