Washington County, Oklahoma
A shallow water table limits basements on 55% of Washington County's mapped land, a higher share than 71% of US counties and the 3rd highest of 77 Oklahoma counties. Shrink-swell clay limits houses without basements on 52%.
100% of the county is in drought on the October 13, 2026 Drought Monitor map. FEMA's flood data list 38 flood losses here since 2016, 5% of them in buildings with basements. 65% of homes were built before 1980, against 50% nationally; the median home dates from 1971.
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 Washington County
| Expansive clay (limits slab homes) | 52.1% |
| High water table (limits basements) | 54.9% |
| Septic fields very limited | 95.4% |
| Clay swell (LEP, by area) | 5.5% |
| High-swell land (LEP 6%+) | 40.2% |
| Mapped soil | 271,661 acres |
| Soil series | Share here | Series nationally: high water table |
|---|---|---|
| Dennis | 17% | 100% |
| Verdigris | 12% | n/a |
| Bates | 9% | n/a |
| Coweta | 8% | n/a |
| Eram | 8% | n/a |
| Summit | 8% | n/a |
How we count · survey areas OK147 (2025-08-29)
What the numbers mean here
Clay swell averages a linear extensibility of 5.5% by land area here, and 40% of the land reaches USDA's high class (6% or more). Clay like that swells when wet and shrinks when dry, under 52% of the mapped land.
Clay shrinks as it dries: 100% of the county is in drought on the latest map, and 52% of Washington County's mapped land has shrink-swell clay.
On 55% of Washington 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: 35.81 in, 5.66 in below the 1991-2020 average year of 41.47 in.
USDA rates 95% 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 33 of the last 52 weeks; the most was 100% of its area, in 19 weeks, most recently on the October 13, 2026 map.
| Category, October 13, 2026 | Share of county |
|---|---|
| D0 abnormally dry or worse | 100% |
| D1 moderate drought or worse | 100% |
| D2 severe or worse | 52.9% |
| D3 extreme or worse | 0% |
| D4 exceptional | 0% |
Flood losses since 2016
38 flood losses since 2016, $2.0 million paid. The worst year was 2019, with 32. Foundations of the buildings, where recorded: 5% basements, 76% slabs, 14% crawl spaces, 5% elevated. Median water depth outside the building: 20 in.
| Year | Flood losses |
|---|---|
| 2016 | 0 |
| 2017 | 6 |
| 2018 | 0 |
| 2019 | 32 |
| 2020 | 0 |
| 2021 | 0 |
| 2022 | 0 |
| 2023 | 0 |
| 2024 | 0 |
| 2025 | 0 |
| 2026 to date | 0 |
Rain
| Average year, 1991-2020 | 41.47 in |
| 12 months to August 2026 | 35.81 in (-5.66) |
| 2025 | 49.86 in (+8.39) |
| Wettest year since 1895 | 2019: 57.66 in |
| Driest year since 1895 | 1963: 21.38 in |
| Days with 1 inch or more, normal at BARTLESVILLE F P FLD (8 mi away) | 12 |
Homes
| Housing units | 23,741 |
| Median year built | 1971 |
| Built before 1980 | 65% |
| Built 2000 or later | 17% |
| Owner-occupied | 72% |
| Median value, owner-occupied | $173,200 |
| Single-family detached | 80% |
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 |
|---|---|---|---|
| Nowata County, OK | 17 mi | 48% | 49% |
| Rogers County, OK | 28 mi | 38% | 42% |
| Osage County, OK | 28 mi | 41% | 40% |
| Montgomery County, KS | 35 mi | 62% | 58% |
| Chautauqua County, KS | 36 mi | 67% | 51% |
| Craig County, OK | 39 mi | 53% | 58% |
| Tulsa County, OK | 40 mi | 47% | 52% |
| Mayes County, OK | 46 mi | 31% | 44% |
Sources: USDA SSURGO (August 29, 2025) · US Drought Monitor (October 13, 2026) · FEMA NFIP v3 (September 9, 2026) · NOAA (August 2026) · Census ACS 2020-2024. Methods · Data status