Rock County, Minnesota
A shallow water table limits basements on 54% of Rock County's mapped land, a higher share than 70% of US counties. Shrink-swell clay limits houses without basements on 24%.
64.2% of the county is in drought on the October 13, 2026 Drought Monitor map. FEMA's flood data list 4 flood losses here since 2016. 76% of homes were built before 1980, against 50% nationally; the median home dates from 1960.
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 Rock County
| Expansive clay (limits slab homes) | 24.5% |
| High water table (limits basements) | 53.8% |
| Septic fields very limited | 92.0% |
| Clay swell (LEP, by area) | 4.5% |
| High-swell land (LEP 6%+) | 1.8% |
| Mapped soil | 309,100 acres |
| Soil series | Share here | Series nationally: high water table |
|---|---|---|
| Moody | 12% | 0% |
| Trent | 11% | n/a |
| Splitrock | 10% | n/a |
| Whitewood | 8% | n/a |
| Marcus | 5% | n/a |
| Spillco | 5% | n/a |
How we count · survey areas MN133 (2025-09-10)
What the numbers mean here
Clay swell averages a linear extensibility of 4.5% by land area here, and 2% 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: 64.2% of the county is in drought on the latest map, and 24% of Rock County's mapped land has shrink-swell clay.
On 54% of Rock 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: 17.41 in, 10.89 in below the 1991-2020 average year of 28.30 in.
USDA rates 92% of the land very limited for septic absorption fields.
Drought
64.2% of the county is in drought (D1 or worse) on the October 13, 2026 map. Part of the county was in drought in 52 of the last 52 weeks; the most was 100% of its area, in 16 weeks, most recently on the September 8, 2026 map.
| Category, October 13, 2026 | Share of county |
|---|---|
| D0 abnormally dry or worse | 85% |
| D1 moderate drought or worse | 64.2% |
| D2 severe or worse | 0% |
| D3 extreme or worse | 0% |
| D4 exceptional | 0% |
Flood losses since 2016
4 flood losses since 2016, $19,090 paid. The worst year was 2018, with 2.
| Year | Flood losses |
|---|---|
| 2016 | 0 |
| 2017 | 0 |
| 2018 | 2 |
| 2019 | 1 |
| 2020 | 0 |
| 2021 | 0 |
| 2022 | 1 |
| 2023 | 0 |
| 2024 | 0 |
| 2025 | 0 |
| 2026 to date | 0 |
Rain
| Average year, 1991-2020 | 28.30 in |
| 12 months to August 2026 | 17.41 in (-10.89) |
| 2025 | 22.67 in (-5.63) |
| Wettest year since 1895 | 2018: 40.01 in |
| Driest year since 1895 | 1976: 12.56 in |
| Days with 1 inch or more, normal at ROCK RAPIDS (17 mi away) | 6.4 |
Homes
| Housing units | 4,256 |
| Median year built | 1960 |
| Built before 1980 | 76% |
| Built 2000 or later | 12% |
| Owner-occupied | 77% |
| Median value, owner-occupied | $224,300 |
| Single-family detached | 79% |
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 |
|---|---|---|---|
| Lyon County, IA | 20 mi | 18% | 37% |
| Pipestone County, MN | 24 mi | 8% | 75% |
| Nobles County, MN | 25 mi | 10% | 90% |
| Minnehaha County, SD | 27 mi | 17% | 32% |
| Moody County, SD | 31 mi | 10% | 36% |
| Murray County, MN | 35 mi | 10% | 85% |
| Lincoln County, SD | 35 mi | 28% | 51% |
| Osceola County, IA | 37 mi | 21% | 76% |
Sources: USDA SSURGO (September 10, 2025) · US Drought Monitor (October 13, 2026) · FEMA NFIP v3 (September 9, 2026) · NOAA (August 2026) · Census ACS 2020-2024. Methods · Data status