HomeSouth DakotaLyman County

Lyman County, South Dakota

Shrink-swell clay limits houses without basements on 89% of Lyman County's mapped land, a higher share than 100% of US counties and the 2nd highest of 66 South Dakota counties. A shallow water table limits basements on 8%.

0.3% of the county is in drought on the October 13, 2026 Drought Monitor map. FEMA's flood data list 13 flood losses here since 2016. 59% of homes were built before 1980, against 50% nationally; the median home dates from 1976.

Data as of October 13, 2026 · sources

89%

expansive clay: shrink-swell limits slab homes

8%

high water table: limits basements

0%

in drought, October 13, 2026

59%

of homes built before 1980

Soil under Lyman County

Expansive clay (limits slab homes)89.3%
High water table (limits basements)8.4%
Septic fields very limited89.1%
Clay swell (LEP, by area)11.5%
High-swell land (LEP 6%+)89.2%
Mapped soil1,079,043 acres
Soil seriesShare hereSeries nationally: expansive clay
Millboro24%n/a
Opal14%n/a
Promise11%n/a
Sansarc11%n/a
Bullcreek4%n/a
Capa3%n/a
Buffalo County: 43%Hughes County: 34%Tripp County: 61%Brule County: 43%Jones County: 94%Hyde County: 41%Mellette County: 61%Stanley County: 89%Lyman County BuffaloHughesTrippBruleJonesHydeMelletteStanleyLyman
Lyman County (heavy outline) and nearby counties, shaded by expansive clay share.under 10%10-25%25-40%40-60%60%+

How we count · survey areas SD085 (2025-09-10)

What the numbers mean here

Clay swell averages a linear extensibility of 11.5% by land area here, and 89% of the land reaches USDA's high class (6% or more). Clay like that swells when wet and shrinks when dry, under 89% of the mapped land.

Rain over the 12 months to August 2026: 20.00 in, 1.33 in below the 1991-2020 average year of 21.33 in.

USDA rates 89% of the land very limited for septic absorption fields.

Drought

0.3% of the county is in drought (D1 or worse) on the October 13, 2026 map. Part of the county was in drought in 39 of the last 52 weeks; the most was 100% of its area, in 3 weeks, most recently on the June 2, 2026 map.

October 21, 2025Share of area in drought, weeklyOctober 13, 2026
Category, October 13, 2026Share of county
D0 abnormally dry or worse18.2%
D1 moderate drought or worse0.3%
D2 severe or worse0%
D3 extreme or worse0%
D4 exceptional0%

Flood losses since 2016

13 flood losses since 2016, $275,574 paid. The worst year was 2019, with 13.

YearFlood losses
20160
20170
20180
201913
20200
20210
20220
20230
20240
20250
2026 to date0

Rain

Average year, 1991-202021.33 in
12 months to August 202620.00 in (-1.33)
202521.09 in (-0.24)
Wettest year since 18952019: 33.68 in
Driest year since 18951976: 9.17 in
Days with 1 inch or more, normal at KENNEBEC (1 mi away)4.3

Homes

Housing units1,553
Median year built1976
Built before 198059%
Built 2000 or later17%
Owner-occupied70%
Median value, owner-occupied$165,800
Single-family detached81%

What repairs cost

Published ranges from cost guides, not quotes. More sources, and where they disagree.

WorkRangeSource
Foundation repair, US $2,200 to $8,200 Fixr, January 27, 2026
Pier-and-beam repair, US $2,000 to $15,000 Fixr, January 27, 2026
Foundation inspection, US $300 to $600 Fixr, January 31, 2025

Nearby counties

PlaceDistanceExpansive clayHigh water table
Buffalo County, SD 33 mi 43% 12%
Hughes County, SD 34 mi 34% 8%
Tripp County, SD 38 mi 61% 9%
Brule County, SD 39 mi 43% 12%
Jones County, SD 42 mi 94% 7%
Hyde County, SD 48 mi 41% 13%
Mellette County, SD 50 mi 61% 3%
Stanley County, SD 57 mi 89% 6%

Sources: USDA SSURGO (September 10, 2025) · US Drought Monitor (October 13, 2026) · FEMA NFIP v3 (September 9, 2026) · NOAA (August 2026) · Census ACS 2020-2024. Methods · Data status