Clackamas County, Oregon
A shallow water table limits basements on 30% of Clackamas County's mapped land and the 6th highest of 35 Oregon counties. Shrink-swell clay limits houses without basements on 5%.
The soil survey maps 55% of the county's land area; these shares describe the mapped part. 94.6% of the county is in drought on the October 13, 2026 Drought Monitor map. FEMA's flood data list 78 flood losses here since 2016, 14% of them in buildings with basements. 44% of homes were built before 1980, against 50% nationally; the median home dates from 1985.
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 Clackamas County
| Expansive clay (limits slab homes) | 5.4% |
| High water table (limits basements) | 30.3% |
| Septic fields very limited | 94.5% |
| Clay swell (LEP, by area) | 3.1% |
| High-swell land (LEP 6%+) | 5.4% |
| Mapped soil | 659,753 acres |
| Soil series | Share here | Series nationally: high water table |
|---|---|---|
| Jory | 8% | n/a |
| Alspaugh | 6% | n/a |
| Aloha | 4% | n/a |
| Aschoff | 4% | n/a |
| Highcamp | 4% | n/a |
| Klickitat | 4% | n/a |
How we count · survey areas OR610 (2025-09-09), OR674 (2025-09-10)
What the numbers mean here
On 30% of Clackamas 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: 65.51 in, 9.40 in below the 1991-2020 average year of 74.91 in.
USDA rates 94% of the land very limited for septic absorption fields.
Drought
94.6% of the county is in drought (D1 or worse) on the October 13, 2026 map. Part of the county was in drought in 39 of the last 52 weeks; the most was 100% of its area, in 7 weeks, most recently on the December 2, 2025 map.
| Category, October 13, 2026 | Share of county |
|---|---|
| D0 abnormally dry or worse | 100% |
| D1 moderate drought or worse | 94.6% |
| D2 severe or worse | 12.9% |
| D3 extreme or worse | 0% |
| D4 exceptional | 0% |
Flood losses since 2016
78 flood losses since 2016, $3.3 million paid. The worst year was 2025, with 54. Foundations of the buildings, where recorded: 14% basements, 13% slabs, 47% crawl spaces, 26% elevated. Median water depth outside the building: 16 in.
| Year | Flood losses |
|---|---|
| 2016 | 3 |
| 2017 | 4 |
| 2018 | 0 |
| 2019 | 0 |
| 2020 | 1 |
| 2021 | 9 |
| 2022 | 4 |
| 2023 | 0 |
| 2024 | 0 |
| 2025 | 54 |
| 2026 to date | 3 |
Rain
| Average year, 1991-2020 | 74.91 in |
| 12 months to August 2026 | 65.51 in (-9.40) |
| 2025 | 67.27 in (-7.64) |
| Wettest year since 1895 | 1996: 117.92 in |
| Driest year since 1895 | 1944: 47.12 in |
| Days with 1 inch or more, normal at THREE LYNX (7 mi away) | 15.6 |
Homes
| Housing units | 174,323 |
| Median year built | 1985 |
| Built before 1980 | 44% |
| Built 2000 or later | 26% |
| Owner-occupied | 71% |
| Median value, owner-occupied | $611,000 |
| Single-family detached | 68% |
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 |
|---|---|---|---|
| Marion County, OR | 26 mi | 19% | 40% |
| Multnomah County, OR | 29 mi | 0% | 30% |
| Hood River County, OR | 36 mi | 0% | 5% |
| Clark County, WA | 44 mi | 3% | 22% |
| Linn County, OR | 49 mi | 25% | 34% |
| Wasco County, OR | 50 mi | 15% | 2% |
| Washington County, OR | 52 mi | 7% | 42% |
| Yamhill County, OR | 55 mi | 31% | 36% |
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