Knox County, Tennessee
USDA's soil survey flags shrink-swell clay on 0% of Knox County's mapped land and a shallow water table under basements on 8%, 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 115 flood losses here since 2016, 18% of them in buildings with basements. 43% of homes were built before 1980, against 50% nationally; the median home dates from 1985.
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 Knox County
| Expansive clay (limits slab homes) | 0.0% |
| High water table (limits basements) | 8.5% |
| Septic fields very limited | 57.4% |
| Clay swell (LEP, by area) | 3.5% |
| High-swell land (LEP 6%+) | 0.0% |
| Urban land, not rated | 6.2% |
| Mapped soil | 336,600 acres |
How we count · survey areas TN093 (2025-08-28)
What the numbers mean here
Rain over the 12 months to August 2026: 49.21 in, 4.51 in below the 1991-2020 average year of 53.72 in.
USDA rates 57% of the land very limited for septic absorption fields.
With shrink-swell clay on 0% and a shallow water table on 8% of the land, the soil survey points to neither problem across most of Knox 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 25 of the last 52 weeks; the most was 100% of its area, in 7 weeks, most recently on the May 26, 2026 map.
| Category, October 13, 2026 | Share of county |
|---|---|
| D0 abnormally dry or worse | 18.8% |
| D1 moderate drought or worse | 0% |
| D2 severe or worse | 0% |
| D3 extreme or worse | 0% |
| D4 exceptional | 0% |
Flood losses since 2016
115 flood losses since 2016, $2.4 million paid. The worst year was 2019, with 54. Foundations of the buildings, where recorded: 18% basements, 23% slabs, 32% crawl spaces, 27% elevated. Median water depth outside the building: 11 in.
| Year | Flood losses |
|---|---|
| 2016 | 2 |
| 2017 | 3 |
| 2018 | 3 |
| 2019 | 54 |
| 2020 | 27 |
| 2021 | 10 |
| 2022 | 9 |
| 2023 | 1 |
| 2024 | 5 |
| 2025 | 0 |
| 2026 to date | 1 |
Rain
| Average year, 1991-2020 | 53.72 in |
| 12 months to August 2026 | 49.21 in (-4.51) |
| 2025 | 48.54 in (-5.18) |
| Wettest year since 1895 | 2020: 68.03 in |
| Driest year since 1895 | 2007: 33.27 in |
| Days with 1 inch or more, normal at KNOXVILLE EXP STN (7 mi away) | 15.9 |
Homes
| Housing units | 218,661 |
| Median year built | 1985 |
| Built before 1980 | 43% |
| Built 2000 or later | 29% |
| Owner-occupied | 65% |
| Median value, owner-occupied | $320,900 |
| Single-family detached | 66% |
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 |
|---|---|---|---|
| Anderson County, TN | 17 mi | 2% | 7% |
| Union County, TN | 21 mi | under 1% | 5% |
| Blount County, TN | 21 mi | under 1% | 5% |
| Sevier County, TN | 27 mi | 0% | 7% |
| Loudon County, TN | 28 mi | under 1% | 4% |
| Jefferson County, TN | 28 mi | 0% | 5% |
| Campbell County, TN | 31 mi | 0% | 2% |
| Grainger County, TN | 31 mi | 2% | 3% |
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