Arapahoe County, Colorado
Shrink-swell clay limits houses without basements on 22% of Arapahoe County's mapped land, a higher share than 72% of US counties and the 8th highest of 63 Colorado counties. A shallow water table limits basements on 1%.
36.9% of the county is in drought on the October 13, 2026 Drought Monitor map. FEMA's flood data list 59 flood losses here since 2016, 83% of them in buildings with basements. 38% of homes were built before 1980, against 50% nationally; the median home dates from 1986.
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 Arapahoe County
| Expansive clay (limits slab homes) | 21.5% |
| High water table (limits basements) | 0.7% |
| Septic fields very limited | 51.5% |
| Clay swell (LEP, by area) | 4.4% |
| High-swell land (LEP 6%+) | 35.4% |
| Mapped soil | 524,410 acres |
| Soil series | Share here | Series nationally: expansive clay |
|---|---|---|
| Bresser | 9% | n/a |
| Nunn | 8% | n/a |
| Renohill | 7% | n/a |
| Weld | 6% | n/a |
| Fondis | 6% | n/a |
| Truckton | 6% | n/a |
How we count · survey areas CO005 (2025-08-29), CO031 (2025-08-29)
What the numbers mean here
Clay swell averages a linear extensibility of 4.4% by land area here, and 35% of the land reaches USDA's high class (6% or more). Clay like that swells when wet and shrinks when dry, under 22% of the mapped land.
Clay shrinks as it dries: 36.9% of the county is in drought on the latest map, and 22% of Arapahoe County's mapped land has shrink-swell clay.
Rain over the 12 months to August 2026: 12.49 in, 3.86 in below the 1991-2020 average year of 16.35 in.
USDA rates 52% of the land very limited for septic absorption fields.
Drought
36.9% 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 8 weeks, most recently on the May 19, 2026 map.
| Category, October 13, 2026 | Share of county |
|---|---|
| D0 abnormally dry or worse | 53.1% |
| D1 moderate drought or worse | 36.9% |
| D2 severe or worse | 24.9% |
| D3 extreme or worse | 0% |
| D4 exceptional | 0% |
Flood losses since 2016
59 flood losses since 2016, $197,311 paid. The worst year was 2023, with 31. Foundations of the buildings, where recorded: 83% basements, 6% slabs, 4% crawl spaces, 6% elevated.
| Year | Flood losses |
|---|---|
| 2016 | 3 |
| 2017 | 1 |
| 2018 | 3 |
| 2019 | 3 |
| 2020 | 1 |
| 2021 | 9 |
| 2022 | 1 |
| 2023 | 31 |
| 2024 | 3 |
| 2025 | 1 |
| 2026 to date | 3 |
Rain
| Average year, 1991-2020 | 16.35 in |
| 12 months to August 2026 | 12.49 in (-3.86) |
| 2025 | 15.24 in (-1.11) |
| Wettest year since 1895 | 2023: 24.20 in |
| Driest year since 1895 | 1954: 7.32 in |
| Days with 1 inch or more, normal at BYERS 5 ENE (13 mi away) | 2.5 |
Homes
| Housing units | 269,345 |
| Median year built | 1986 |
| Built before 1980 | 38% |
| Built 2000 or later | 28% |
| Owner-occupied | 65% |
| Median value, owner-occupied | $561,200 |
| Single-family detached | 56% |
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 |
|---|---|---|---|
| Adams County, CO | 16 mi | 11% | 2% |
| Elbert County, CO | 26 mi | 11% | 2% |
| Denver County, CO | 30 mi | 15% | 3% |
| Douglas County, CO | 39 mi | 3% | 2% |
| Broomfield County, CO | 44 mi | 46% | 1% |
| Jefferson County, CO | 49 mi | 17% | 2% |
| Morgan County, CO | 51 mi | 10% | 3% |
| El Paso County, CO | 57 mi | 6% | 1% |
Sources: USDA SSURGO (August 29, 2025) · US Drought Monitor (October 13, 2026) · FEMA NFIP v3 (September 9, 2026) · NOAA (August 2026) · Census ACS 2020-2024. Methods · Data status