Risk-assessment baseline packet (county-level sections from Grand Isle County). Town FIPS 5001367000, Grand Isle County. Release 2026-10, data as of 2026-09-30.
Summary
Plan status as of 2026-09-30: Expired on 2023-07-15. Plan: Town of South Hero, Vermont HAZARD MITIGATION PLAN 2018 (FEMA plan 104992), approved 2018-07-16.
Sections B1-a, B1-b, B1-c, B1-d, B1-e, B2-a and B2-b use Grand Isle County data (county FIPS 50013; each heading says so); the plan clock, B1-f and B2-c are for South Hero town.
Since the plan was approved on 2018-07-16: 6 new hazard declarations (5 incidents) and 92 NOAA Storm Events records (county-level); details under "What changed since your last plan".
Highest expected annual loss (FEMA National Risk Index, modeled total; see B1-a): Inland Flooding ($3,140,357 a year), Strong Wind ($172,409) and Earthquake ($160,717).
The packet's tables are organized by the items of FEMA's Local Mitigation Plan Review Tool, Element B (B1-a to B2-c); the summaries below follow the same order.
What the packet contains
Sections in FEMA checklist order; each heading names the review item its tables support. Full tables are in the downloads above.
Supports FEMA checklist item B1-a Hazard identification
County-level: Grand Isle County.
14 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, coastal flooding, tsunami and volcanic activity. That is the evidence for leaving them out of the plan.
Highest expected annual loss (NRI, modeled): Inland Flooding, Strong Wind and Earthquake.
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
County-level: Grand Isle 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 and Wildfire vary within the county; the packet lists the highest-rated census tracts for each.
- 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.
Supports FEMA checklist item B1-c Hazard extent
County-level: Grand Isle County.
Storm Events records for 10 of the 20 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: 1.75 in hail, 2013-09-11; same size also recorded on 2005-07-22
- Thunderstorm Wind: 70 kt (81 mph) estimated gust, Thunderstorm Wind, 2007-08-16
Supports FEMA checklist item B1-d Previous occurrences
County-level: Grand Isle County (federal declarations, statewide declarations and Storm Events history).
Federal declarations for this area: 18 declarations covering 14 separate hazard incidents counted in this packet; each with type, dates and county Public Assistance dollars.
New since the last plan (approved 2018-07-16): EM-3609-VT, DR-4720-VT, EM-3595-VT, DR-4695-VT, EM-3567-VT, DR-4532-VT, EM-3437-VT and DR-4380-VT.
2 statewide declarations listed separately.
Hazards with no Storm Events record and no federal declaration are stated as such (7 of 18).
Storm Events history: 376 records (notable ones in the PDF, all of them in the Excel file).
Supports FEMA checklist item B1-e Probability of future events
County-level: Grand Isle County.
FEMA annualized frequency (modeled) for each hazard, with a descriptor from a scale defined in the packet.
- Highly likely: Lightning and Winter Weather
- Likely: Cold Wave, Hail, Heat Wave, Ice Storm, Inland Flooding and Strong Wind
- Possible: Hurricane and Landslide
- Unlikely: Tornado
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 14 of the 18 hazards (2 tracts; rated tracts only).
1 jurisdiction: plan clock, repeat-flood count, Public Assistance dollars and event records naming the place (starting figures from federal data).
Supports FEMA checklist items B2-a and B2-b Vulnerability and potential impacts
County-level: Grand Isle County (National Risk Index exposure and expected annual loss; since-plan counts use South Hero town's approval date).
The packet's table gives county-level starting figures; the plan describes impacts for each jurisdiction and its own assets.
Storm Events damage since 2018-07-16: $102,000 in county-coded records (13 records); $662,000 reported for the zone (79 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
- Vermont Flood Ready Atlas and Agency of Natural Resources (ANR) river corridors for town flood and erosion locations.
- The Emergency Relief and Assistance Fund (ERAF) Flood Hazard Summary gives E911 building counts in the Special Flood Hazard Area (SFHA) per town.
- Vermont Dam Inventory for dams in and upstream of the town.
- Vermont Emergency Management (VEM) hazard mitigation planning resources and the 2023 Vermont State Hazard Mitigation Plan.
Supports FEMA checklist item B2-a Vulnerability (county context)
County-level: Grand Isle County.
Population 7,289; building value $2,816,595,456 and agriculture value $23,095,317 (total, not at risk).
National Risk Index rating Very Low; social vulnerability Very Low; community resilience Very High.
Supports FEMA checklist item B2-c Repetitive loss properties
Repetitive-loss properties (Grand Isle County, county-level), FMA definition (44 CFR 77.2): 0 repetitive loss, 0 severe repetitive loss. NFIP insurance definition: 0 and 0.
Mitigated 0; insured 0; NFIP data as of 2026-08-02. Counts by occupancy group and for each jurisdiction are in the packet.