Seneca County, Ohio
A shallow water table limits basements on 89% of Seneca County's mapped land, a higher share than 95% of US counties. Shrink-swell clay limits houses without basements on 26%.
None of the county is in drought on the October 13, 2026 Drought Monitor map. FEMA's flood data list 7 flood losses here since 2016. 76% of homes were built before 1980, against 50% nationally; the median home dates from 1959.
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 Seneca County
| Expansive clay (limits slab homes) | 26.2% |
| High water table (limits basements) | 88.9% |
| Septic fields very limited | 95.9% |
| Clay swell (LEP, by area) | 4.4% |
| High-swell land (LEP 6%+) | 7.6% |
| Mapped soil | 353,926 acres |
How we count · survey areas OH147 (2025-09-08)
What the numbers mean here
Clay swell averages a linear extensibility of 4.4% by land area here, and 8% of the land reaches USDA's high class (6% or more). Clay like that swells when wet and shrinks when dry, under 26% of the mapped land.
On 89% of Seneca 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: 35.81 in, 1.93 in below the 1991-2020 average year of 37.74 in.
USDA rates 96% 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 24 of the last 52 weeks; the most was 99% of its area, in 2 weeks, most recently on the October 28, 2025 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
7 flood losses since 2016, $236,557 paid. The worst year was 2017, with 4.
| Year | Flood losses |
|---|---|
| 2016 | 0 |
| 2017 | 4 |
| 2018 | 0 |
| 2019 | 0 |
| 2020 | 0 |
| 2021 | 1 |
| 2022 | 0 |
| 2023 | 0 |
| 2024 | 0 |
| 2025 | 0 |
| 2026 to date | 2 |
Rain
| Average year, 1991-2020 | 37.74 in |
| 12 months to August 2026 | 35.81 in (-1.93) |
| 2025 | 35.01 in (-2.73) |
| Wettest year since 1895 | 2011: 57.72 in |
| Driest year since 1895 | 1963: 22.52 in |
| Days with 1 inch or more, normal at FREMONT (15 mi away) | 7.9 |
Homes
| Housing units | 23,982 |
| Median year built | 1959 |
| Built before 1980 | 76% |
| Built 2000 or later | 9% |
| Owner-occupied | 73% |
| Median value, owner-occupied | $154,700 |
| Single-family detached | 79% |
What repairs cost
Published ranges from cost guides, not quotes. More sources, and where they disagree.
Cities in Seneca County
| City | Expansive clay | High water table | Homes |
|---|---|---|---|
| Attica | 15% | 98% | 353 |
| Bettsville | 32% | 59% | 253 |
| Bloomville | 8% | 99% | 296 |
| Fostoria | 43% | 73% | 5,793 |
| New Riegel | 18% | 100% | 116 |
| Republic | 18% | 99% | 199 |
| Tiffin | 15% | 72% | 8,130 |
Nearby counties
| Place | Distance | Expansive clay | High water table |
|---|---|---|---|
| Sandusky County, OH | 16 mi | 35% | 80% |
| Crawford County, OH | 22 mi | 3% | 93% |
| Wyandot County, OH | 22 mi | 30% | 90% |
| Huron County, OH | 28 mi | 2% | 90% |
| Hancock County, OH | 29 mi | 33% | 93% |
| Ottawa County, OH | 30 mi | 50% | 75% |
| Wood County, OH | 31 mi | 55% | 91% |
| Erie County, OH | 34 mi | 6% | 69% |
Sources: USDA SSURGO (September 8, 2025) · US Drought Monitor (October 13, 2026) · FEMA NFIP v3 (September 9, 2026) · NOAA (August 2026) · Census ACS 2020-2024. Methods · Data status