Charleston County, SC

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): Hurricane, Earthquake and Inland Flooding.

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 16 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, 2011-05-10
• Thunderstorm Wind: 83 kt (96 mph) estimated gust, Thunderstorm Wind, 2022-04-05
• Tornado: F3 tornado, 1960-09-11, 8.8 mi path length (whole path, pre-1996), 100 yd wide, $2,500,000 property (pre-1996 NOAA value, recorded in damage ranges); crops not recorded (1960 dollars), 10 direct injuries

Supports FEMA checklist item B1-d Previous occurrences

Federal declarations for this area: 27 declarations covering 17 separate hazard incidents counted in this packet; each with type, dates and county Public Assistance dollars.

New since the last plan (approved 2024-03-20): EM-3632-SC, EM-3619-SC and EM-3606-SC.

2 statewide declarations listed separately.

Hazards with no Storm Events record and no federal declaration are stated as such (4 of 18).

Storm Events history: 1,677 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: Coastal Flooding, Hail, Inland Flooding, Lightning and Strong Wind
• Likely: Drought, Heat Wave, Hurricane, Ice Storm, Landslide, Tornado, Wildfire and Winter Weather
• Possible: Cold Wave
• Unlikely: Earthquake

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 (98 tracts; rated tracts only).

18 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 2024-03-20: $92,000 in county-coded records (114 records); $177,000 reported for the zone (17 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 407,722; building value $96,535,065,240 and agriculture value $28,818,205 (total, not at risk).

National Risk Index rating Relatively High; 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): 79 repetitive loss, 228 severe repetitive loss. NFIP insurance definition: 1,245 and 177.

Mitigated 45; insured 821; NFIP data as of 2026-08-02. Counts by occupancy group and for each jurisdiction are in the packet.