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Cowlitz County, Washington
USDA's soil survey flags shrink-swell clay on 4% of Cowlitz County's mapped land and a shallow water table under basements on 10%, both below the national shares of 15% and 29%. None of the county is in drought on the October 13, 2026 Drought Monitor map.
FEMA's flood data list 34 flood losses here since 2016, 15% of them in buildings with basements. 57% of homes were built before 1980, against 50% nationally; the median home dates from 1976.
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 Cowlitz County
| Expansive clay (limits slab homes) | 4.0% |
| High water table (limits basements) | 10.3% |
| Septic fields very limited | 72.2% |
| Clay swell (LEP, by area) | 3.1% |
| High-swell land (LEP 6%+) | 4.3% |
| Mapped soil | 738,071 acres |
| Soil series | Share here | Series nationally: expansive clay |
|---|---|---|
| Hazeldell | 11% | n/a |
| Olympic | 9% | n/a |
| Pheeney | 4% | n/a |
| Vanson | 4% | n/a |
| Cinebar | 4% | n/a |
| Germany | 3% | n/a |
How we count · survey areas WA015 (2025-08-28)
What the numbers mean here
Rain over the 12 months to August 2026: 75.81 in, 2.62 in below the 1991-2020 average year of 78.43 in.
USDA rates 72% of the land very limited for septic absorption fields.
With shrink-swell clay on 4% and a shallow water table on 10% of the land, the soil survey points to neither problem across most of Cowlitz County; conditions still vary lot by lot.
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 7 weeks, most recently on the December 2, 2025 map.
| Category, October 13, 2026 | Share of county |
|---|---|
| D0 abnormally dry or worse | 96% |
| D1 moderate drought or worse | 0% |
| D2 severe or worse | 0% |
| D3 extreme or worse | 0% |
| D4 exceptional | 0% |
Flood losses since 2016
34 flood losses since 2016, $1.1 million paid. The worst year was 2022, with 9. Foundations of the buildings, where recorded: 15% basements, 15% slabs, 46% crawl spaces, 23% elevated.
| Year | Flood losses |
|---|---|
| 2016 | 1 |
| 2017 | 6 |
| 2018 | 1 |
| 2019 | 3 |
| 2020 | 1 |
| 2021 | 1 |
| 2022 | 9 |
| 2023 | 0 |
| 2024 | 0 |
| 2025 | 8 |
| 2026 to date | 4 |
Rain
| Average year, 1991-2020 | 78.43 in |
| 12 months to August 2026 | 75.81 in (-2.62) |
| 2025 | 73.07 in (-5.36) |
| Wettest year since 1895 | 1996: 110.40 in |
| Driest year since 1895 | 1944: 49.83 in |
| Days with 1 inch or more, normal at LONGVIEW (12 mi away) | 5.5 |
Homes
| Housing units | 46,422 |
| Median year built | 1976 |
| Built before 1980 | 57% |
| Built 2000 or later | 21% |
| Owner-occupied | 68% |
| Median value, owner-occupied | $397,500 |
| Single-family detached | 69% |
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 |
|---|---|---|---|
| Columbia County, OR | 26 mi | 7% | 35% |
| Lewis County, WA | 30 mi | 7% | 20% |
| Clark County, WA | 31 mi | 3% | 22% |
| Wahkiakum County, WA | 36 mi | 4% | 10% |
| Skamania County, WA | 37 mi | 4% | 5% |
| Multnomah County, OR | 47 mi | 0% | 30% |
| Washington County, OR | 49 mi | 7% | 42% |
| Clatsop County, OR | 51 mi | 1% | 12% |
Sources: USDA SSURGO (August 28, 2025) · US Drought Monitor (October 13, 2026) · FEMA NFIP v3 (September 9, 2026) · NOAA (August 2026) · Census ACS 2020-2024. Methods · Data status