HomeCalifornia

California soil by county

Across California's mapped land, shrink-swell clay limits houses without basements on 13% and a shallow water table limits basements on 7%.

Highest clay shares: Colusa County (55%), Solano County (50%), Contra Costa County (48%), Yolo County (44%), Sutter County (41%). Highest water-table shares: Colusa County (37%), Sutter County (37%), Kings County (33%), Merced County (27%), Butte County (27%).

Data as of September 22, 2026 · 58 counties

Alameda County: 38%Alpine County: 2%Amador County: 1%Butte County: 31%Calaveras County: 2%Colusa County: 55%Contra Costa County: 48%Del Norte County: no dataEl Dorado County: 1%Fresno County: 14%Glenn County: 38%Humboldt County: 10%Imperial County: no dataInyo County: no dataKern County: 6%Kings County: 32%Lake County: 8%Lassen County: 21%Los Angeles County: 4%Madera County: 2%Marin County: 20%Mariposa County: 5%Mendocino County: 9%Merced County: 28%Modoc County: 27%Mono County: 3%Monterey County: 15%Napa County: 14%Nevada County: 2%Orange County: 14%Placer County: 7%Plumas County: 4%Riverside County: 3%Sacramento County: 16%San Benito County: 21%San Bernardino County: 1%San Diego County: 17%San Francisco County: 0%San Joaquin County: 30%San Luis Obispo County: 17%San Mateo County: 10%Santa Barbara County: 12%Santa Clara County: 24%Santa Cruz County: 10%Shasta County: 9%Sierra County: 5%Siskiyou County: 11%Solano County: 50%Sonoma County: 22%Stanislaus County: 24%Sutter County: 41%Tehama County: 15%Trinity County: no dataTulare County: 14%Tuolumne County: 1%Ventura County: 12%Yolo County: 44%Yuba County: 21%
Expansive clay: share of mapped land where shrink-swell clay limits houses without basementsunder 10%10-25%25-40%40-60%60%+
Alameda County: 8%Alpine County: 7%Amador County: 3%Butte County: 27%Calaveras County: 2%Colusa County: 37%Contra Costa County: 11%Del Norte County: no dataEl Dorado County: 2%Fresno County: 2%Glenn County: 15%Humboldt County: 19%Imperial County: no dataInyo County: no dataKern County: 1%Kings County: 33%Lake County: 1%Lassen County: 6%Los Angeles County: 0%Madera County: 3%Marin County: 6%Mariposa County: 3%Mendocino County: 6%Merced County: 27%Modoc County: 15%Mono County: 7%Monterey County: 2%Napa County: 6%Nevada County: 1%Orange County: 3%Placer County: 4%Plumas County: 2%Riverside County: 5%Sacramento County: 26%San Benito County: 4%San Bernardino County: 0%San Diego County: 1%San Francisco County: 3%San Joaquin County: 23%San Luis Obispo County: 1%San Mateo County: 3%Santa Barbara County: 4%Santa Clara County: 3%Santa Cruz County: 1%Shasta County: 4%Sierra County: 9%Siskiyou County: 11%Solano County: 21%Sonoma County: 5%Stanislaus County: 7%Sutter County: 37%Tehama County: 3%Trinity County: no dataTulare County: 1%Tuolumne County: 2%Ventura County: 4%Yolo County: 23%Yuba County: 5%
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 California

Select a column heading to sort.
Alameda County 38% 8% 0% 123 1969
Alpine County 2% 7% 0% 2 1981
Amador County 1% 3% 0% 21 1984
Butte County 31% 27% 0% 71 1981
Calaveras County 2% 2% 0% 34 1986
Colusa County 55% 37% 0% 25 1978
Contra Costa County 48% 11% 0% 178 1978
Del Norte County n/a n/a 39% 4 1981
El Dorado County 1% 2% 3% 64 1983
Fresno County 14% 2% 0% 23 1982
Glenn County 38% 15% 0% 20 1977
Humboldt County 10% 19% 1% 20 1973
Imperial County n/a n/a 55% 2 1988
Inyo County n/a n/a 56% 0 1975
Kern County 6% 1% 4% 69 1984
Kings County 32% 33% 0% 6 1986
Lake County 8% 1% 0% 171 1980
Lassen County 21% 6% 59% 22 1977
Los Angeles County 4% under 1% 0% 891 1965
Madera County 2% 3% 0% 15 1988
Marin County 20% 6% 0% 269 1967
Mariposa County 5% 3% 0% 0 1986
Mendocino County 9% 6% 0% 15 1977
Merced County 28% 27% 0% 242 1986
Modoc County 27% 15% 100% 0 1976
Mono County 3% 7% 0% 4 1980
Monterey County 15% 2% 0% 252 1976
Napa County 14% 6% 0% 29 1976
Nevada County 2% 1% 10% 20 1983
Orange County 14% 3% 0% 227 1977
Placer County 7% 4% 11% 33 1994
Plumas County 4% 2% 5% 16 1981
Riverside County 3% 5% 49% 195 1990
Sacramento County 16% 26% 0% 418 1981
San Benito County 21% 4% 0% 78 1989
San Bernardino County 1% under 1% 53% 121 1983
San Diego County 17% 1% 0% 661 1980
San Francisco County 0% 3% 0% 18 1946
San Joaquin County 30% 23% 0% 109 1984
San Luis Obispo County 17% 1% 0% 138 1983
San Mateo County 10% 3% 0% 240 1966
Santa Barbara County 12% 4% 0% 405 1974
Santa Clara County 24% 3% 0% 260 1975
Santa Cruz County 10% 1% 0% 397 1974
Shasta County 9% 4% 1% 70 1982
Sierra County 5% 9% 22% 7 1971
Siskiyou County 11% 11% 90% 1 1976
Solano County 50% 21% 0% 67 1982
Sonoma County 22% 5% 0% 974 1979
Stanislaus County 24% 7% 0% 26 1981
Sutter County 41% 37% 0% 42 1982
Tehama County 15% 3% 0% 39 1981
Trinity County n/a n/a 6% 1 1977
Tulare County 14% 1% 0% 131 1983
Tuolumne County 1% 2% 0% 11 1980
Ventura County 12% 4% 0% 173 1978
Yolo County 44% 23% 0% 41 1983
Yuba County 21% 5% 0% 27 1986

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.