Union County, Iowa
Shrink-swell clay limits houses without basements on 85% of Union County's mapped land, a higher share than 100% of US counties and the 5th highest of 99 Iowa counties. A shallow water table limits basements on 78%.
None of the county is in drought on the October 13, 2026 Drought Monitor map. FEMA's flood data list 1 flood losses here since 2016. 73% of homes were built before 1980, against 50% nationally; the median home dates from 1962.
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 Union County
| Expansive clay (limits slab homes) | 84.7% |
| High water table (limits basements) | 78.4% |
| Septic fields very limited | 97.7% |
| Clay swell (LEP, by area) | 6.5% |
| High-swell land (LEP 6%+) | 51.2% |
| Mapped soil | 273,100 acres |
| Soil series | Share here | Series nationally: expansive clay |
|---|---|---|
| Sharpsburg | 15% | 98% |
| Shelby | 10% | n/a |
| Colo | 9% | n/a |
| Gara | 7% | 65% |
| Clarinda | 6% | n/a |
| Nira | 6% | n/a |
How we count · survey areas IA175 (2025-09-09)
What the numbers mean here
Clay swell averages a linear extensibility of 6.5% by land area here, and 51% of the land reaches USDA's high class (6% or more). Clay like that swells when wet and shrinks when dry, under 85% of the mapped land.
On 78% of Union 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: 36.88 in, 0.30 in above the 1991-2020 average year of 36.58 in.
USDA rates 98% of the land very limited for septic absorption fields.
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 5 of the last 52 weeks; the most was 13.4% of its area, in 5 weeks, most recently on the March 31, 2026 map.
| Category, October 13, 2026 | Share of county |
|---|---|
| D0 abnormally dry or worse | 0% |
| D1 moderate drought or worse | 0% |
| D2 severe or worse | 0% |
| D3 extreme or worse | 0% |
| D4 exceptional | 0% |
Flood losses since 2016
1 flood losses since 2016, $7,107 paid. The worst year was 2026, with 1.
| Year | Flood losses |
|---|---|
| 2016 | 0 |
| 2017 | 0 |
| 2018 | 0 |
| 2019 | 0 |
| 2020 | 0 |
| 2021 | 0 |
| 2022 | 0 |
| 2023 | 0 |
| 2024 | 0 |
| 2025 | 0 |
| 2026 to date | 1 |
Rain
| Average year, 1991-2020 | 36.58 in |
| 12 months to August 2026 | 36.88 in (+0.30) |
| 2025 | 32.90 in (-3.68) |
| Wettest year since 1895 | 1973: 53.90 in |
| Driest year since 1895 | 1988: 17.35 in |
| Days with 1 inch or more, normal at BEACONSFIELD (18 mi away) | 10.2 |
Homes
| Housing units | 5,785 |
| Median year built | 1962 |
| Built before 1980 | 73% |
| Built 2000 or later | 13% |
| Owner-occupied | 72% |
| Median value, owner-occupied | $122,000 |
| 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 |
|---|---|---|---|
| Ringgold County, IA | 20 mi | 76% | 77% |
| Adams County, IA | 24 mi | 88% | 78% |
| Clarke County, IA | 24 mi | 74% | 78% |
| Adair County, IA | 24 mi | 91% | 80% |
| Madison County, IA | 24 mi | 88% | 77% |
| Taylor County, IA | 31 mi | 85% | 83% |
| Decatur County, IA | 31 mi | 66% | 76% |
| Worth County, MO | 39 mi | 41% | 58% |
Sources: USDA SSURGO (September 9, 2025) · US Drought Monitor (October 13, 2026) · FEMA NFIP v3 (September 9, 2026) · NOAA (August 2026) · Census ACS 2020-2024. Methods · Data status