Carroll County, Iowa
A shallow water table limits basements on 41% of Carroll County's mapped land, a higher share than 59% of US counties. Shrink-swell clay limits houses without basements on 18%.
None of the county is in drought on the October 13, 2026 Drought Monitor map. FEMA's flood data list no flood losses here since 2016. 72% of homes were built before 1980, against 50% nationally; the median home dates from 1964.
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 Carroll County
| Expansive clay (limits slab homes) | 17.7% |
| High water table (limits basements) | 40.6% |
| Septic fields very limited | 80.6% |
| Clay swell (LEP, by area) | 4.2% |
| High-swell land (LEP 6%+) | 3.4% |
| Mapped soil | 364,900 acres |
How we count · survey areas IA027 (2025-09-08)
What the numbers mean here
Clay swell averages a linear extensibility of 4.2% by land area here, and 3% of the land reaches USDA's high class (6% or more). Clay like that swells when wet and shrinks when dry, under 18% of the mapped land.
On 41% of Carroll 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: 25.64 in, 8.34 in below the 1991-2020 average year of 33.98 in.
USDA rates 81% 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 10 of the last 52 weeks; the most was 93.2% of its area, in 2 weeks, most recently on the August 11, 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
FEMA's flood data list no flood losses in Carroll County since 2016.
Rain
| Average year, 1991-2020 | 33.98 in |
| 12 months to August 2026 | 25.64 in (-8.34) |
| 2025 | 35.15 in (+1.17) |
| Wettest year since 1895 | 2015: 50.24 in |
| Driest year since 1895 | 1955: 19.53 in |
| Days with 1 inch or more, normal at CARROLL (2 mi away) | 7.4 |
Homes
| Housing units | 9,560 |
| Median year built | 1964 |
| Built before 1980 | 72% |
| Built 2000 or later | 13% |
| Owner-occupied | 77% |
| Median value, owner-occupied | $176,000 |
| Single-family detached | 82% |
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 |
|---|---|---|---|
| Greene County, IA | 25 mi | 11% | 71% |
| Audubon County, IA | 25 mi | 30% | 29% |
| Calhoun County, IA | 27 mi | 13% | 91% |
| Crawford County, IA | 27 mi | 12% | 15% |
| Sac County, IA | 27 mi | 26% | 63% |
| Guthrie County, IA | 31 mi | 62% | 66% |
| Shelby County, IA | 34 mi | 21% | 21% |
| Ida County, IA | 41 mi | 23% | 27% |
Sources: USDA SSURGO (September 8, 2025) · US Drought Monitor (October 13, 2026) · FEMA NFIP v3 (September 9, 2026) · NOAA (August 2026) · Census ACS 2020-2024. Methods · Data status