Summary
Plan status as of 2026-09-30: Approved, expires 2029-11-13. Plan: Williamson County (FEMA plan 109784), approved 2024-11-14.
Since the plan was approved on 2024-11-14: 3 new hazard declarations (2 incidents) and 83 NOAA Storm Events records; details under "What changed since your last plan".
Highest expected annual loss (FEMA National Risk Index, modeled total; see B1-a): Inland Flooding ($56,972,085 a year), Cold Wave ($13,411,043) and Tornado ($11,550,093).
The tables that follow are organized by the items of FEMA's Local Mitigation Plan Review Tool, Element B (B1-a to B2-c); each heading says which item its tables support.
Plan clock
- Status:
- Approved, expires 2029-11-13
- Plan:
- Williamson County (FEMA plan 109784)
- Approved:
- 2024-11-14
- Days to expiry:
- 1,140
What changed since your last plan (approved 2024-11-14)
- New federal declarations:
- 3 new hazard declarations (2 incidents): EM-3625-TN (Severe Storms, Straight-Line Winds, Tornadoes, and Flooding), EM-3635-TN (Severe Winter Storm), DR-4898-TN (Severe Winter Storm)
- Storm Events records since approval:
- 83 records (data through 2026-06-30)
- Repetitive loss now:
- FMA RL 10, SRL 23 (44 CFR 77.2); any definition: 86
- Repeat-flood change:
- this release sets the baseline count.
Sources: 1, 2, 4, 6 (numbered list at the end)
Plan status for every jurisdiction listed in this county
Source: 1
| Jurisdiction | Type | Status | Plan | Approved | Expires | Days to expirynegative = days since expiry | Notes |
|---|---|---|---|---|---|---|---|
| Williamson County (unincorporated area) | Unincorporated | Approved, expires 2029-11-13 | Williamson County (FEMA plan 109784) | 2024-11-14 | 2029-11-13 | 1,140 | this jurisdiction approved 2024-11-27 |
| Brentwood city | City | Approved, expires 2029-11-13 | Williamson County (FEMA plan 109784) | 2024-11-14 | 2029-11-13 | 1,140 | |
| Fairview city | City | Approved, expires 2029-11-13 | Williamson County (FEMA plan 109784) | 2024-11-14 | 2029-11-13 | 1,140 | this jurisdiction approved 2025-01-06 |
| Franklin city | City | Approved, expires 2029-11-13 | Williamson County (FEMA plan 109784) | 2024-11-14 | 2029-11-13 | 1,140 | this jurisdiction approved 2025-04-29 |
| Nolensville town | Town | Approved, expires 2029-11-13 | Williamson County (FEMA plan 109784) | 2024-11-14 | 2029-11-13 | 1,140 | this jurisdiction approved 2025-01-10 |
| Spring Hill city | City | Approved, expires 2029-11-20 | Maury County (FEMA plan 110137) | 2024-11-21 | 2029-11-20 | 1,147 | Also approved under plan 109784 (Williamson County, expires 2029-11-13). FEMA's plan status map shows one plan per jurisdiction and may show one of these; this packet uses the approved plan that expires last. this jurisdiction approved 2025-01-15 |
| Thompson's Station town | Town | Approved, expires 2029-11-13 | Williamson County (FEMA plan 109784) | 2024-11-14 | 2029-11-13 | 1,140 | this jurisdiction approved 2025-01-06 |
| Franklin Special School District | School/School District | Approved, expires 2029-11-13 | Williamson County (FEMA plan 109784) | 2024-11-14 | 2029-11-13 | 1,140 | this jurisdiction approved 2025-05-13 |
| Williamson County School District | School/School District | Approved, expires 2029-11-13 | Williamson County (FEMA plan 109784) | 2024-11-14 | 2029-11-13 | 1,140 | this jurisdiction approved 2024-11-26 |
State plan status and tribal plans in this state: see the state page.
Supports FEMA checklist item B1-a: hazard identification
Hazards NRI does not cover (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 18 National Risk Index hazards, ranked by expected annual loss (EAL)
Sources: 5, 6
| Rank by EAL | Hazard | NRI risk rating | EAL rating | EAL buildingsmodeled dollars per year | EAL agriculturemodeled dollars per year | Cost of expected deaths and injuriesFEMA's dollar value per year, not property damage | EAL total (see note)modeled dollars per year | Storm Events records, 1996 to 2026-06-30count | Storm Events coverage note |
|---|---|---|---|---|---|---|---|---|---|
| 1 | Inland Flooding | Relatively Moderate | Relatively Moderate | $55,777,582 | $2,140 | $1,192,363 | $56,972,085 | 97 | |
| 2 | Cold Wave | Relatively High | Relatively High | $1,487 | $6,704 | $13,402,852 | $13,411,043 | 1 | |
| 3 | Tornado | Relatively Moderate | Relatively High | $7,077,812 | $2,155 | $4,470,126 | $11,550,093 | 19 | |
| 4 | Earthquake | Relatively Low | Relatively Moderate | $6,412,546 | n/a | $2,070,978 | $8,483,524 | Storm Events does not record earthquakes. | |
| 5 | Strong Wind | Relatively High | Relatively High | $286,610 | $5,981 | $3,079,218 | $3,371,808 | 414 | Includes 7 High Wind and 8 Strong Wind records (NOAA non-thunderstorm wind types, outside NRI's Strong Wind definition). |
| 6 | Heat Wave | Relatively Low | Relatively Moderate | $1,042 | $171 | $1,775,926 | $1,777,140 | 4 | |
| 7 | Ice Storm | Relatively High | Relatively High | $878,876 | n/a | $131,195 | $1,010,072 | 2 | |
| 8 | Winter Weather | Relatively Moderate | Relatively High | $71,932 | $1 | $396,999 | $468,932 | 66 | |
| 9 | Lightning | Relatively Low | Relatively Moderate | $130,795 | n/a | $337,026 | $467,821 | 31 | |
| 10 | Hail | Relatively Low | Relatively Low | $321,339 | $686 | $9,666 | $331,692 | 184 | |
| 11 | Drought | Relatively Low | Relatively Low | n/a | $77,213 | n/a | $77,213 | 29 | |
| 12 | Hurricane | Very Low | Very Low | $48,669 | $5,495 | $1,237 | $55,402 | 0 | No recorded events in Storm Events since 1996 (data through 2026-06-30). |
| 13 | Wildfire | Very Low | Very Low | $40,245 | $10 | $4,410 | $44,664 | 0 | No recorded events in Storm Events since 1996 (data through 2026-06-30). |
| 14 | Landslide | Very Low | Very Low | $1,481 | n/a | $1,677 | $3,157 | 0 | No recorded events in Storm Events since 1996 (data through 2026-06-30). |
Total = buildings + agriculture + population equivalence; FEMA values each expected death (or 10 injuries) at $13.7 million (2024 dollars).
NRI risk rating combines expected annual loss with social vulnerability and community resilience; EAL rating rates expected annual loss alone. Both compare this county with all U.S. counties.
Local data needed: state and local wildfire and landslide records (Storm Events records these hazards only in part).
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.
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
Affects the whole county (national data give no location within it): Cold Wave, Drought, Hail, Heat Wave, Ice Storm, Lightning, Strong Wind and Winter Weather.
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.
Hazards that vary within the county: highest-rated census tracts
Source: 5
| Hazard | Highest-rated census tractsNRI risk rating, score 0 to 100 |
|---|---|
| Earthquake | tract 503.04 (Relatively Moderate, 87.9); tract 509.07 (Relatively Moderate, 84.1); tract 503.07 (Relatively Moderate, 83.8) |
| Hurricane | tract 511 (Very Low, 44.6); tract 501.03 (Very Low, 42.3); tract 506.04 (Very Low, 39.9) |
| Landslide | tract 505.02 (Relatively Low, 93.2); tract 512.03 (Relatively Low, 92.8); tract 511 (Relatively Low, 87.9) |
| Tornado | tract 511 (Very High, 94.9); tract 506.04 (Relatively High, 89.4); tract 512.06 (Relatively High, 87.0) |
| Wildfire | tract 511 (Relatively Low, 80.5); tract 501.03 (Relatively Low, 73.8); tract 510.02 (Relatively Low, 70.7) |
Up to 3 census tracts per hazard, highest National Risk Index rating first, then highest score; a tract number is the Census tract number (for example 503.04 is Census Tract 503.04). FEMA's Resilience Analysis and Planning Tool maps the National Risk Index for every tract: https://www.fema.gov/emergency-managers/practitioners/resilience-analysis-and-planning-tool
Supports FEMA checklist item B1-c: hazard extent
Extent: scale, observed range and worst recorded event per hazard
Sources: 6, 7
| Hazard | Scale | Recordscount and years | Observed range | Worst recorded event | Most damaging (when different) | How it applies to jurisdictions | Note |
|---|---|---|---|---|---|---|---|
| Cold/Wind Chill, Extreme Cold/Wind Chill | wind chill | 1 record, 2022 (1 zone-level) | 1 day; 1 with a recorded value | 1 consecutive day, 2022-12-23, zone-level | Countywide (zone-level records). | ||
| Frost/Freeze (outside NRI's Cold Wave definition) | crop damage | 0 | |||||
| Drought | U.S. Drought Monitor scale (D0 to D4) | 29 records, 2007 to 2026 (29 zone-level) | 14 days to 214 days (median 61 days); 10 with a recorded value | 214 days (7 months), 2007-05-01 to 2007-11-30, a run of 7 consecutive Storm Events drought records, zone-level | Countywide (zone-level records). | Storm Events enters a drought at D2 or worse east of the Rockies and D3 or worse from the Rockies west (NWS Instruction 10-1605); NRI drought counts D3 and D4 only. | |
| Earthquake | Modified Mercalli (local data) | 0 | Storm Events does not record earthquakes; the USGS earthquake catalog is the source. | ||||
| Hail | hail size (inches) | 197 records, 1961 to 2025 | 0.75 in to 3 in (median 1 in); 197 with a recorded value | 3 in hail, 2025-05-20; same size also recorded on 2024-05-26, 2025-05-20 | Hail, 2024-05-26, $100,000 property; $0 crops (2024 dollars) | Event records naming jurisdictions in the plan: Franklin city (39 records), Fairview city (18 records), Nolensville town (11 records), Thompson's Station town (11 records), Brentwood city (1 record). | |
| Excessive Heat, Heat | heat index (in event narratives) | 4 records, 2010 to 2025 (4 zone-level) | 1 day to 2 days (median 1 day); 3 with a recorded value | 2 consecutive days, 2025-07-29 to 2025-07-30, zone-level | Countywide (zone-level records). | ||
| Hurricane, Tropical Storm, Tropical Depression | Saffir-Simpson | 0 | Storm Events files every zone of a storm's episode under the storm's type; flooding from the storm is filed as Flood or Flash Flood records. | ||||
| Ice Storm | Sperry-Piltz ice scale (local data) | 2 records, 2010 to 2013 (2 zone-level) | Ice Storm, 2010-01-29, $25,000 property; crops not reported (2010 dollars); NWS zone TNZ059 | Countywide (zone-level records). | |||
| Flash Flood, Flood, Lakeshore Flood | damage and flood days (flood depth: FIRM) | 97 records, 1996 to 2025 (4 zone-level) | Flood, 2010-05-02, $10,000,000 property; $1,000 crops (2010 dollars) | Event records naming jurisdictions in the plan: Nolensville town (12 records), Franklin city (10 records), Fairview city (8 records), Thompson's Station town (4 records). Zone-level records (4) apply countywide. | Flood depth: see the FEMA Flood Insurance Rate Map. Storm Events damage is often $0 or blank for floods, major ones included; FEMA Public Assistance by declaration (B1-d) shows which floods cost the most. | ||
| Debris Flow | none (count and damage only) | 0 | |||||
| Lightning | annualized frequency (the measure FEMA's Local Mitigation Planning Handbook names) | 31 records, 1998 to 2024 | Lightning, 2010-10-24, $1,750,000 property; crops not reported (2010 dollars) | Event records naming jurisdictions in the plan: Franklin city (5 records), Fairview city (4 records), Nolensville town (2 records). | Storm Events lists lightning with damage or casualties. | ||
| High Wind and Strong Wind (outside NRI's Strong Wind definition) | wind speed (kt and mph) | 15 records, 2001 to 2025 (15 zone-level) | 35 kt (40 mph) to 55 kt (63 mph) (median 45 kt (52 mph)); 15 with a recorded value | 55 kt (63 mph) estimated gust, High Wind, 2013-01-30; NWS zone TNZ059 | High Wind, 2023-03-03, $1,000,000 property; $0 crops (zone total, 2023 dollars) | Countywide (zone-level records). | |
| Thunderstorm Wind | wind speed (kt and mph) | 430 records, 1960 to 2026 | 43 kt (49 mph) to 90 kt (104 mph) (median 52 kt (60 mph)); 393 with a recorded value | 90 kt (104 mph) estimated gust, Thunderstorm Wind, 2003-05-05 | Thunderstorm Wind, 2020-05-03, $703,420 property; $0 crops (2020 dollars) | Event records naming jurisdictions in the plan: Franklin city (57 records), Fairview city (48 records), Nolensville town (28 records), Thompson's Station town (10 records), Brentwood city (3 records), Spring Hill city (1 record). | |
| Tornado | Enhanced Fujita (Fujita before Feb 2007) | 26 records, 1963 to 2025 | F/EF0 to F/EF4 (median F/EF0); 26 with a recorded value | F4 tornado, 1988-12-24, 6 mi path length (whole path, pre-1996), 150 yd wide, $25,000,000 property; crops not recorded (1988 dollars), 1 direct death, 7 direct injuries | Event records naming jurisdictions in the plan: Franklin city (4 records), Nolensville town (2 records), Thompson's Station town (1 record). | Before 1996 a tornado is listed once, under the county where it began, with its whole path's rating and length; from 1996 on, each county lists its own segment. Length is not used to rank tornadoes (see Methods). | |
| Wildfire | acres burned (local data) | 0 | |||||
| Winter Storm, Heavy Snow, Blizzard, Lake-Effect Snow, Winter Weather, Sleet | none in data (snowfall: local data) | 66 records, 1996 to 2026 (66 zone-level) | Winter Storm, 2015-02-16, $100,000 property; $0 crops (2015 dollars); NWS zone TNZ059 | Countywide (zone-level records). |
In event narratives only (local data needed): wind chill, temperature, heat index, ice thickness, acres burned and snow depth; any physical measure of debris flow and lightning.
Storm Events records are more complete after 1996; before 1996 only Tornado (from 1950), Hail and Thunderstorm Wind (from 1955) exist. Zone-level records from zones that no NWS zone-county file places in this county (mostly before 2020) are not counted here (the Methods page explains the zone matching).
Dollars are nominal (as reported), labeled with the year; not adjusted for inflation.
Supports FEMA checklist item B1-d: previous occurrences
Federal declarations for this county: 16 declarations covering 12 separate hazard incidents counted in this packet (declarations for the same incident count once; non-natural and evacuation-only declarations are not counted).
Federal disaster declarations for this county
Sources: 1, 2, 3
| Declared | Incident began | FEMA number | Type | Title | Mapped hazard | County Public Assistancefederal share obligated, nominal dollars | Flags | Notes |
|---|---|---|---|---|---|---|---|---|
| 2026-02-06 | 2026-01-22 | DR-4898-TN | Major disaster | Severe Winter Storm | Winter Weather | $7,790,668.74 | new since last plan; within last 5 years | |
| 2026-01-24 | 2026-01-22 | EM-3635-TN | Emergency | Severe Winter Storm | Winter Weather | no Public Assistance recorded | new since last plan; within last 5 years | same incident as DR-4898 |
| 2025-04-02 | 2025-04-02 | EM-3625-TN | Emergency | Severe Storms, Straight-Line Winds, Tornadoes, and Flooding | Inland Flooding; Strong Wind; Tornado | no Public Assistance recorded | new since last plan; within last 5 years | |
| 2021-05-08 | 2021-03-25 | DR-4601-TN | Major disaster | Severe Storms, Tornadoes, and Flooding | Tornado (primary); also designated: Inland Flooding | $553,973 | ||
| 2020-04-02 | 2020-01-20 | DR-4514-TN | Major disaster | COVID-19 Pandemic | Non-natural, not counted | $1,241,608.08 | ||
| 2020-03-13 | 2020-01-20 | EM-3473-TN | Emergency | COVID-19 | Non-natural, not counted | no Public Assistance recorded | same incident as DR-4514 | |
| 2010-05-04 | 2010-04-30 | DR-1909-TN | Major disaster | Severe Storms, Flooding, Straight-Line Winds, and Tornadoes | Inland Flooding; Strong Wind; Tornado | $3,606,169.50 | ||
| 2008-02-07 | 2008-02-05 | DR-1745-TN | Major disaster | Severe Storms, Tornadoes, Straight-Line Winds, and Flooding | Inland Flooding; Strong Wind; Tornado | $534,571.02 | ||
| 2005-09-05 | 2005-08-29 | EM-3217-TN | Emergency | Hurricane Katrina Evacuation | Hurricane: evacuation support, not a local hazard event; not counted | $85,829.83 | ||
| 2003-05-08 | 2003-05-04 | DR-1464-TN | Major disaster | Severe Storms, Tornadoes, and Flooding | Inland Flooding; Tornado | $714,788.86 | ||
| 1999-05-12 | 1999-05-05 | DR-1275-TN | Major disaster | Severe Storms, Tornadoes and Flooding | Inland Flooding; Tornado | $232,978.46 | ||
| 1998-04-20 | 1998-04-16 | DR-1215-TN | Major disaster | Severe Storms, Tornadoes and Flooding | Inland Flooding; Tornado | PA not declared for this county | ||
| 1994-02-28 | 1994-02-09 | DR-1010-TN | Major disaster | Severe Winter Ice Storm,Flash Flooding | Ice Storm; Inland Flooding; Winter Weather | no Public Assistance recorded | ||
| 1979-05-07 | 1979-05-07 | DR-585-TN | Major disaster | Severe Storms, Tornadoes & Flooding | Inland Flooding; Tornado | no Public Assistance recorded | ||
| 1975-03-22 | 1975-03-22 | DR-459-TN | Major disaster | Severe Storms & Flooding | Inland Flooding | no Public Assistance recorded | ||
| 1974-04-04 | 1974-04-04 | DR-424-TN | Major disaster | Tornadoes | Tornado | no Public Assistance recorded |
School districts and special districts in this county: $367,381.83 (included in the county total above). Public Assistance matched by applicant name to the school districts and special districts FEMA lists as plan participants in this county. They have no row of their own in the jurisdiction table, so their total is listed here. These dollars are already included in the county PA column of the declarations table (the FEMA record places each applicant in this county), so this line is not added to it.
County Public Assistance: applicants the FEMA record places in this county, including any state agencies FEMA files there; statewide rows are listed on the state page; federal share obligated, nominal dollars.
Statewide declarations
Source: 2
| Declared | Incident began | FEMA number | Type | Title | Mapped hazard |
|---|---|---|---|---|---|
| 1963-03-27 | 1963-03-27 | DR-151-TN | Major disaster | Severe Storms & Flooding | Inland Flooding |
FEMA recorded these with designated area Statewide and no county, so they are listed on every county page in the state and not counted with county rows. Local data needed: whether each one affected this county.
Public Assistance not placed in any Tennessee county: 5 rows, $12,113,670.26; listed on the Tennessee state page.
Source: 3
Previous occurrences by hazard, with explicit no-event rows
Sources: 2, 6, 7
| Hazard | Storm Events records, all years on file(years in the Period column) | Since plan approvalrecords | In the 12 months before plan approvalrecords | Last 5 yearsrecords | Declared incidents, all yearsseparate disasters | Declared since approvalseparate disasters | Period | Statement |
|---|---|---|---|---|---|---|---|---|
| Cold Wave | 1 | 0 | 0 | 1 | 0 | 0 | 1996 to 2026-06-30 | |
| Drought | 29 | 3 | 5 | 15 | 0 | 0 | 1996 to 2026-06-30 | |
| Earthquake | 0 | 0 | 0 | 0 | 0 | 0 | Storm Events does not record earthquakes; the USGS earthquake catalog is the source. | |
| Hail | 197 | 43 | 18 | 71 | 0 | 0 | 1955 to 2026-06-30 | |
| Heat Wave | 4 | 2 | 0 | 3 | 0 | 0 | 1996 to 2026-06-30 | |
| Hurricane | 0 | 0 | 0 | 0 | 0 | 0 | 1996 to 2026-06-30 | No recorded events, 1996 to 2026-06-30, NOAA NCEI Storm Events |
| Ice Storm | 2 | 0 | 0 | 0 | 1 | 0 | 1996 to 2026-06-30 | |
| Inland Flooding | 97 | 10 | 0 | 16 | 10 | 1 | 1996 to 2026-06-30 | |
| Landslide | 0 | 0 | 0 | 0 | 0 | 0 | 1996 to 2026-06-30 | No recorded events, 1996 to 2026-06-30, NOAA NCEI Storm Events |
| Lightning | 31 | 0 | 2 | 4 | 0 | 0 | 1996 to 2026-06-30 | |
| Strong Wind | 445 | 22 | 11 | 89 | 3 | 1 | 1955 to 2026-06-30 | Includes 7 High Wind and 8 Strong Wind records. |
| Tornado | 26 | 1 | 0 | 2 | 9 | 1 | 1950 to 2026-06-30 | |
| Wildfire | 0 | 0 | 0 | 0 | 0 | 0 | 1996 to 2026-06-30 | No recorded events, 1996 to 2026-06-30, NOAA NCEI Storm Events |
| Winter Weather | 66 | 2 | 1 | 8 | 2 | 1 | 1996 to 2026-06-30 |
Notable Storm Events records
Sources: 1, 6, 7
| Date | Event type | Magnitude or extent | Damagenominal dollars | Deaths, injuriesdirect only | Location | Flags | Why listed |
|---|---|---|---|---|---|---|---|
| 2025-07-29 | Excessive Heat | $0 property; $0 crops (zone total, 2025 dollars) | 0, 0 | NWS zone TNZ059 (WILLIAMSON), zone-level | new since last plan; within last 5 years | B1-c worst recorded: Excessive Heat, Heat | |
| 2025-05-20 | Hail | 3 in | $0 property; $0 crops (2025 dollars) | 0, 0 | DOUGLAS | new since last plan; within last 5 years | B1-c worst recorded: Hail |
| 2022-12-23 | Extreme Cold/Wind Chill | $0 property; $0 crops (zone total, 2022 dollars) | 0, 0 | NWS zone TNZ059 (WILLIAMSON), zone-level | within last 5 years | B1-c worst recorded: Cold/Wind Chill, Extreme Cold/Wind Chill | |
| 2022-10-12 | Thunderstorm Wind | 50 kt (58 mph) estimated gust | $10,000 property; $0 crops (2022 dollars) | 1, 0 | FOREST HOME | within last 5 years | deaths or injuries recorded |
| 2020-05-03 | Thunderstorm Wind | 56 kt (64 mph) estimated gust | $0 property; $0 crops (2020 dollars) | 1, 0 | HARPETH | deaths or injuries recorded | |
| 2015-02-16 | Winter Storm | $100,000 property; $0 crops (zone total, 2015 dollars) | 0, 0 | NWS zone TNZ059 (WILLIAMSON), zone-level | B1-c worst recorded: Winter Storm, Heavy Snow, Blizzard, Lake-Effect Snow, Winter Weather, Sleet | ||
| 2013-01-30 | High Wind | 55 kt (63 mph) estimated gust | $10,000 property; crops not reported (zone total, 2013 dollars) | 0, 0 | NWS zone TNZ059 (WILLIAMSON), zone-level | B1-c worst recorded: High Wind and Strong Wind | |
| 2010-10-24 | Lightning | $1,750,000 property; crops not reported (2010 dollars) | 0, 0 | MALLORYS | B1-c worst recorded: Lightning | ||
| 2010-05-02 | Flood | $10,000,000 property; $1,000 crops (2010 dollars) | 0, 0 | NOLENSVILLE | B1-c worst recorded: Flash Flood, Flood, Lakeshore Flood | ||
| 2010-01-29 | Ice Storm | $25,000 property; crops not reported (zone total, 2010 dollars) | 0, 0 | NWS zone TNZ059 (WILLIAMSON), zone-level | B1-c worst recorded: Ice Storm | ||
| 2003-05-05 | Thunderstorm Wind | 90 kt (104 mph) estimated gust | $206,000 property; crops not reported (2003 dollars) | 0, 0 | FAIRVIEW | B1-c worst recorded: Thunderstorm Wind | |
| 1988-12-24 | Tornado | F4, 6 mi path length (whole path, pre-1996), 150 yd wide | $25,000,000 property; crops not recorded (1988 dollars) | 1, 7 | location not recorded | deaths or injuries recorded |
The full list is in the Excel file, sheet "B1-d Storm Events history" (898 rows).
Location is the place NOAA recorded, as written in its data; it need not be a jurisdiction in this plan.
Local data needed: state-declared emergencies, from your state emergency management agency (federal data do not include them).
FEMA's declaration data list no tribal or special-area declarations for this state.
Supports FEMA checklist item B1-e: probability of future events
Probability: FEMA annualized frequency and descriptor per hazard
Sources: 5, 6
| Hazard | FEMA annualized frequency (modeled)unit per row | Unit | In plain terms | Descriptor | Descriptor basis | NRI events or days in its record period (hail, wind and tornado are area-weighted, so can be fractional) | NRI period | Location | Note |
|---|---|---|---|---|---|---|---|---|---|
| Cold Wave | 1.16 | event-days per year | about 1.16 days per year | Possible | Storm Events event-days in 1 of 30 years, 1996 to 2025 (3.33%) | 22 | 2005-11-12 to 2024-11-12 (19 years) | countywide | |
| Drought | 9.57 | event-days per year | about 9.57 days per year | Likely | Storm Events event-days in 8 of 30 years, 1996 to 2025 (26.7%) | 385 | 2000 to 2025 (25.25 years; D3 and D4 only) | countywide | |
| Earthquake | 0.00336 | annual probability at a location | chance a given location in the county has at least minor-damage shaking in a year: 0.336% | not shown | modeled | see B1-f | No descriptor (Storm Events does not record earthquakes). | ||
| Hail | 3.5 | events per year | about 3.5 per year | Highly likely | FEMA annualized frequency (modeled) | 133.0 (modeled) | 1986 to 2023 (38 years) | countywide | |
| Heat Wave | 4.95 | event-days per year | about 4.95 days per year | Likely | Storm Events event-days in 3 of 30 years, 1996 to 2025 (10%) | 81 | 2005-11-12 to 2024-11-12 (19 years) | countywide | |
| Hurricane | 0.0161 | events per year | about 1 in 62 years | Possible | FEMA annualized frequency (modeled) | 6 | 1851 to 2024 (Atlantic) | see B1-f | NRI counts hurricane and tropical storm tracks passing within storm-force wind range; federal declarations are in B1-d. |
| Ice Storm | 0.618 | event-days per year | about 0.618 days per year | Possible | Storm Events event-days in 2 of 30 years, 1996 to 2025 (6.67%) | 42 | 1946-12-31 to 2014-02-12 (67 years) | countywide | |
| Inland Flooding | 2.18 | event-days per year | about 2.18 days per year | Likely | Storm Events event-days in 26 of 30 years, 1996 to 2025 (86.7%) | 61 | 1996 to 2023 (28 years) | see B1-f | |
| Landslide | 0.864 | events per year (modeled) | about 0.86 per year | Likely | FEMA annualized frequency (modeled) | not shown | modeled | see B1-f | |
| Lightning | 60.5 | days per year with a strike | about 60.5 days per year | Highly likely | FEMA annualized frequency (modeled) | not shown | 1995 to 2023 (29 years; CONUS) | countywide | |
| Strong Wind | 6.11 | events per year | about 6.11 per year | Highly likely | FEMA annualized frequency (modeled) | 233 | 1986 to 2023 (38 years) | countywide | |
| Tornado | 0.51 | events per year | about 0.51 per year | Likely | FEMA annualized frequency (modeled) | not shown | 1950 to 2023 (EF2+); 1986 to 2023 (EF0-1) | see B1-f | |
| Wildfire | 0.000047 | annual probability at a location | chance a given location in the county burns in a year: 0.0047% | Storm Events records in 0 of 30 years, 1996 to 2025 (0%) | not shown | modeled | see B1-f | No descriptor: no Storm Events record 1996 to 2025 | |
| Winter Weather | 5.16 | event-days per year | about 5.16 days per year | Likely | Storm Events event-days in 20 of 30 years, 1996 to 2025 (66.7%) | 98 | 2005-11-12 to 2024-11-12 (19 years) | countywide |
FEMA annualized frequency (modeled) is the National Risk Index v1.20 (December 2025) estimate of how often a hazard affects this county in a year; it is not recorded events divided by years, and its unit differs by hazard (events, event-days, or days with a lightning strike per year). For earthquake, wildfire, coastal flooding and tsunami the value is the chance (or number of events) at a location in the county, not across the county, so no "1 in N years" is given and the descriptor comes from Storm Events where it has a record (none for earthquake). The Methods page gives each hazard's method, from FEMA's National Risk Index Technical Documentation v1.20.
Where NRI gives event-days, the descriptor comes from the share of years with a Storm Events record; NRI's source records more events, so the two differ.
Descriptor scale used in this packet (defined per unit)
Sources: 5, 6
| Unit | Descriptor | Definition |
|---|---|---|
| events per year | Highly likely | 1 or more per year |
| events per year | Likely | about once in 1 to 10 years |
| events per year | Possible | about once in 10 to 100 years |
| events per year | Unlikely | less than once in 100 years |
| annual probability | Likely | 10% to under 100% chance in a given year |
| annual probability | Possible | 1% to under 10% chance in a given year |
| annual probability | Unlikely | under 1% chance in a given year |
| event-days (share of years) | Highly likely | event-days recorded in 90% or more of years |
| event-days (share of years) | Likely | event-days recorded in 10% to under 90% of years |
| event-days (share of years) | Possible | event-days recorded in some years but under 10% of years |
| lightning strike-days | Highly likely | cloud-to-ground strikes on 1 or more days per year |
Intensity bands: historical frequency (Storm Events)
Source: 6
| Hazard | Band | Years | Eventscounty-coded records | Years in period | Events per yearevents / years |
|---|---|---|---|---|---|
| Hail | 1.00-1.99 in | 1996 to 2025 | 109 | 30 | 3.63 |
| Hail | 2.00 in+ | 1996 to 2025 | 19 | 30 | 0.633 |
| Thunderstorm Wind (counted as NRI Strong Wind) | 50-64 kt | 1996 to 2025 | 347 | 30 | 11.6 |
| Thunderstorm Wind (counted as NRI Strong Wind) | 65 kt+ | 1996 to 2025 | 10 | 30 | 0.333 |
| Thunderstorm Wind (counted as NRI Strong Wind) | unmeasured or below 50 kt | 1996 to 2025 | 38 | 30 | 1.27 |
| Tornado | EF0-1 | 1996 to 2025 | 17 | 30 | 0.567 |
| Tornado | EF2-3 | 1996 to 2025 | 2 | 30 | 0.0667 |
| Tornado | EF4-5 | 1996 to 2025 | 0 | 30 | 0 |
| Tornado | unrated (EFU) | 1996 to 2025 | 0 | 30 | 0 |
The bands show how often events of each severity were recorded in this county, to profile how severe events have been (FEMA's probability item asks for the range of intensities).
Hail smaller than 1 inch is not counted: on 2010-01-05 the National Weather Service raised its severe-hail threshold from 3/4 inch to 1 inch, so smaller reports became less common after 2009 (NWS Service Change Notice 09-52). NRI hail frequency uses a 0.75 inch threshold.
Optional: future conditions. Not a required item in the 2025 FEMA Local Mitigation Planning Policy Guide; some states ask for it. The federal Climate Mapping for Resilience and Adaptation (CMRA) site gives county exposure to future climate conditions (https://resilience.climate.gov/).
Supports FEMA checklist item B1-f: hazards that vary across jurisdictions
Range of census tract risk within the county
Source: 5
| Hazard | Tractsrated of all | NRI risk score, 0 to 100 | Tracts by rating | ||
|---|---|---|---|---|---|
| Min | Median | Max | |||
| Cold Wave | 46 of 46 | 53.6 | 83.3 | 94.6 | Relatively High 31, Relatively Moderate 15 |
| Drought | 20 of 46 | 70.3 | 79.2 | 88.9 | Relatively Low 11, Very Low 9, No Rating 26 |
| Earthquake | 46 of 46 | 43.1 | 74.2 | 87.9 | Relatively Moderate 16, Relatively Low 30 |
| Hail | 46 of 46 | 30.2 | 41.8 | 61.8 | Relatively Low 37, Very Low 9 |
| Heat Wave | 46 of 46 | 9.7 | 38.2 | 65.1 | Relatively Moderate 5, Relatively Low 35, Very Low 6 |
| Hurricane | 46 of 46 | 25.5 | 31.7 | 44.6 | Very Low 46 |
| Ice Storm | 46 of 46 | 59.2 | 77.8 | 92.3 | Relatively High 2, Relatively Moderate 36, Relatively Low 8 |
| Inland Flooding | 46 of 46 | 23.2 | 65.3 | 97.8 | Very High 1, Relatively High 11, Relatively Moderate 20, Relatively Low 14 |
| Landslide | 46 of 46 | 11.7 | 46.9 | 93.2 | Relatively Low 4, Very Low 42 |
| Lightning | 46 of 46 | 15.4 | 37.2 | 60.6 | Relatively Moderate 5, Relatively Low 39, Very Low 2 |
| Strong Wind | 46 of 46 | 49.1 | 79.2 | 92.8 | Relatively High 19, Relatively Moderate 25, Relatively Low 2 |
| Tornado | 46 of 46 | 47.4 | 70.3 | 94.9 | Very High 1, Relatively High 16, Relatively Moderate 28, Relatively Low 1 |
| Wildfire | 46 of 46 | 42.3 | 60.2 | 80.5 | Relatively Low 4, Very Low 42 |
| Winter Weather | 46 of 46 | 48.0 | 74.2 | 89.9 | Relatively High 18, Relatively Moderate 26, Relatively Low 2 |
Drought: Agriculture is all of NRI's expected annual loss for this hazard in the county, so the tract range mostly reflects where crop and livestock value is.
Rated tracts only: No Rating (score 0.0), Not Applicable and Insufficient Data tracts are counted but not used for the minimum, median and maximum.
The score ranks a tract against all U.S. tracts (100 = highest). The rating is FEMA's category for the tract's risk value, computed differently, so the two can disagree.
Frequency data for cold wave, drought, hail, heat wave, ice storm, lightning, strong wind and winter weather are county-wide or coarse (49 km grid or NWS zone), the same for every jurisdiction; the tract range mostly reflects where buildings and people are (crop and livestock value where a line above names agriculture).
Each jurisdiction (starting figures from federal data)
Sources: 1, 3, 4, 6
| Jurisdiction | Type | Plan status | Repetitive lossFMA RL and SRL (44 CFR 77.2); repeat-flood, any definition | Public Assistance to this jurisdictionFEMA records matched by applicant name; federal share obligated, nominal dollars | Event records naming this placeall years; since its plan | Notes |
|---|---|---|---|---|---|---|
| Williamson County (unincorporated area) | Unincorporated | Approved, expires 2029-11-13 | FMA RL 0, SRL 5; any 30 | $3,128,733.45 | 0 total; 0 since its plan | Includes $8,293.17 for declarations not counted as hazard incidents (EM-3217-TN). |
| Brentwood city | City | Approved, expires 2029-11-13 | FMA RL 8, SRL 10; any 31 | $5,891,058.49 | 4 total; 0 since its plan | |
| Fairview city | City | Approved, expires 2029-11-13 | FMA RL 0, SRL 1; any 1 | $2,262,538.19 | 78 total; 4 since its plan | |
| Franklin city | City | Approved, expires 2029-11-13 | FMA RL 2, SRL 7; any 15 | $1,521,073.63 | 115 total; 6 since its plan | Includes $115,354.07 for declarations not counted as hazard incidents (DR-4514-TN, EM-3217-TN). |
| Nolensville town | Town | Approved, expires 2029-11-13 | FMA RL 0, SRL 0; any 8 | $31,148.83 | 55 total; 1 since its plan | Includes $7,463.32 for declarations not counted as hazard incidents (DR-4514-TN). |
| Spring Hill city | City | Approved, expires 2029-11-20 | FMA RL 0, SRL 0; any 1 | no Public Assistance recorded | 1 total; 0 since its plan | Also approved under plan 109784 (Williamson County, expires 2029-11-13). FEMA's plan status map shows one plan per jurisdiction and may show one of these; this packet uses the approved plan that expires last. Whole community, including the part in Maury County; none of its repeat-flood properties are in this county. |
| Thompson's Station town | Town | Approved, expires 2029-11-13 | FMA RL 0, SRL 0; any 0 | no Public Assistance recorded | 26 total; 2 since its plan |
Repetitive-loss counts are for whole NFIP communities, which can extend beyond this county (see the note in B2-c).
School districts and special districts get a plan clock row only.
County Public Assistance in B1-d also includes applicants filed under the county that are not jurisdictions in this plan (for example 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
Local data needed
The table below gives county-level starting figures; the plan describes impacts for each jurisdiction and its own assets.
- 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
County-level starter: exposure, expected annual loss and damage since the plan
Sources: 1, 2, 3, 5, 6, 7
| Hazard | Building exposuremodeled dollars | Agriculture exposuremodeled dollars | Population exposedpeople | EAL buildingsmodeled dollars per year | EAL agriculturemodeled dollars per year | Cost of expected deaths and injuriesFEMA's dollar value per year, not property damage | EAL as % of exposurebuildings; agriculture where noted | Storm Events damage since 2024-11-14county-coded records, property plus crops, nominal dollars | Zone-level damage since planproperty plus crops, reported for the zone | Public Assistance since plannominal dollars; see note | Note |
|---|---|---|---|---|---|---|---|---|---|---|---|
| Cold Wave | $61,392,881,948 | $39,793,160 | 247,523 | $1,487 | $6,704 | $13,402,852 | under 0.0001% | ||||
| Drought | n/a | $19,378,759 | n/a | n/a | $77,213 | n/a | 0.398% (agriculture) | NRI has no building exposure for this hazard; agriculture shown | |||
| Earthquake | $103,160,324,843 | n/a | 247,726 | $6,412,546 | n/a | $2,070,978 | 0.00622% | ||||
| Hail | $61,392,881,948 | $39,793,160 | 247,523 | $321,339 | $686 | $9,666 | 0.000523% | $0 | |||
| Heat Wave | $61,392,881,948 | $39,793,160 | 247,523 | $1,042 | $171 | $1,775,926 | under 0.0001% | $0 | |||
| Hurricane | $61,373,609,441 | $39,704,203 | 247,438 | $48,669 | $5,495 | $1,237 | under 0.0001% | ||||
| Ice Storm | $61,385,588,893 | n/a | 247,445 | $878,876 | n/a | $131,195 | 0.00143% | ||||
| Inland Flooding | $61,321,455,606 | $6,667,684 | 5,094 | $55,777,582 | $2,140 | $1,192,363 | n/a (see note) | $0 | no Public Assistance recorded (1 declaration) | NRI counts the full building value of any census block with some flood loss; this is not the value of buildings in the floodplain. Use local FIRM overlays for B2-a/B2-b. | |
| Landslide | $2,633,633,144 | n/a | 9,442 | $1,481 | n/a | $1,677 | under 0.0001% | ||||
| Lightning | $61,392,881,948 | n/a | 247,523 | $130,795 | n/a | $337,026 | 0.000213% | ||||
| Strong Wind | $61,392,881,948 | $39,793,160 | 247,523 | $286,610 | $5,981 | $3,079,218 | 0.000467% | $165,000 | $5,000 | no Public Assistance recorded (1 declaration) | Storm Events damage since the plan includes 1 zone-level Strong Wind record ($5,000): a NOAA non-thunderstorm wind type, outside NRI's Strong Wind definition. |
| Tornado | $61,392,881,948 | $39,793,160 | 247,523 | $7,077,812 | $2,155 | $4,470,126 | 0.0115% | $25,000 | no Public Assistance recorded (1 declaration) | ||
| Wildfire | $31,171,063,473 | $23,961,259 | 137,525 | $40,245 | $10 | $4,410 | 0.000129% | ||||
| Winter Weather | $61,392,881,948 | $39,793,160 | 247,523 | $71,932 | $1 | $396,999 | 0.000117% | $0 | $7,790,668.74 |
Totals since 2024-11-14 (Storm Events through 2026-06-30): 75 county-coded records, 75 with a damage value recorded (including $0), $190,000; 8 zone-level records, 4 with a damage value recorded (including $0), $5,000 reported for the zone; Public Assistance: $7,790,668.74 on 3 counted declarations, 1 of them with Public Assistance.
FEMA does not split Public Assistance by hazard. A declaration mapped to several hazards is listed under each of them with its full amount, so the per-hazard column does not add up to the total; the unit total counts each declaration once.
NRI computes earthquake exposure on its own basis, so it exceeds the county building value in B2-a.
Supports FEMA checklist item B2-a: vulnerability (county context)
County context
Source: 5
| Measure | Value |
|---|---|
| Population | 247,523 |
| Building value (total, not at risk) | $61,392,881,948 |
| Agriculture value (total, not at risk) | $39,793,160 |
| NRI risk rating (all hazards) | Relatively Moderate |
| Expected annual loss, buildings and agriculture, all hazards | $71,150,972 |
| Expected annual loss, population equivalence, all hazards (NRI values each statistical life at $13.7M; a modeled value of expected deaths and injuries, not property damage) | $26,873,674 |
| Social vulnerability rating | Very Low |
| Community resilience rating | Very High |
| NRI version | December 2025 |
FEMA's all-hazard expected annual loss adds buildings, agriculture and population equivalence; this table gives the property part and the population-equivalence part as separate rows.
Social vulnerability: higher means people are more likely to be harmed and slower to recover. Community resilience: lower means the community is less able to recover. High social vulnerability and low resilience both raise the NRI risk rating.
Supports FEMA checklist item B2-c: repetitive loss properties
Repetitive loss in this county, both definitions
Sources: 1, 4
| Definition | Properties | Severe repetitive loss | Properties |
|---|---|---|---|
| Repetitive loss, FMA definition (44 CFR 77.2) | 10 | Severe repetitive loss, FMA definition (44 CFR 77.2) | 23 |
| Repetitive loss, NFIP insurance definition | 76 | Severe repetitive loss, NFIP insurance definition | 15 |
The state NFIP coordinator's list, the source FEMA's Handbook names, often uses the NFIP insurance definition (second row).
Repeat-flood properties: county total and NFIP communities
Sources: 1, 4
| Scope | RL, FMAproperties | SRL, FMAproperties | RL, NFIPproperties | SRL, NFIPproperties | Any categoryproperties | Mitigatedproperties | Currently insuredproperties |
|---|---|---|---|---|---|---|---|
| County total | 10 | 23 | 76 | 15 | 86 | 8 | 44 |
| of which: Williamson County (unincorporated area) | 0 | 5 | 29 | 4 | 30 | 1 | 14 |
| of which: Brentwood city | 8 | 10 | 27 | 7 | 31 | 3 | 20 |
| of which: Franklin city | 2 | 7 | 10 | 3 | 15 | 4 | 4 |
| of which: Fairview city | 0 | 1 | 1 | 1 | 1 | 0 | 0 |
| of which: Nolensville town | 0 | 0 | 8 | 0 | 8 | 0 | 6 |
| of which: Unknown (community ID Unknown in FEMA data) | 0 | 0 | 1 | 0 | 1 | 0 | 0 |
Repeat-flood properties by jurisdiction in the plan (NFIP community)
Sources: 1, 4
| Jurisdiction | NFIP community ID | RL, FMAproperties | SRL, FMAproperties | RL, NFIPproperties | SRL, NFIPproperties | Any categoryproperties | Mitigatedproperties | Currently insuredproperties | Note |
|---|---|---|---|---|---|---|---|---|---|
| Williamson County (unincorporated area) | 470204 | 0 | 5 | 29 | 4 | 30 | 1 | 14 | |
| Brentwood city | 470205 | 8 | 10 | 27 | 7 | 31 | 3 | 20 | |
| Fairview city | 470242 | 0 | 1 | 1 | 1 | 1 | 0 | 0 | |
| Franklin city | 470206 | 2 | 7 | 10 | 3 | 15 | 4 | 4 | |
| Nolensville town | 470425 | 0 | 0 | 8 | 0 | 8 | 0 | 6 | |
| Spring Hill city | 470278 | 0 | 0 | 1 | 0 | 1 | 0 | 0 | Whole community, including the part in Maury County; none of its repeat-flood properties are in this county. |
| Thompson's Station town | 470424 | 0 | 0 | 0 | 0 | 0 | 0 | 0 |
Counts by occupancy group for each jurisdiction are in the Excel file, sheet "B2-c Jurisdictions".
Jurisdiction rows are whole NFIP communities and need not add up to the county total: a community that extends into another county is counted in full on each jurisdiction row, while the county table counts only its part in this county.
County repeat-flood properties by occupancy group
Sources: 1, 4
| Occupancy group | RL, FMAproperties | SRL, FMAproperties | RL, NFIPproperties | SRL, NFIPproperties | Any categoryproperties | Mitigatedproperties | Currently insuredproperties |
|---|---|---|---|---|---|---|---|
| single-family residential | 10 | 22 | 72 | 14 | 82 | 8 | 43 |
| 2 to 4 unit residential | 0 | 0 | 0 | 0 | 0 | 0 | 0 |
| other residential | 0 | 0 | 0 | 0 | 0 | 0 | 0 |
| non-residential | 0 | 1 | 4 | 1 | 4 | 0 | 1 |
| not reported | 0 | 0 | 0 | 0 | 0 | 0 | 0 |
FEMA's occupancy groups have no institutional class; institutional properties are counted in non-residential or other residential in the table by occupancy group.
FMA RL and FMA SRL are the Flood Mitigation Assistance definitions (44 CFR 77.2), the ones the FEMA Local Mitigation Planning Policy Guide cites. NFIP repetitive loss (the FEMA insurance definition) is 2 or more claims over $1,000 in 10 years, and a property can leave that group once it is mitigated. Also shown: NFIP severe repetitive loss, any category, mitigated and currently insured. The Methods page gives the OpenFEMA field details.
Counts are aggregates of FEMA's public NFIP Multiple Loss Properties file (FEMA's data date 2026-08-02; file version 2026-08-04). No property is identified. County assignment is FEMA's geocode.
In this county 3 properties are FMA repetitive loss but not NFIP repetitive loss, and 69 properties are NFIP repetitive loss but not FMA repetitive loss.
Exact counts; no count suppression.
Sources
Tables cite these sources by number. The full list, for the plan's bibliography (FEMA review item A4-a):
- FEMA, OpenFEMA HazardMitigationPlanStatuses v1, version 2026-09-29T134039Z, pulled 2026-09-30, https://www.fema.gov/api/open/v1/HazardMitigationPlanStatuses (API)
- FEMA, OpenFEMA DisasterDeclarationsSummaries v2, version 2026-09-29T162832Z, pulled 2026-09-30, https://www.fema.gov/api/open/v2/DisasterDeclarationsSummaries (API)
- FEMA, OpenFEMA PublicAssistanceFundedProjectsSummaries v1, version 2026-09-29T150754Z, pulled 2026-09-30, https://www.fema.gov/api/open/v1/PublicAssistanceFundedProjectsSummaries (API)
- FEMA, OpenFEMA NfipMultipleLossProperties v1, version 2026-08-04T164045Z, pulled 2026-09-30, https://www.fema.gov/api/open/v1/NfipMultipleLossProperties (API)
- FEMA, FEMA National Risk Index 1.20.0 (December 2025), county and census tract tables, version 1.20.0, pulled 2026-09-30, https://www.fema.gov/about/reports-and-data/openfema/nri/v120/NRI_Table_Counties.zip (download, 25 MB), https://www.fema.gov/about/reports-and-data/openfema/nri/v120/NRI_Table_CensusTracts.zip (download, 635 MB)
- NOAA NCEI, NOAA NCEI Storm Events Database, details files (csvfiles v1.0), version c20260918, pulled 2026-09-30, https://www.ncei.noaa.gov/pub/data/swdi/stormevents/csvfiles/
- NOAA National Weather Service, NWS county-public forecast zones correlation file, version bp03mr20 to bp16ap26 (11 files; newest bp16ap26), pulled 2026-09-30, https://www.weather.gov/gis/ZoneCounty
- U.S. Census Bureau, Census 2024 Gazetteer, 2020 place by county, CT county-to-cousub crosswalk, version 2024-gazetteer, pulled 2026-09-30, https://www2.census.gov/geo/docs/maps-data/data/gazetteer/2024_Gazetteer/2024_Gaz_counties_national.zip, https://www2.census.gov/geo/docs/maps-data/data/gazetteer/2024_Gazetteer/2024_Gaz_cousubs_national.zip, https://www2.census.gov/geo/docs/maps-data/data/gazetteer/2024_Gazetteer/2024_Gaz_place_national.zip, https://www2.census.gov/geo/docs/maps-data/data/gazetteer/2024_Gazetteer/2024_Gaz_unsd_national.zip, https://www2.census.gov/geo/docs/maps-data/data/gazetteer/2024_Gazetteer/2024_Gaz_elsd_national.zip, https://www2.census.gov/geo/docs/maps-data/data/gazetteer/2024_Gazetteer/2024_Gaz_scsd_national.zip, https://www2.census.gov/geo/docs/reference/codes2020/national_place_by_county2020.txt, https://www2.census.gov/geo/docs/reference/ct_change/ct_cou_to_cousub_crosswalk.xlsx (used to match place names and codes; no table prints its values)
What this packet is and what the plan adds
This packet is the federal data for the plan's risk assessment (the summary on page 1 says how it is organized); the plan and FEMA's review decide whether each item is met.
The plan adds what only the community has: local data on assets, critical facilities, development and each jurisdiction's impacts; local hazard history, including state-declared emergencies; the mitigation strategy; and adoption.
How the federal data are built: National Risk Index values are FEMA's model, not counts of events. Storm Events is more complete from 1996; zone-level records are placed by forecast zone, not by location in the county. Public Assistance for a jurisdiction is matched by applicant name. The Methods page gives every rule and the known edge cases.
OpenFEMA disclaimer
This product uses the Federal Emergency Management Agency's OpenFEMA API, but is not endorsed by FEMA. The Federal Government or FEMA cannot vouch for the data or analyses derived from these data after the data have been retrieved from the Agency's website(s).
Reuse, citation and corrections
Reuse and citation: Hazard Plain text and tables are licensed under Creative Commons Attribution 4.0 International (CC BY 4.0, https://creativecommons.org/licenses/by/4.0/); credit Hazard Plain and the release. The underlying federal data are public domain; OpenFEMA data are also subject to the OpenFEMA terms and conditions.
Cite this: Hazard Plain (2026). Williamson County, TN: risk-assessment baseline packet, release 2026-10 (data as of 2026-09-30; County FIPS 47187). Automated baseline. https://hazardplain.org/tn/47187/ Built from FEMA OpenFEMA, the FEMA National Risk Index and NOAA NCEI Storm Events; source versions in the packet's Sources list.
Corrections: to report an error, name the packet, the table and what your records show. Contact: [email protected]