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Washington soil by county

Across Washington's mapped land, shrink-swell clay limits houses without basements on 2% and a shallow water table limits basements on 14%.

Highest clay shares: Asotin County (29%), Garfield County (13%), Lewis County (7%), Grays Harbor County (6%), Kittitas County (5%). Highest water-table shares: Snohomish County (72%), Island County (65%), Kitsap County (65%), San Juan County (47%), Skagit County (46%).

Data as of September 22, 2026 · 39 counties

Adams County: 0%Asotin County: 29%Benton County: 0%Chelan County: 0%Clallam County: 1%Clark County: 3%Columbia County: 0%Cowlitz County: 4%Douglas County: 0%Ferry County: 0%Franklin County: 0%Garfield County: 13%Grant County: 0%Grays Harbor County: 6%Island County: 0%Jefferson County: 1%King County: 0%Kitsap County: 0%Kittitas County: 5%Klickitat County: 2%Lewis County: 7%Lincoln County: 1%Mason County: 0%Okanogan County: 0%Pacific County: 4%Pend Oreille County: 0%Pierce County: 2%San Juan County: 0%Skagit County: 0%Skamania County: 4%Snohomish County: 1%Spokane County: 3%Stevens County: 0%Thurston County: 3%Wahkiakum County: 4%Walla Walla County: 0%Whatcom County: 1%Whitman County: 1%Yakima County: 2%
Expansive clay: share of mapped land where shrink-swell clay limits houses without basementsunder 10%10-25%25-40%40-60%60%+
Adams County: 2%Asotin County: 5%Benton County: 1%Chelan County: 2%Clallam County: 42%Clark County: 22%Columbia County: 4%Cowlitz County: 10%Douglas County: 5%Ferry County: 4%Franklin County: 0%Garfield County: 2%Grant County: 2%Grays Harbor County: 20%Island County: 65%Jefferson County: 39%King County: 38%Kitsap County: 65%Kittitas County: 14%Klickitat County: 5%Lewis County: 20%Lincoln County: 4%Mason County: 45%Okanogan County: 3%Pacific County: 19%Pend Oreille County: 11%Pierce County: 34%San Juan County: 47%Skagit County: 46%Skamania County: 5%Snohomish County: 72%Spokane County: 16%Stevens County: 8%Thurston County: 34%Wahkiakum County: 10%Walla Walla County: 4%Whatcom County: 25%Whitman County: 15%Yakima County: 8%
High water table: share of mapped land where a shallow water table limits basementsunder 10%10-25%25-40%40-60%60%+

Every county in Washington

Select a column heading to sort.
Adams County under 1% 2% 100% 5 1977
Asotin County 29% 5% 100% 1 1976
Benton County 0% 1% 52% 15 1988
Chelan County under 1% 2% 100% 44 1983
Clallam County 1% 42% 98% 4 1982
Clark County 3% 22% 0% 9 1993
Columbia County under 1% 4% 100% 16 1953
Cowlitz County 4% 10% 0% 34 1976
Douglas County under 1% 5% 100% 0 1988
Ferry County under 1% 4% 100% 3 1985
Franklin County 0% under 1% 100% 0 1997
Garfield County 13% 2% 100% 0 1957
Grant County 0% 2% 100% 5 1988
Grays Harbor County 6% 20% 0% 60 1974
Island County 0% 65% 0% 115 1991
Jefferson County 1% 39% 53% 12 1988
King County under 1% 38% 15% 471 1983
Kitsap County under 1% 65% 79% 93 1986
Kittitas County 5% 14% 86% 39 1993
Klickitat County 2% 5% 0% 1 1986
Lewis County 7% 20% 0% 116 1980
Lincoln County 1% 4% 100% 2 1972
Mason County under 1% 45% 22% 54 1989
Okanogan County 0% 3% 100% 23 1982
Pacific County 4% 19% 0% 33 1979
Pend Oreille County 0% 11% 100% 9 1985
Pierce County 2% 34% 0% 152 1986
San Juan County 0% 47% 0% 5 1988
Skagit County under 1% 46% 90% 235 1986
Skamania County 4% 5% 0% 0 1984
Snohomish County 1% 72% 64% 175 1990
Spokane County 3% 16% 100% 14 1978
Stevens County 0% 8% 100% 4 1985
Thurston County 3% 34% 0% 71 1991
Wahkiakum County 4% 10% 0% 1 1978
Walla Walla County 0% 4% 100% 38 1973
Whatcom County 1% 25% 99% 697 1989
Whitman County 1% 15% 100% 6 1977
Yakima County 2% 8% 17% 54 1977

How these shares are counted

Shares are of mapped land in USDA's soil survey (SSURGO), weighted by each soil's share of every map unit. Drought is the US Drought Monitor's D1-or-worse share on the September 22, 2026 map. Flood losses are FEMA NFIP records since 2016. Sources and methods.