Methodology

FEMA National Risk Index

The NRI is a dataset from FEMA that identifies communities most at risk for 18 natural hazards. It uses expected annual loss, social vulnerability, and community resilience to calculate an overall risk score for each county.

Risk Ratings

FEMA assigns ratings based on percentile rankings:

• Very High — Top 10% (90th+ percentile)
• Relatively High — 75th-90th percentile
• Relatively Moderate — 40th-75th percentile
• Relatively Low — 15th-40th percentile
• Very Low — Bottom 15%

18 Hazard Types

Avalanche, Coastal Flooding, Cold Wave, Drought, Earthquake, Hail, Heat Wave, Hurricane, Ice Storm, Landslide, Lightning, Riverine Flooding, Strong Wind, Tornado, Tsunami, Volcanic Activity, Wildfire, Winter Weather.

Expected Annual Loss

The dollar amount a county can expect to lose each year from a given hazard, calculated from historical data and exposure analysis.