Washtenaw County Disaster Risk

Washtenaw County has a FEMA National Risk Index rating of Relatively Moderate, placing it in the 89th 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.

Washtenaw County is evaluated for five major natural hazard types: tornado (97th percentile), flooding (90th percentile), earthquake (74th percentile), hurricane (48th percentile), wildfire (44th percentile). The highest-risk hazard is tornado at the 97th 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.

Washtenaw County's composite risk percentile is 89th, compared to the Michigan state average of 50th percentile. The state's overall risk rating is Relatively Low. This means Washtenaw County faces higher natural disaster risk than the typical county in Michigan.

Yes, Washtenaw County's tornado risk is at the 97th percentile nationally. This places it in the top quartile for this hazard type. For flooding specifically, Washtenaw County is at the 90th 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.

Washtenaw County's composite risk score of 89th percentile is above the Michigan state average of 50th percentile. This elevated risk is driven by tornado exposure (97th percentile), along with flooding and earthquake risk. Geographic location, terrain, climate patterns, and proximity to flood zones or fault lines all influence a county's risk profile.