Alexandria city, Virginia
A shallow water table limits basements on 44% of Alexandria city's mapped land, a higher share than 62% of US counties. Shrink-swell clay limits houses without basements on 3%.
None of the county is in drought on the October 13, 2026 Drought Monitor map. FEMA's flood data list 199 flood losses here since 2016, 63% of them in buildings with basements. 60% of homes were built before 1980, against 50% nationally; the median home dates from 1974.
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 Alexandria city
| Expansive clay (limits slab homes) | 3.0% |
| High water table (limits basements) | 44.4% |
| Septic fields very limited | 51.0% |
| Clay swell (LEP, by area) | 2.8% |
| High-swell land (LEP 6%+) | 3.0% |
| Urban land, not rated | 46.2% |
| Mapped soil | 9,800 acres |
| Soil series | Share here | Series nationally: high water table |
|---|---|---|
| Kingstowne | 17% | n/a |
| Grist Mill | 16% | n/a |
| Sassafras | 6% | n/a |
| Woodstown | 4% | n/a |
| Neabsco | 3% | n/a |
| Marumsco | 3% | n/a |
How we count · survey areas VA510 (2025-09-05)
What the numbers mean here
On 44% of Alexandria city'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: 32.94 in, 11.12 in below the 1991-2020 average year of 44.06 in.
USDA rates 51% 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. Part of the county was in drought in 41 of the last 52 weeks; the most was 100% of its area, in 35 weeks, most recently on the July 28, 2026 map.
| Category, October 13, 2026 | Share of county |
|---|---|
| D0 abnormally dry or worse | 100% |
| D1 moderate drought or worse | 0% |
| D2 severe or worse | 0% |
| D3 extreme or worse | 0% |
| D4 exceptional | 0% |
Flood losses since 2016
199 flood losses since 2016, $4.2 million paid. The worst year was 2019, with 81. Foundations of the buildings, where recorded: 63% basements, 20% slabs, 1% crawl spaces, 16% elevated. Median water depth outside the building: 14 in.
| Year | Flood losses |
|---|---|
| 2016 | 0 |
| 2017 | 2 |
| 2018 | 16 |
| 2019 | 81 |
| 2020 | 65 |
| 2021 | 26 |
| 2022 | 4 |
| 2023 | 3 |
| 2024 | 1 |
| 2025 | 0 |
| 2026 to date | 1 |
Rain
| Average year, 1991-2020 | 44.06 in |
| 12 months to August 2026 | 32.94 in (-11.12) |
| 2025 | 36.29 in (-7.77) |
| Wettest year since 1895 | 2018: 66.25 in |
| Driest year since 1895 | 1930: 20.31 in |
| Days with 1 inch or more, normal at WASHINGTON REAGAN AP (3 mi away) | 10 |
Homes
| Housing units | 80,844 |
| Median year built | 1974 |
| Built before 1980 | 60% |
| Built 2000 or later | 22% |
| Owner-occupied | 42% |
| Median value, owner-occupied | $735,100 |
| Single-family detached | 14% |
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 |
|---|---|---|---|
| Arlington County, VA | 4 mi | 0% | 3% |
| Falls Church city, VA | 7 mi | 0% | 13% |
| District of Columbia, DC | 7 mi | 0% | 9% |
| Fairfax County, VA | 10 mi | 6% | 33% |
| Fairfax city, VA | 12 mi | 2% | 10% |
| Prince George's County, MD | 13 mi | 1% | 46% |
| Manassas Park city, VA | 20 mi | 0% | 16% |
| Manassas city, VA | 22 mi | 0% | 26% |
Sources: USDA SSURGO (September 5, 2025) · US Drought Monitor (October 13, 2026) · FEMA NFIP v3 (September 9, 2026) · NOAA (August 2026) · Census ACS 2020-2024. Methods · Data status