Alvin, Texas
Inside Alvin's city limits, shrink-swell clay limits houses without basements on 65% of mapped land, higher than 70% of Texas cities. A shallow water table limits basements on 48%.
That clay share is close to Brazoria County's 64%. FEMA's flood data list 1,377 flood losses since 2016 in the 2 ZIP codes overlapping the city. Of its 12,327 homes, 43% were built before 1980; the median dates from 1985.
Data as of October 13, 2026 · sources · in Brazoria County
expansive clay: shrink-swell limits slab homes
high water table: limits basements
flood losses since 2016 in 2 overlapping ZIPs
of homes built before 1980
Foundation repair in Alvin
Foundation repair in Alvin: shrink-swell clay limits slab homes on 65% of Alvin's mapped land, more than in 70% of Texas cities.
About 7,000 of Alvin's 12,327 homes are detached houses.
| Who designs the repair | The ASCE Texas Section's repair guidelines say a Texas-licensed engineer should evaluate the foundation and design the repair (2022 guidelines) |
| Prices | Cost guide ranges compared |
Soil under Alvin city limits
| Expansive clay (limits slab homes) | 64.7% |
| High water table (limits basements) | 48.2% |
| Septic fields very limited | 84.4% |
| Clay swell (LEP, by area) | 9.3% |
| High-swell land (LEP 6%+) | 63.0% |
| Urban land, not rated | 2.4% |
| Mapped soil | 15,274 acres |
| Soil series | Share here | Series nationally: expansive clay |
|---|---|---|
| Lake Charles | 48% | 97% |
| Bernard | 27% | 43% |
| Edna | 10% | n/a |
| Aris | 3% | n/a |
| Leton | 2% | n/a |
| Verland | 1% | n/a |
What the numbers mean here
Clay swell averages a linear extensibility of 9.3% by land area here, and 63% of the land reaches USDA's high class (6% or more). Clay like that swells when wet and shrinks when dry, under 65% of the mapped land.
Clay shrinks as it dries: 100% of Brazoria County is in drought on the latest map, and 65% of Alvin's mapped land has shrink-swell clay.
On 48% of Alvin's mapped land, soil stays saturated within about 6 feet of the surface for part of the year, which is basement depth.
USDA rates 84% of the land very limited for septic absorption fields.
Drought in Brazoria County
100% of Brazoria County is in drought (D1 or worse) on the October 13, 2026 map. County detail.
Flood losses by ZIP code
FEMA flood records since 2016 in the ZIP codes that overlap Alvin. ZIP areas reach past city limits.
| ZIP | Share of city land | Flood losses | Paid |
|---|---|---|---|
| 77511 | 67% | 974 | $67.4 million |
| 77583 | 29% | 403 | $23.5 million |
Homes in Alvin
| Housing units | 12,327 |
| Median year built | 1985 |
| Built before 1980 | 43% |
| Built 2000 or later | 30% |
| Owner-occupied | 61% |
| Median value, owner-occupied | $228,700 |
| Single-family detached | 56% |
Nearby cities
| Place | Distance | Expansive clay | High water table |
|---|---|---|---|
| Hillcrest Village | 2 mi | 48% | 78% |
| Friendswood | 6 mi | 74% | 49% |
| Santa Fe | 8 mi | 6% | 92% |
| League City | 8 mi | 42% | 71% |
| Liverpool | 9 mi | 84% | 33% |
| Manvel | 10 mi | 70% | 47% |
| Webster | 10 mi | 56% | 26% |
| Dickinson | 10 mi | 66% | 74% |
Sources: USDA SSURGO (August 5, 2026) · US Drought Monitor (October 13, 2026) · FEMA NFIP v3 (September 9, 2026) · Census ACS 2020-2024. Methods · Data status