How FEMA Measures Natural Hazard Risk

The NRI Formula

Risk = Expected Annual Loss × Social Vulnerability ÷ Community Resilience. This means areas with high expected losses, high social vulnerability, AND low resilience face the greatest risk.

Expected Annual Loss Components

EAL is calculated for each of 18 hazard types using: historical event frequency, building exposure value, population exposure, agricultural exposure, and event impact models. EAL represents what a community should statistically expect to lose per year.

Social Vulnerability Index

Measures how susceptible a community is to harm based on: income levels, education, age demographics, disability rates, language barriers, transportation access, housing type, and healthcare access.

Community Resilience

Measures the ability to prepare for, adapt to, and recover from hazards: economic resilience (employment, housing values), infrastructure (communications, transportation, healthcare), community capital (educational attainment, social cohesion), and institutional capacity (government services, mitigation activities).