St. Clair County, MI

Supports FEMA checklist item B1-a Hazard identification

16 of the 18 National Risk Index hazards apply here.

Not applicable to this county per NRI, with no federal declaration and no Storm Events record since 1996: avalanche and volcanic activity. That is the evidence for leaving them out of the plan.

Highest expected annual loss (NRI, modeled): Inland Flooding, Cold Wave and Tornado.

Not covered by NRI (local data needed): dam failure (incl. upstream dams); levee failure; flash flood as its own subtype; ice jams; debris flows; erosion (riverine and coastal); land subsidence and sinkholes; expansive soils.

The state hazard mitigation plan also lists hazards for this county; FEMA asks the plan to explain any hazard it leaves out.

Supports FEMA checklist item B1-b Hazard location

• Coastal Flooding and Inland Flooding: the FEMA Flood Insurance Rate Map (FIRM) is the required location source for flooding. See the FEMA Flood Map Service Center (https://msc.fema.gov) for this county.
• Cold Wave, Drought, Hail, Heat Wave, Ice Storm, Lightning, Strong Wind and Winter Weather: affects the whole county; national data give no location within it.
• Earthquake, Hurricane, Landslide, Tornado, Tsunami and Wildfire vary within the county; the packet lists the highest-rated census tracts for each.

Supports FEMA checklist item B1-c Hazard extent

Storm Events records for 13 of the 21 NOAA event-type groups mapped to the 18 hazards, with the scale, observed range and worst recorded event for each; the others say which local data are needed.

Worst recorded tornado, hail and thunderstorm wind (the three event types on record since the 1950s; the packet has every group):

• Hail: 2.75 in hail, 2000-07-14
• Thunderstorm Wind: 78 kt (90 mph), measurement type not recorded, Thunderstorm Wind, 1975-06-04
• Tornado: F4 tornado, 1953-05-21, 10 mi path length (whole path, pre-1996), 1,760 yd wide, $2,500,000 property (pre-1996 NOAA value, recorded in damage ranges); crops not recorded (1953 dollars), 2 direct deaths, 68 direct injuries

Supports FEMA checklist item B1-d Previous occurrences

Federal declarations for this area: 12 declarations covering 8 separate hazard incidents counted in this packet; each with type, dates and county Public Assistance dollars.

New since the last plan (approved 2022-08-30): none.

3 statewide declarations listed separately.

Hazards with no Storm Events record and no federal declaration are stated as such (7 of 18).

Storm Events history: 594 records (notable ones in the PDF, all of them in the Excel file).

Supports FEMA checklist item B1-e Probability of future events

FEMA annualized frequency (modeled) for each hazard, with a descriptor from a scale defined in the packet.

• Highly likely: Hail, Lightning, Strong Wind and Winter Weather
• Likely: Cold Wave, Heat Wave, Ice Storm, Inland Flooding and Tornado
• Possible: Coastal Flooding, Drought, Hurricane and Landslide
• Unlikely: Earthquake and Wildfire

Historical frequency by intensity band (tornado, hail, wind): 9 bands from Storm Events.

Supports FEMA checklist item B1-f Hazards that vary across jurisdictions

Range of census tract risk scores within the area for 16 of the 18 hazards (50 tracts; rated tracts only).

33 jurisdictions: plan clock, repeat-flood count, Public Assistance dollars and event records naming the place (starting figures from federal data).

County Public Assistance in B1-d also includes applicants filed under the county that are not matched to a jurisdiction row here (for example county offices and boards filed under their own names, such as a sheriff's office or a conservation board, and state agencies, special districts and nonprofits), so the jurisdiction rows add up to less.

Supports FEMA checklist items B2-a and B2-b Vulnerability and potential impacts

The packet's table gives county-level starting figures; the plan describes impacts for each jurisdiction and its own assets.

Storm Events damage since 2022-08-30: $77,000 in county-coded records (38 records); $100,000 reported for the zone (7 zone records). Data through 2026-06-30; nominal dollars.

Local data needed

To gather:

• Critical facilities and lifelines per hazard
• A problem statement per jurisdiction per hazard
• Changes in development in hazard-prone areas since the last approval, or a statement of none (E1-a)
• Future assets

Supports FEMA checklist item B2-a Vulnerability (county context)

Population 160,353; building value $34,294,624,496 and agriculture value $104,159,716 (total, not at risk).

National Risk Index rating Relatively Moderate; social vulnerability Relatively Low; community resilience Very High.

Supports FEMA checklist item B2-c Repetitive loss properties

Repetitive-loss properties, FMA definition (44 CFR 77.2): 1 repetitive loss, 4 severe repetitive loss. NFIP insurance definition: 73 and 4.

Mitigated 1; insured 18; NFIP data as of 2026-08-02. Counts by occupancy group and for each jurisdiction are in the packet.