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Merced County, California
Shrink-swell clay limits houses without basements on 28% of Merced County's mapped land, a higher share than 78% of US counties. A shallow water table limits basements on 27%.
None of the county is in drought on the October 13, 2026 Drought Monitor map. FEMA's flood data list 242 flood losses here since 2016, 1% of them in buildings with basements. 41% of homes were built before 1980, against 50% nationally; the median home dates from 1986.
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 Merced County
| Expansive clay (limits slab homes) | 27.9% |
| High water table (limits basements) | 27.4% |
| Septic fields very limited | 79.6% |
| Clay swell (LEP, by area) | 4.6% |
| High-swell land (LEP 6%+) | 28.3% |
| Mapped soil | 1,255,329 acres |
| Soil series | Share here | Series nationally: expansive clay |
|---|---|---|
| Delhi | 4% | n/a |
| Woo | 3% | n/a |
| Atwater | 3% | n/a |
| Arburua | 3% | n/a |
| Fresno | 3% | n/a |
| Lewis | 2% | n/a |
How we count · survey areas CA647 (2025-09-02), CA648 (2025-09-02)
What the numbers mean here
Clay swell averages a linear extensibility of 4.6% by land area here, and 28% of the land reaches USDA's high class (6% or more). Clay like that swells when wet and shrinks when dry, under 28% of the mapped land.
On 27% of Merced County's mapped land, soil stays saturated within about 6 feet of the surface for part of the year, which is basement depth.
Rain over the 12 months to August 2026: 11.74 in, 0.22 in above the 1991-2020 average year of 11.52 in.
USDA rates 80% of the land very limited for septic absorption fields.
Drought
0% of the county is in drought (D1 or worse) on the October 13, 2026 map. No part of the county was in drought in the last 52 weeks.
| Category, October 13, 2026 | Share of county |
|---|---|
| D0 abnormally dry or worse | 19.6% |
| D1 moderate drought or worse | 0% |
| D2 severe or worse | 0% |
| D3 extreme or worse | 0% |
| D4 exceptional | 0% |
Flood losses since 2016
242 flood losses since 2016, $10.4 million paid. The worst year was 2023, with 203. Foundations of the buildings, where recorded: 1% basements, 53% slabs, 39% crawl spaces, 6% elevated. Median water depth outside the building: 10 in.
| Year | Flood losses |
|---|---|
| 2016 | 5 |
| 2017 | 9 |
| 2018 | 8 |
| 2019 | 0 |
| 2020 | 1 |
| 2021 | 3 |
| 2022 | 4 |
| 2023 | 203 |
| 2024 | 4 |
| 2025 | 2 |
| 2026 to date | 3 |
Rain
| Average year, 1991-2020 | 11.52 in |
| 12 months to August 2026 | 11.74 in (+0.22) |
| 2025 | 11.47 in (-0.05) |
| Wettest year since 1895 | 1983: 22.33 in |
| Driest year since 1895 | 2013: 3.50 in |
| Days with 1 inch or more, normal at LOS BANOS (12 mi away) | 0.5 |
Homes
| Housing units | 90,872 |
| Median year built | 1986 |
| Built before 1980 | 41% |
| Built 2000 or later | 30% |
| Owner-occupied | 54% |
| Median value, owner-occupied | $391,800 |
| Single-family detached | 74% |
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 |
|---|---|---|---|
| Stanislaus County, CA | 30 mi | 24% | 7% |
| San Benito County, CA | 45 mi | 21% | 4% |
| Mariposa County, CA | 52 mi | 5% | 3% |
| Santa Clara County, CA | 53 mi | 24% | 3% |
| Madera County, CA | 54 mi | 2% | 3% |
| San Joaquin County, CA | 59 mi | 30% | 23% |
| Fresno County, CA | 66 mi | 14% | 2% |
| Calaveras County, CA | 70 mi | 2% | 2% |
Sources: USDA SSURGO (September 2, 2025) · US Drought Monitor (October 13, 2026) · FEMA NFIP v3 (September 9, 2026) · NOAA (August 2026) · Census ACS 2020-2024. Methods · Data status