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Yankton County, South Dakota

A shallow water table limits basements on 30% of Yankton County's mapped land. Shrink-swell clay limits houses without basements on 21%.

100% of the county is in drought on the October 13, 2026 Drought Monitor map. FEMA's flood data list 16 flood losses here since 2016. 55% of homes were built before 1980, against 50% nationally; the median home dates from 1977.

Data as of October 13, 2026 · sources

21%

expansive clay: shrink-swell limits slab homes

30%

high water table: limits basements

100%

in drought, October 13, 2026

55%

of homes built before 1980

Soil under Yankton County

Expansive clay (limits slab homes)20.8%
High water table (limits basements)29.9%
Septic fields very limited91.0%
Clay swell (LEP, by area)4.8%
High-swell land (LEP 6%+)23.9%
Mapped soil339,104 acres
Soil seriesShare hereSeries nationally: high water table
Clarno21%0%
Ethan10%n/a
Egan7%n/a
Bonilla7%n/a
Crossplain5%n/a
Betts4%n/a
Clay County: 53%Turner County: 39%Bon Homme County: 26%Cedar County: 7%Hutchinson County: 25%Knox County: 6%Lincoln County: 51%Union County: 42%Yankton County ClayTurnerBon HommeCedarHutchinsonKnoxLincolnUnionYankton
Yankton County (heavy outline) and nearby counties, shaded by high water table share.under 10%10-25%25-40%40-60%60%+

How we count · survey areas SD135 (2025-09-10)

What the numbers mean here

Clay swell averages a linear extensibility of 4.8% by land area here, and 24% of the land reaches USDA's high class (6% or more). Clay like that swells when wet and shrinks when dry, under 21% of the mapped land.

Clay shrinks as it dries: 100% of the county is in drought on the latest map, and 21% of Yankton County's mapped land has shrink-swell clay.

On 30% of Yankton 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: 14.63 in, 12.98 in below the 1991-2020 average year of 27.61 in.

USDA rates 91% of the land very limited for septic absorption fields.

Drought

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

October 21, 2025Share of area in drought, weeklyOctober 13, 2026
Category, October 13, 2026Share of county
D0 abnormally dry or worse100%
D1 moderate drought or worse100%
D2 severe or worse0%
D3 extreme or worse0%
D4 exceptional0%

Flood losses since 2016

16 flood losses since 2016, $1.3 million paid. The worst year was 2019, with 13.

YearFlood losses
20160
20170
20183
201913
20200
20210
20220
20230
20240
20250
2026 to date0

Rain

Average year, 1991-202027.61 in
12 months to August 202614.63 in (-12.98)
202525.84 in (-1.77)
Wettest year since 18951944: 39.71 in
Driest year since 18951980: 14.83 in
Days with 1 inch or more, normal at YANKTON 2 E (9 mi away)6.7

Homes

Housing units10,616
Median year built1977
Built before 198055%
Built 2000 or later22%
Owner-occupied73%
Median value, owner-occupied$225,900
Single-family detached70%

What repairs cost

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

WorkRangeSource
Basement waterproofing, US $3,000 to $10,000 Fixr, February 6, 2026
Sump pump installation, US $800 to $2,000 Fixr, January 31, 2025
Crawl space encapsulation, US $2,000 to $8,000 Fixr, August 29, 2025

Nearby counties

PlaceDistanceExpansive clayHigh water table
Clay County, SD 22 mi 29% 53%
Turner County, SD 24 mi 20% 39%
Bon Homme County, SD 25 mi 27% 26%
Cedar County, NE 29 mi 2% 7%
Hutchinson County, SD 29 mi 21% 25%
Knox County, NE 36 mi 16% 6%
Lincoln County, SD 39 mi 28% 51%
Union County, SD 39 mi 33% 42%

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