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Williamson County, Tennessee

A shallow water table limits basements on 17% of Williamson County's mapped land. Shrink-swell clay limits houses without basements on 8%.

100% of the county is in drought on the October 13, 2026 Drought Monitor map. FEMA's flood data list 275 flood losses here since 2016, 9% of them in buildings with basements. 16% of homes were built before 1980, against 50% nationally; the median home dates from 2002.

Data as of October 13, 2026 · sources

8%

expansive clay: shrink-swell limits slab homes

17%

high water table: limits basements

100%

in drought, October 13, 2026

16%

of homes built before 1980

Soil under Williamson County

Expansive clay (limits slab homes)7.5%
High water table (limits basements)16.6%
Septic fields very limited83.4%
Clay swell (LEP, by area)3.3%
High-swell land (LEP 6%+)9.9%
Mapped soil373,600 acres
Soil seriesShare hereSeries nationally: high water table
Bodine11%0%
Baxter7%n/a
Armour7%n/a
Stiversville7%n/a
Dellrose5%n/a
Mimosa5%n/a
Davidson County: 8%Maury County: 9%Rutherford County: 14%Cheatham County: 19%Marshall County: 10%Dickson County: 12%Hickman County: 10%Bedford County: 23%Williamson County DavidsonMauryRutherfordCheathamMarshallDicksonHickmanBedfordWilliamson
Williamson County (heavy outline) and nearby counties, shaded by high water table share.under 10%10-25%25-40%40-60%60%+

How we count · survey areas TN187 (2025-09-02)

What the numbers mean here

On 17% of Williamson County's mapped land, soil stays saturated within about 6 feet of the surface for part of the year, which is basement depth.

Rain over the 12 months to August 2026: 44.64 in, 8.88 in below the 1991-2020 average year of 53.52 in.

USDA rates 83% of the land very limited for septic absorption fields.

Drought

100% of the county is in drought (D1 or worse) on the October 13, 2026 map. Part of the county was in drought in 25 of the last 52 weeks; the most was 100% of its area, in 15 weeks, most recently on the October 13, 2026 map.

October 21, 2025Share of area in drought, weeklyOctober 13, 2026
Category, October 13, 2026Share of county
D0 abnormally dry or worse100%
D1 moderate drought or worse100%
D2 severe or worse100%
D3 extreme or worse6.9%
D4 exceptional0%

Flood losses since 2016

275 flood losses since 2016, $9.9 million paid. The worst year was 2021, with 198. Foundations of the buildings, where recorded: 9% basements, 14% slabs, 63% crawl spaces, 14% elevated. Median water depth outside the building: 20 in.

YearFlood losses
20160
201728
20183
201910
202021
2021198
20224
20231
20242
20254
2026 to date4

Rain

Average year, 1991-202053.52 in
12 months to August 202644.64 in (-8.88)
202550.57 in (-2.95)
Wettest year since 18951979: 72.86 in
Driest year since 18951941: 33.12 in
Days with 1 inch or more, normal at FRANKLIN SEWAGE PLT (4 mi away)15.2

Homes

Housing units96,921
Median year built2002
Built before 198016%
Built 2000 or later53%
Owner-occupied79%
Median value, owner-occupied$751,900
Single-family detached78%

What repairs cost

Published ranges from cost guides, not quotes. More sources, and where they disagree.

WorkRangeSource
Basement waterproofing, US $3,000 to $10,000 Fixr, February 6, 2026
Sump pump installation, US $800 to $2,000 Fixr, January 31, 2025
Crawl space encapsulation, US $2,000 to $8,000 Fixr, August 29, 2025

Nearby counties

PlaceDistanceExpansive clayHigh water table
Davidson County, TN 20 mi 14% 8%
Maury County, TN 22 mi 8% 9%
Rutherford County, TN 27 mi 21% 14%
Cheatham County, TN 27 mi under 1% 19%
Marshall County, TN 31 mi 21% 10%
Dickson County, TN 31 mi under 1% 12%
Hickman County, TN 32 mi 1% 10%
Bedford County, TN 36 mi 33% 23%

Sources: USDA SSURGO (September 2, 2025) · US Drought Monitor (October 13, 2026) · FEMA NFIP v3 (September 9, 2026) · NOAA (August 2026) · Census ACS 2020-2024. Methods · Data status