Decatur County, Iowa
A shallow water table limits basements on 76% of Decatur County's mapped land, a higher share than 86% of US counties. Shrink-swell clay limits houses without basements on 66%.
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. 63% of homes were built before 1980, against 50% nationally; the median home dates from 1970.
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 Decatur County
| Expansive clay (limits slab homes) | 66.4% |
| High water table (limits basements) | 76.3% |
| Septic fields very limited | 95.0% |
| Clay swell (LEP, by area) | 6.4% |
| High-swell land (LEP 6%+) | 55.4% |
| Mapped soil | 342,600 acres |
How we count · survey areas IA053 (2025-09-08)
What the numbers mean here
Clay swell averages a linear extensibility of 6.4% by land area here, and 55% of the land reaches USDA's high class (6% or more). Clay like that swells when wet and shrinks when dry, under 66% of the mapped land.
On 76% of Decatur 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: 37.09 in, 0.79 in below the 1991-2020 average year of 37.88 in.
USDA rates 95% 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 100% of its area, on the March 3, 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 Decatur County since 2016.
Rain
| Average year, 1991-2020 | 37.88 in |
| 12 months to August 2026 | 37.09 in (-0.79) |
| 2025 | 32.70 in (-5.18) |
| Wettest year since 1895 | 1993: 53.82 in |
| Driest year since 1895 | 1988: 17.66 in |
| Days with 1 inch or more, normal at LAMONI (11 mi away) | 10.3 |
Homes
| Housing units | 3,659 |
| Median year built | 1970 |
| Built before 1980 | 63% |
| Built 2000 or later | 16% |
| Owner-occupied | 70% |
| Median value, owner-occupied | $113,900 |
| Single-family detached | 77% |
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 |
|---|---|---|---|
| Clarke County, IA | 20 mi | 74% | 78% |
| Wayne County, IA | 24 mi | 77% | 80% |
| Ringgold County, IA | 24 mi | 76% | 77% |
| Mercer County, MO | 25 mi | 79% | 62% |
| Harrison County, MO | 29 mi | 66% | 68% |
| Lucas County, IA | 31 mi | 73% | 78% |
| Union County, IA | 31 mi | 85% | 78% |
| Worth County, MO | 38 mi | 41% | 58% |
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