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Los Angeles County, California
USDA's soil survey flags shrink-swell clay on 4% of Los Angeles County's mapped land and a shallow water table under basements on under 1%, both below the national shares of 15% and 29%. None of the county is in drought on the September 22, 2026 Drought Monitor map.
FEMA's flood data list 891 flood losses here since 2016, 13% of them in buildings with basements. 70% of homes were built before 1980, against 50% nationally; the median home dates from 1965.
Data as of September 22, 2026 · sources
expansive clay: shrink-swell limits slab homes
high water table: limits basements
in drought, September 22, 2026
of homes built before 1980
Soil under Los Angeles County
| Expansive clay (limits slab homes) | 4.2% |
| High water table (limits basements) | under 0.1% |
| Septic fields very limited | 81.4% |
| Clay swell (LEP, by area) | 2.6% |
| High-swell land (LEP 6%+) | 4.0% |
| Urban land, not rated | 10.9% |
| Mapped soil | 3,174,301 acres |
| Soil series | Share here | Series nationally: expansive clay |
|---|---|---|
| Tujunga | 1% | n/a |
| Palmview | 1% | n/a |
| San Emigdio | 1% | n/a |
| Hueneme | 1% | n/a |
| Soboba | 1% | n/a |
| Pico | 1% | n/a |
How we count · survey areas CA669 (2025-09-08), CA676 (2025-09-08), CA696 (2025-09-08), CA772 (2025-09-08), CA776 (2025-09-08)
What the numbers mean here
Rain over the 12 months to August 2026: 20.56 in, 5.46 in above the 1991-2020 average year of 15.10 in.
USDA rates 81% of the land very limited for septic absorption fields.
With shrink-swell clay on 4% and a shallow water table on under 1% of the land, the soil survey points to neither problem across most of Los Angeles County; conditions still vary lot by lot.
Drought
0% of the county is in drought (D1 or worse) on the September 22, 2026 map. Part of the county was in drought in 8 of the last 52 weeks; the most was 100% of its area, in 3 weeks, most recently on the October 14, 2025 map.
| Category, September 22, 2026 | Share of county |
|---|---|
| D0 abnormally dry or worse | 2.7% |
| D1 moderate drought or worse | 0% |
| D2 severe or worse | 0% |
| D3 extreme or worse | 0% |
| D4 exceptional | 0% |
Flood losses since 2016
891 flood losses since 2016, $16.6 million paid. The worst year was 2017, with 220. Foundations of the buildings, where recorded: 13% basements, 61% slabs, 16% crawl spaces, 11% elevated. Median water depth outside the building: 5 in.
| Year | Flood losses |
|---|---|
| 2016 | 63 |
| 2017 | 220 |
| 2018 | 43 |
| 2019 | 86 |
| 2020 | 15 |
| 2021 | 35 |
| 2022 | 24 |
| 2023 | 187 |
| 2024 | 158 |
| 2025 | 46 |
| 2026 to date | 14 |
Rain
| Average year, 1991-2020 | 15.10 in |
| 12 months to August 2026 | 20.56 in (+5.46) |
| 2025 | 20.66 in (+5.56) |
| Wettest year since 1895 | 1983: 34.05 in |
| Driest year since 1895 | 1953: 4.83 in |
| Days with 1 inch or more, normal at BURBANK VALLEY PUMP PLT (5 mi away) | 5.3 |
Homes
| Housing units | 3,650,466 |
| Median year built | 1965 |
| Built before 1980 | 70% |
| Built 2000 or later | 12% |
| Owner-occupied | 46% |
| Median value, owner-occupied | $834,200 |
| Single-family detached | 47% |
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 |
|---|---|---|---|
| Orange County, CA | 45 mi | 14% | 3% |
| Ventura County, CA | 51 mi | 12% | 4% |
| Kern County, CA | 84 mi | 6% | 1% |
| Santa Barbara County, CA | 104 mi | 12% | 4% |
| San Diego County, CA | 118 mi | 17% | 1% |
| San Bernardino County, CA | 127 mi | 1% | under 1% |
| Riverside County, CA | 135 mi | 3% | 5% |
| Tulare County, CA | 143 mi | 14% | 1% |
Sources: USDA SSURGO (September 8, 2025) · US Drought Monitor (September 22, 2026) · FEMA NFIP v3 (September 9, 2026) · NOAA (August 2026) · Census ACS 2020-2024. Methods · Data status