Williamson County, Texas
Shrink-swell clay limits houses without basements on 60% of Williamson County's mapped land, a higher share than 94% of US counties. A shallow water table limits basements on 1%.
100% of the county is in drought on the November 3, 2026 Drought Monitor map. FEMA's flood data list 80 flood losses here since 2016, 0% of them in buildings with basements. 9% of homes were built before 1980, against 50% nationally; the median home dates from 2006.
Data as of November 3, 2026 · sources
expansive clay: shrink-swell limits slab homes
high water table: limits basements
in drought, November 3, 2026
of homes built before 1980
Soil under Williamson County
| Expansive clay (limits slab homes) | 60.1% |
| High water table (limits basements) | 1.3% |
| Septic fields very limited | 83.5% |
| Clay swell (LEP, by area) | 7.9% |
| High-swell land (LEP 6%+) | 60.3% |
| Mapped soil | 727,520 acres |
| Soil series | Share here | Series nationally: expansive clay |
|---|---|---|
| Eckrant | 15% | 8% |
| Branyon | 11% | 92% |
| Houston Black | 7% | 91% |
| Heiden | 6% | 80% |
| Georgetown | 5% | n/a |
| Austin | 5% | 93% |
How we count · survey areas TX491 (2025-09-05)
What the numbers mean here
Clay swell averages a linear extensibility of 7.9% by land area here, and 60% of the land reaches USDA's high class (6% or more). Clay like that swells when wet and shrinks when dry, under 60% of the mapped land.
Clay shrinks as it dries: 100% of the county is in drought on the latest map, and 60% of Williamson County's mapped land has shrink-swell clay.
Rain over the 12 months to August 2026: 31.96 in, 3.96 in below the 1991-2020 average year of 35.92 in.
USDA rates 84% of the land very limited for septic absorption fields.
Drought
100% of the county is in drought (D1 or worse) on the November 3, 2026 map. Part of the county was in drought in 48 of the last 52 weeks; the most was 100% of its area, in 12 weeks, most recently on the November 3, 2026 map.
| Category, November 3, 2026 | Share of county |
|---|---|
| D0 abnormally dry or worse | 100% |
| D1 moderate drought or worse | 100% |
| D2 severe or worse | 77.6% |
| D3 extreme or worse | 0% |
| D4 exceptional | 0% |
Flood losses since 2016
80 flood losses since 2016, $4.0 million paid. The worst year was 2025, with 43. Foundations of the buildings, where recorded: 77% slabs, 5% crawl spaces, 18% elevated. Median water depth outside the building: 28 in.
| Year | Flood losses |
|---|---|
| 2016 | 11 |
| 2017 | 2 |
| 2018 | 8 |
| 2019 | 3 |
| 2020 | 2 |
| 2021 | 1 |
| 2022 | 1 |
| 2023 | 4 |
| 2024 | 0 |
| 2025 | 43 |
| 2026 to date | 5 |
Rain
| Average year, 1991-2020 | 35.92 in |
| 12 months to August 2026 | 31.96 in (-3.96) |
| 2025 | 33.18 in (-2.74) |
| Wettest year since 1895 | 1919: 55.27 in |
| Driest year since 1895 | 1954: 12.67 in |
| Days with 1 inch or more, normal at GEORGETOWN LAKE (7 mi away) | 11.6 |
Homes
| Housing units | 262,644 |
| Median year built | 2006 |
| Built before 1980 | 9% |
| Built 2000 or later | 64% |
| Owner-occupied | 66% |
| Median value, owner-occupied | $447,000 |
| Single-family detached | 73% |
What repairs cost
Published ranges from cost guides, not quotes. More sources, and where they disagree.
Cities in Williamson County
| City | Expansive clay | High water table | Homes |
|---|---|---|---|
| Bartlett | 84% | 0% | 669 |
| Cedar Park | 48% | 0% | 29,364 |
| Coupland | 81% | 1% | 180 |
| Florence | 74% | under 1% | 349 |
| Georgetown | 42% | under 1% | 37,206 |
| Granger | 85% | under 1% | 485 |
| Hutto | 70% | under 1% | 12,151 |
| Jarrell | 49% | 0% | 1,222 |
| Leander | 48% | under 1% | 27,000 |
| Liberty Hill | 56% | 0% | 2,719 |
| Round Rock | 56% | under 1% | 51,143 |
| Taylor | 81% | under 1% | 7,016 |
| Thrall | 84% | under 1% | 289 |
| Weir | 57% | under 1% | 154 |
Nearby counties
| Place | Distance | Expansive clay | High water table |
|---|---|---|---|
| Bell County, TX | 28 mi | 55% | 1% |
| Travis County, TX | 29 mi | 39% | under 1% |
| Burnet County, TX | 37 mi | 27% | 0% |
| Milam County, TX | 38 mi | 61% | 12% |
| Bastrop County, TX | 42 mi | 52% | 14% |
| Lee County, TX | 44 mi | 48% | 25% |
| Hays County, TX | 48 mi | 14% | under 1% |
| Coryell County, TX | 53 mi | 26% | under 1% |
Sources: USDA SSURGO (September 5, 2025) · US Drought Monitor (November 3, 2026) · FEMA NFIP v3 (September 9, 2026) · NOAA (August 2026) · Census ACS 2020-2024. Methods · Data status