Ottawa County, Ohio
A shallow water table limits basements on 75% of Ottawa County's mapped land, a higher share than 85% of US counties. Shrink-swell clay limits houses without basements on 50%.
None of the county is in drought on the October 13, 2026 Drought Monitor map. FEMA's flood data list 127 flood losses here since 2016, 9% of them in buildings with basements. 55% of homes were built before 1980, against 50% nationally; the median home dates from 1976.
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 Ottawa County
| Expansive clay (limits slab homes) | 49.7% |
| High water table (limits basements) | 74.5% |
| Septic fields very limited | 78.8% |
| Clay swell (LEP, by area) | 5.6% |
| High-swell land (LEP 6%+) | 37.4% |
| Mapped soil | 188,665 acres |
| Soil series | Share here | Series nationally: high water table |
|---|---|---|
| Toledo | 34% | n/a |
| Nappanee | 16% | n/a |
| Hoytville | 10% | 99% |
| Lenawee | 4% | n/a |
| Castalia | 3% | n/a |
| Fulton | 2% | n/a |
How we count · survey areas OH123 (2025-09-02)
What the numbers mean here
Clay swell averages a linear extensibility of 5.6% by land area here, and 37% of the land reaches USDA's high class (6% or more). Clay like that swells when wet and shrinks when dry, under 50% of the mapped land.
On 75% of Ottawa 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: 34.08 in, 0.65 in below the 1991-2020 average year of 34.73 in.
USDA rates 79% 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 100% of its area, in 3 weeks, most recently on the November 4, 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
127 flood losses since 2016, $2.4 million paid. The worst year was 2018, with 33. Foundations of the buildings, where recorded: 9% basements, 45% slabs, 40% crawl spaces, 5% elevated. Median water depth outside the building: 9 in.
| Year | Flood losses |
|---|---|
| 2016 | 2 |
| 2017 | 6 |
| 2018 | 33 |
| 2019 | 28 |
| 2020 | 15 |
| 2021 | 24 |
| 2022 | 0 |
| 2023 | 12 |
| 2024 | 1 |
| 2025 | 0 |
| 2026 to date | 6 |
Rain
| Average year, 1991-2020 | 34.73 in |
| 12 months to August 2026 | 34.08 in (-0.65) |
| 2025 | 29.75 in (-4.98) |
| Wettest year since 1895 | 2011: 53.16 in |
| Driest year since 1895 | 1963: 19.76 in |
| Days with 1 inch or more, normal at FREMONT (16 mi away) | 7.9 |
Homes
| Housing units | 28,911 |
| Median year built | 1976 |
| Built before 1980 | 55% |
| Built 2000 or later | 19% |
| Owner-occupied | 84% |
| Median value, owner-occupied | $219,900 |
| Single-family detached | 73% |
What repairs cost
Published ranges from cost guides, not quotes. More sources, and where they disagree.
Cities in Ottawa County
| City | Expansive clay | High water table | Homes |
|---|---|---|---|
| Clay Center | 49% | 65% | 137 |
| Elmore | 4% | 76% | 680 |
| Genoa | 55% | 78% | 887 |
| Marblehead | 1% | 15% | 1,128 |
| Oak Harbor | 51% | 77% | 1,243 |
| Port Clinton | 53% | 62% | 3,711 |
| Put-in-Bay | 0% | 10% | 295 |
| Rocky Ridge | 65% | 88% | 122 |
Nearby counties
| Place | Distance | Expansive clay | High water table |
|---|---|---|---|
| Sandusky County, OH | 15 mi | 35% | 80% |
| Erie County, OH | 24 mi | 6% | 69% |
| Lucas County, OH | 25 mi | 19% | 68% |
| Seneca County, OH | 30 mi | 26% | 89% |
| Wood County, OH | 34 mi | 55% | 91% |
| Huron County, OH | 35 mi | 2% | 90% |
| Monroe County, MI | 35 mi | 11% | 91% |
| Lorain County, OH | 44 mi | 3% | 91% |
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