New Castle County, Delaware
A shallow water table limits basements on 34% of New Castle County's mapped land, a higher share than 52% of US counties and the 3rd highest of 3 Delaware counties. Shrink-swell clay limits houses without basements on 2%.
None of the county is in drought on the October 13, 2026 Drought Monitor map. FEMA's flood data list 229 flood losses here since 2016, 39% of them in buildings with basements. 56% of homes were built before 1980, against 50% nationally; the median home dates from 1975.
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 New Castle County
| Expansive clay (limits slab homes) | 1.7% |
| High water table (limits basements) | 34.0% |
| Septic fields very limited | 59.1% |
| Clay swell (LEP, by area) | 1.9% |
| High-swell land (LEP 6%+) | 1.5% |
| Urban land, not rated | 9.2% |
| Mapped soil | 279,235 acres |
| Soil series | Share here | Series nationally: high water table |
|---|---|---|
| Reybold | 10% | n/a |
| Glenelg | 5% | 0% |
| Fallsington | 5% | n/a |
| Sassafras | 4% | n/a |
| Mattapex | 3% | n/a |
| Hammonton | 3% | n/a |
How we count · survey areas DE003 (2025-09-09)
What the numbers mean here
On 34% of New Castle 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: 37.36 in, 8.79 in below the 1991-2020 average year of 46.15 in.
USDA rates 59% 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 44 of the last 52 weeks; the most was 100% of its area, in 11 weeks, most recently on the July 7, 2026 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
229 flood losses since 2016, $10.0 million paid. The worst year was 2021, with 106. Foundations of the buildings, where recorded: 39% basements, 20% slabs, 3% crawl spaces, 38% elevated. Median water depth outside the building: 19 in.
| Year | Flood losses |
|---|---|
| 2016 | 9 |
| 2017 | 6 |
| 2018 | 11 |
| 2019 | 2 |
| 2020 | 56 |
| 2021 | 106 |
| 2022 | 6 |
| 2023 | 10 |
| 2024 | 11 |
| 2025 | 8 |
| 2026 to date | 4 |
Rain
| Average year, 1991-2020 | 46.15 in |
| 12 months to August 2026 | 37.36 in (-8.79) |
| 2025 | 38.37 in (-7.78) |
| Wettest year since 1895 | 2018: 64.29 in |
| Driest year since 1895 | 1965: 27.55 in |
| Days with 1 inch or more, normal at WILMINGTON NEW CASTLE CO AP (7 mi away) | 11.8 |
Homes
| Housing units | 236,079 |
| Median year built | 1975 |
| Built before 1980 | 56% |
| Built 2000 or later | 20% |
| Owner-occupied | 69% |
| Median value, owner-occupied | $352,200 |
| Single-family detached | 53% |
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 |
|---|---|---|---|
| Salem County, NJ | 15 mi | 2% | 54% |
| Cecil County, MD | 16 mi | 2% | 38% |
| Delaware County, PA | 27 mi | under 1% | 22% |
| Chester County, PA | 28 mi | under 1% | 21% |
| Gloucester County, NJ | 28 mi | 2% | 34% |
| Cumberland County, NJ | 33 mi | 0% | 50% |
| Kent County, DE | 34 mi | 0% | 77% |
| Kent County, MD | 35 mi | 0% | 54% |
Sources: USDA SSURGO (September 9, 2025) · US Drought Monitor (October 13, 2026) · FEMA NFIP v3 (September 9, 2026) · NOAA (August 2026) · Census ACS 2020-2024. Methods · Data status