Marion County, Oregon
A shallow water table limits basements on 40% of Marion County's mapped land, a higher share than 58% of US counties and the 2nd highest of 35 Oregon counties. Shrink-swell clay limits houses without basements on 19%.
The soil survey maps 73% of the county's land area; these shares describe the mapped part. 99.4% of the county is in drought on the October 13, 2026 Drought Monitor map. FEMA's flood data list 25 flood losses here since 2016. 51% of homes were built before 1980, against 50% nationally; the median home dates from 1979.
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 Marion County
| Expansive clay (limits slab homes) | 18.5% |
| High water table (limits basements) | 40.3% |
| Septic fields very limited | 92.6% |
| Clay swell (LEP, by area) | 4.4% |
| High-swell land (LEP 6%+) | 21.6% |
| Mapped soil | 550,142 acres |
| Soil series | Share here | Series nationally: high water table |
|---|---|---|
| Woodburn | 13% | n/a |
| Nekia | 13% | n/a |
| McCully | 10% | n/a |
| Amity | 8% | n/a |
| Kinney | 7% | n/a |
| Jory | 4% | n/a |
How we count · survey areas OR643 (2025-09-10), OR674 (2025-09-10)
What the numbers mean here
Clay swell averages a linear extensibility of 4.4% by land area here, and 22% of the land reaches USDA's high class (6% or more). Clay like that swells when wet and shrinks when dry, under 19% of the mapped land.
Clay shrinks as it dries: 99.4% of the county is in drought on the latest map, and 19% of Marion County's mapped land has shrink-swell clay.
On 40% of Marion 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: 54.71 in, 10.11 in below the 1991-2020 average year of 64.82 in.
USDA rates 93% of the land very limited for septic absorption fields.
Drought
99.4% of the county is in drought (D1 or worse) on the October 13, 2026 map. Part of the county was in drought in 40 of the last 52 weeks; the most was 100% of its area, in 8 weeks, most recently on the December 9, 2025 map.
| Category, October 13, 2026 | Share of county |
|---|---|
| D0 abnormally dry or worse | 100% |
| D1 moderate drought or worse | 99.4% |
| D2 severe or worse | 36.7% |
| D3 extreme or worse | 0% |
| D4 exceptional | 0% |
Flood losses since 2016
25 flood losses since 2016, $284,943 paid. The worst year was 2025, with 7.
| Year | Flood losses |
|---|---|
| 2016 | 3 |
| 2017 | 4 |
| 2018 | 1 |
| 2019 | 3 |
| 2020 | 2 |
| 2021 | 4 |
| 2022 | 0 |
| 2023 | 0 |
| 2024 | 1 |
| 2025 | 7 |
| 2026 to date | 0 |
Rain
| Average year, 1991-2020 | 64.82 in |
| 12 months to August 2026 | 54.71 in (-10.11) |
| 2025 | 57.08 in (-7.74) |
| Wettest year since 1895 | 1996: 102.94 in |
| Driest year since 1895 | 1944: 41.96 in |
| Days with 1 inch or more, normal at SILVERTON (12 mi away) | 6.3 |
Homes
| Housing units | 132,295 |
| Median year built | 1979 |
| Built before 1980 | 51% |
| Built 2000 or later | 23% |
| Owner-occupied | 62% |
| Median value, owner-occupied | $416,400 |
| Single-family detached | 63% |
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 |
|---|---|---|---|
| Clackamas County, OR | 26 mi | 5% | 30% |
| Linn County, OR | 29 mi | 25% | 34% |
| Polk County, OR | 40 mi | 18% | 30% |
| Yamhill County, OR | 43 mi | 31% | 36% |
| Multnomah County, OR | 45 mi | 0% | 30% |
| Benton County, OR | 49 mi | 22% | 24% |
| Washington County, OR | 52 mi | 7% | 42% |
| Clark County, WA | 60 mi | 3% | 22% |
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