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Ventura County, California
USDA's soil survey flags shrink-swell clay on 12% of Ventura County's mapped land and a shallow water table under basements on 4%, both below the national shares of 15% and 29%. The soil survey maps 40% of the county's land area; these shares describe the mapped part.
None of the county is in drought on the October 13, 2026 Drought Monitor map. FEMA's flood data list 173 flood losses here since 2016, 3% of them in buildings with basements. 55% of homes were built before 1980, against 50% nationally; the median home dates from 1978.
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 Ventura County
| Expansive clay (limits slab homes) | 11.8% |
| High water table (limits basements) | 4.3% |
| Septic fields very limited | 76.7% |
| Clay swell (LEP, by area) | 3.6% |
| High-swell land (LEP 6%+) | 9.1% |
| Mapped soil | 473,864 acres |
| Soil series | Share here | Series nationally: expansive clay |
|---|---|---|
| San Benito | 6% | n/a |
| Mocho | 5% | n/a |
| Calleguas | 5% | n/a |
| Castaic | 4% | n/a |
| Sorrento | 4% | n/a |
| Nacimiento | 3% | n/a |
How we count · survey areas CA674 (2025-09-08), CA688 (2025-09-08)
What the numbers mean here
Rain over the 12 months to August 2026: 29.08 in, 8.80 in above the 1991-2020 average year of 20.28 in.
USDA rates 77% of the land very limited for septic absorption fields.
With shrink-swell clay on 12% and a shallow water table on 4% of the land, the soil survey points to neither problem across most of Ventura 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 4 of the last 52 weeks; the most was 95.3% of its area, in 4 weeks, most recently on the October 14, 2025 map.
| Category, October 13, 2026 | Share of county |
|---|---|
| D0 abnormally dry or worse | 0% |
| D1 moderate drought or worse | 0% |
| D2 severe or worse | 0% |
| D3 extreme or worse | 0% |
| D4 exceptional | 0% |
Flood losses since 2016
173 flood losses since 2016, $3.3 million paid. The worst year was 2023, with 67. Foundations of the buildings, where recorded: 3% basements, 73% slabs, 11% crawl spaces, 12% elevated. Median water depth outside the building: 7.5 in.
| Year | Flood losses |
|---|---|
| 2016 | 8 |
| 2017 | 28 |
| 2018 | 8 |
| 2019 | 28 |
| 2020 | 0 |
| 2021 | 6 |
| 2022 | 1 |
| 2023 | 67 |
| 2024 | 15 |
| 2025 | 11 |
| 2026 to date | 1 |
Rain
| Average year, 1991-2020 | 20.28 in |
| 12 months to August 2026 | 29.08 in (+8.80) |
| 2025 | 28.33 in (+8.05) |
| Wettest year since 1895 | 1941: 44.01 in |
| Driest year since 1895 | 2013: 4.93 in |
| Days with 1 inch or more, normal at OJAI (8 mi away) | 6.6 |
Homes
| Housing units | 295,878 |
| Median year built | 1978 |
| Built before 1980 | 55% |
| Built 2000 or later | 17% |
| Owner-occupied | 65% |
| Median value, owner-occupied | $822,700 |
| 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 |
|---|---|---|---|
| Los Angeles County, CA | 51 mi | 4% | under 1% |
| Santa Barbara County, CA | 53 mi | 12% | 4% |
| Kern County, CA | 73 mi | 6% | 1% |
| Orange County, CA | 91 mi | 14% | 3% |
| San Luis Obispo County, CA | 103 mi | 17% | 1% |
| Kings County, CA | 125 mi | 32% | 33% |
| Tulare County, CA | 131 mi | 14% | 1% |
| San Diego County, CA | 164 mi | 17% | 1% |
Sources: USDA SSURGO (September 8, 2025) · US Drought Monitor (October 13, 2026) · FEMA NFIP v3 (September 9, 2026) · NOAA (August 2026) · Census ACS 2020-2024. Methods · Data status