Polk County, Missouri
A shallow water table limits basements on 59% of Polk County's mapped land, a higher share than 73% of US counties. Shrink-swell clay limits houses without basements on 24%.
100% of the county is in drought on the October 13, 2026 Drought Monitor map. FEMA's flood data list 3 flood losses here since 2016. 40% of homes were built before 1980, against 50% nationally; the median home dates from 1987.
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 Polk County
| Expansive clay (limits slab homes) | 24.0% |
| High water table (limits basements) | 59.1% |
| Septic fields very limited | 91.4% |
| Clay swell (LEP, by area) | 5.0% |
| High-swell land (LEP 6%+) | 27.8% |
| Mapped soil | 411,296 acres |
| Soil series | Share here | Series nationally: high water table |
|---|---|---|
| Viraton | 11% | n/a |
| Goss | 11% | 0% |
| Ocie | 7% | n/a |
| Alsup | 6% | n/a |
| Pomme | 5% | n/a |
| Bona | 5% | n/a |
How we count · survey areas MO167 (2025-09-02)
What the numbers mean here
Clay swell averages a linear extensibility of 5.0% by land area here, and 28% of the land reaches USDA's high class (6% or more). Clay like that swells when wet and shrinks when dry, under 24% of the mapped land.
Clay shrinks as it dries: 100% of the county is in drought on the latest map, and 24% of Polk County's mapped land has shrink-swell clay.
On 59% of Polk 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: 43.44 in, 0.95 in below the 1991-2020 average year of 44.39 in.
USDA rates 91% 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 28 of the last 52 weeks; the most was 100% of its area, in 26 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 | 100% |
| D3 extreme or worse | 64.3% |
| D4 exceptional | 0% |
Flood losses since 2016
3 flood losses since 2016, $123,773 paid. The worst year was 2026, with 1.
| Year | Flood losses |
|---|---|
| 2016 | 0 |
| 2017 | 1 |
| 2018 | 0 |
| 2019 | 0 |
| 2020 | 0 |
| 2021 | 0 |
| 2022 | 0 |
| 2023 | 0 |
| 2024 | 1 |
| 2025 | 0 |
| 2026 to date | 1 |
Rain
| Average year, 1991-2020 | 44.39 in |
| 12 months to August 2026 | 43.44 in (-0.95) |
| 2025 | 39.08 in (-5.31) |
| Wettest year since 1895 | 1927: 62.98 in |
| Driest year since 1895 | 1980: 24.29 in |
| Days with 1 inch or more, normal at BOLIVAR 1 NE (0 mi away) | 13.3 |
Homes
| Housing units | 13,482 |
| Median year built | 1987 |
| Built before 1980 | 40% |
| Built 2000 or later | 31% |
| Owner-occupied | 72% |
| Median value, owner-occupied | $205,800 |
| Single-family detached | 75% |
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 |
|---|---|---|---|
| Dallas County, MO | 21 mi | 22% | 66% |
| Hickory County, MO | 23 mi | 51% | 26% |
| Greene County, MO | 25 mi | 9% | 49% |
| Cedar County, MO | 26 mi | 11% | 49% |
| Dade County, MO | 28 mi | 17% | 45% |
| St. Clair County, MO | 36 mi | 23% | 33% |
| Webster County, MO | 37 mi | 20% | 68% |
| Lawrence County, MO | 42 mi | 8% | 68% |
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