Johnson County, Tennessee
USDA's soil survey flags shrink-swell clay on 0% of Johnson County's mapped land and a shallow water table under basements on 1%, both below the national shares of 15% and 29%. None of the county is in drought on the October 13, 2026 Drought Monitor map.
FEMA's flood data list 37 flood losses here since 2016, 25% of them in buildings with basements. 49% of homes were built before 1980, against 50% nationally; the median home dates from 1981.
Data as of October 13, 2026 · sources
expansive clay: shrink-swell limits slab homes
high water table: limits basements
in drought, October 13, 2026
of homes built before 1980
Soil under Johnson County
| Expansive clay (limits slab homes) | 0.0% |
| High water table (limits basements) | 1.4% |
| Septic fields very limited | 94.3% |
| Clay swell (LEP, by area) | 1.3% |
| High-swell land (LEP 6%+) | 0.0% |
| Mapped soil | 193,700 acres |
| Soil series | Share here | Series nationally: expansive clay |
|---|---|---|
| Keener | 14% | n/a |
| Ditney | 12% | n/a |
| Unicoi | 9% | n/a |
| Lonon | 8% | n/a |
| Calvin | 8% | n/a |
| Northcove | 7% | n/a |
How we count · survey areas TN091 (2025-08-28)
What the numbers mean here
Rain over the 12 months to August 2026: 44.15 in, 6.58 in below the 1991-2020 average year of 50.73 in.
USDA rates 94% of the land very limited for septic absorption fields.
With shrink-swell clay on 0% and a shallow water table on 1% of the land, the soil survey points to neither problem across most of Johnson County; conditions still vary lot by lot.
Drought
0% of the county is in drought (D1 or worse) on the October 13, 2026 map. Part of the county was in drought in 39 of the last 52 weeks; the most was 100% of its area, in 29 weeks, most recently on the July 21, 2026 map.
| Category, October 13, 2026 | Share of county |
|---|---|
| D0 abnormally dry or worse | 98.9% |
| D1 moderate drought or worse | 0% |
| D2 severe or worse | 0% |
| D3 extreme or worse | 0% |
| D4 exceptional | 0% |
Flood losses since 2016
37 flood losses since 2016, $1.9 million paid. The worst year was 2024, with 33. Foundations of the buildings, where recorded: 25% basements, 22% slabs, 39% crawl spaces, 14% elevated. Median water depth outside the building: 21 in.
| Year | Flood losses |
|---|---|
| 2016 | 0 |
| 2017 | 1 |
| 2018 | 0 |
| 2019 | 2 |
| 2020 | 0 |
| 2021 | 0 |
| 2022 | 0 |
| 2023 | 1 |
| 2024 | 33 |
| 2025 | 0 |
| 2026 to date | 0 |
Rain
| Average year, 1991-2020 | 50.73 in |
| 12 months to August 2026 | 44.15 in (-6.58) |
| 2025 | 49.87 in (-0.86) |
| Wettest year since 1895 | 2020: 66.87 in |
| Driest year since 1895 | 1925: 34.66 in |
| Days with 1 inch or more, normal at MTN CITY 2 (4 mi away) | 11.5 |
Homes
| Housing units | 8,761 |
| Median year built | 1981 |
| Built before 1980 | 49% |
| Built 2000 or later | 20% |
| Owner-occupied | 78% |
| Median value, owner-occupied | $178,600 |
| Single-family detached | 69% |
What repairs cost
Published ranges from cost guides, not quotes. More sources, and where they disagree.
Nearby counties
| Place | Distance | Expansive clay | High water table |
|---|---|---|---|
| Watauga County, NC | 16 mi | 0% | 4% |
| Carter County, TN | 19 mi | 1% | 1% |
| Bristol city, VA | 20 mi | 0% | 5% |
| Ashe County, NC | 20 mi | 0% | 4% |
| Washington County, VA | 21 mi | 1% | 7% |
| Sullivan County, TN | 25 mi | 0% | 8% |
| Avery County, NC | 27 mi | 0% | 4% |
| Smyth County, VA | 32 mi | 11% | 5% |
Sources: USDA SSURGO (August 28, 2025) · US Drought Monitor (October 13, 2026) · FEMA NFIP v3 (September 9, 2026) · NOAA (August 2026) · Census ACS 2020-2024. Methods · Data status