Henderson County, Illinois
A shallow water table limits basements on 43% of Henderson County's mapped land, a higher share than 60% of US counties. Shrink-swell clay limits houses without basements on 13%.
None of the county is in drought on the October 13, 2026 Drought Monitor map. FEMA's flood data list 46 flood losses here since 2016, 11% of them in buildings with basements. 67% of homes were built before 1980, against 50% nationally; the median home dates from 1972.
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 Henderson County
| Expansive clay (limits slab homes) | 13.4% |
| High water table (limits basements) | 42.6% |
| Septic fields very limited | 60.4% |
| Clay swell (LEP, by area) | 4.0% |
| High-swell land (LEP 6%+) | 5.9% |
| Mapped soil | 253,310 acres |
| Soil series | Share here | Series nationally: high water table |
|---|---|---|
| Muscatune | 14% | n/a |
| Seaton | 13% | n/a |
| Osco | 8% | 3% |
| Coloma | 6% | n/a |
| Hickory | 5% | n/a |
| Rozetta | 5% | n/a |
How we count · survey areas IL071 (2025-08-31)
What the numbers mean here
On 43% of Henderson 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: 37.11 in, 0.78 in below the 1991-2020 average year of 37.89 in.
USDA rates 60% 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 20 of the last 52 weeks; the most was 100% of its area, in 17 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
46 flood losses since 2016, $856,814 paid. The worst year was 2019, with 24. Foundations of the buildings, where recorded: 11% basements, 11% slabs, 78% elevated. Median water depth outside the building: 49 in.
| Year | Flood losses |
|---|---|
| 2016 | 3 |
| 2017 | 4 |
| 2018 | 6 |
| 2019 | 24 |
| 2020 | 0 |
| 2021 | 0 |
| 2022 | 0 |
| 2023 | 4 |
| 2024 | 4 |
| 2025 | 0 |
| 2026 to date | 1 |
Rain
| Average year, 1991-2020 | 37.89 in |
| 12 months to August 2026 | 37.11 in (-0.78) |
| 2025 | 29.71 in (-8.18) |
| Wettest year since 1895 | 2009: 52.64 in |
| Driest year since 1895 | 1901: 21.95 in |
| Days with 1 inch or more, normal at GLADSTONE DAM 18 (6 mi away) | 9.5 |
Homes
| Housing units | 3,366 |
| Median year built | 1972 |
| Built before 1980 | 67% |
| Built 2000 or later | 11% |
| Owner-occupied | 81% |
| Median value, owner-occupied | $104,400 |
| 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 |
|---|---|---|---|
| Des Moines County, IA | 15 mi | 57% | 80% |
| Warren County, IL | 17 mi | 35% | 54% |
| McDonough County, IL | 28 mi | 63% | 70% |
| Mercer County, IL | 29 mi | 15% | 44% |
| Lee County, IA | 30 mi | 61% | 77% |
| Hancock County, IL | 31 mi | 48% | 72% |
| Louisa County, IA | 32 mi | 38% | 70% |
| Henry County, IA | 34 mi | 76% | 86% |
Sources: USDA SSURGO (August 31, 2025) · US Drought Monitor (October 13, 2026) · FEMA NFIP v3 (September 9, 2026) · NOAA (August 2026) · Census ACS 2020-2024. Methods · Data status