Columbia County, Oregon
A shallow water table limits basements on 35% of Columbia County's mapped land, a higher share than 53% of US counties and the 4th highest of 35 Oregon counties. Shrink-swell clay limits houses without basements on 7%.
None of the county is in drought on the October 13, 2026 Drought Monitor map. FEMA's flood data list 11 flood losses here since 2016. 49% of homes were built before 1980, against 50% nationally; the median home dates from 1981.
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 Columbia County
| Expansive clay (limits slab homes) | 6.7% |
| High water table (limits basements) | 35.0% |
| Septic fields very limited | 98.1% |
| Clay swell (LEP, by area) | 2.9% |
| High-swell land (LEP 6%+) | 6.7% |
| Mapped soil | 416,537 acres |
| Soil series | Share here | Series nationally: high water table |
|---|---|---|
| Bacona | 14% | n/a |
| Goble | 11% | n/a |
| Braun | 9% | n/a |
| Scaponia | 9% | n/a |
| Vernonia | 7% | n/a |
| Mayger | 5% | n/a |
How we count · survey areas OR009 (2025-09-09)
What the numbers mean here
On 35% of Columbia 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: 50.14 in, 6.66 in below the 1991-2020 average year of 56.80 in.
USDA rates 98% 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 8 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 | 99.3% |
| D1 moderate drought or worse | 0% |
| D2 severe or worse | 0% |
| D3 extreme or worse | 0% |
| D4 exceptional | 0% |
Flood losses since 2016
11 flood losses since 2016, $203,997 paid. The worst year was 2019, with 5.
| Year | Flood losses |
|---|---|
| 2016 | 1 |
| 2017 | 3 |
| 2018 | 0 |
| 2019 | 5 |
| 2020 | 1 |
| 2021 | 0 |
| 2022 | 0 |
| 2023 | 0 |
| 2024 | 0 |
| 2025 | 1 |
| 2026 to date | 0 |
Rain
| Average year, 1991-2020 | 56.80 in |
| 12 months to August 2026 | 50.14 in (-6.66) |
| 2025 | 47.55 in (-9.25) |
| Wettest year since 1895 | 1996: 82.72 in |
| Driest year since 1895 | 1929: 34.52 in |
| Days with 1 inch or more, normal at VERNONIA #2 (7 mi away) | 8.1 |
Homes
| Housing units | 22,167 |
| Median year built | 1981 |
| Built before 1980 | 49% |
| Built 2000 or later | 22% |
| Owner-occupied | 76% |
| Median value, owner-occupied | $421,600 |
| Single-family detached | 74% |
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 |
|---|---|---|---|
| Cowlitz County, WA | 26 mi | 4% | 10% |
| Washington County, OR | 27 mi | 7% | 42% |
| Wahkiakum County, WA | 30 mi | 4% | 10% |
| Clatsop County, OR | 31 mi | 1% | 12% |
| Clark County, WA | 31 mi | 3% | 22% |
| Multnomah County, OR | 42 mi | 0% | 30% |
| Tillamook County, OR | 47 mi | 1% | 5% |
| Yamhill County, OR | 49 mi | 31% | 36% |
Sources: USDA SSURGO (September 9, 2025) · US Drought Monitor (October 13, 2026) · FEMA NFIP v3 (September 9, 2026) · NOAA (August 2026) · Census ACS 2020-2024. Methods · Data status