Brown County, South Dakota

A shallow water table limits basements on 56% of Brown County's mapped land, a higher share than 71% of US counties and the 9th highest of 66 South Dakota counties. Shrink-swell clay limits houses without basements on 28%.

2.3% of the county is in drought on the October 13, 2026 Drought Monitor map. FEMA's flood data list 4 flood losses here since 2016. 60% of homes were built before 1980, against 50% nationally; the median home dates from 1973.

Data as of October 13, 2026 · sources

28%

expansive clay: shrink-swell limits slab homes

56%

high water table: limits basements

in drought, October 13, 2026

60%

of homes built before 1980

Soil under Brown County

Expansive clay (limits slab homes)	28.4%
High water table (limits basements)	56.1%
Septic fields very limited	53.9%
Clay swell (LEP, by area)	4.7%
High-swell land (LEP 6%+)	33.5%
Mapped soil	1,107,891 acres

Soil series	Share here	Series nationally: high water table
Barnes	8%	20%
Beotia	7%	n/a
Great Bend	6%	n/a
Tonka	4%	n/a
Harmony	4%	n/a
Aberdeen	4%	n/a

Brown 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 SD013 (2025-09-10)

What the numbers mean here

Clay swell averages a linear extensibility of 4.7% by land area here, and 34% of the land reaches USDA's high class (6% or more). Clay like that swells when wet and shrinks when dry, under 28% of the mapped land.

Clay shrinks as it dries: 2.3% of the county is in drought on the latest map, and 28% of Brown County's mapped land has shrink-swell clay.

On 56% of Brown 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: 19.57 in, 2.35 in below the 1991-2020 average year of 21.92 in.

USDA rates 54% of the land very limited for septic absorption fields.

Drought

2.3% of the county is in drought (D1 or worse) on the October 13, 2026 map. Part of the county was in drought in 3 of the last 52 weeks; the most was 2.3% of its area, in 3 weeks, most recently on the October 13, 2026 map.

October 21, 2025Share of area in drought, weeklyOctober 13, 2026

Category, October 13, 2026	Share of county
D0 abnormally dry or worse	26.3%
D1 moderate drought or worse	2.3%
D2 severe or worse	0%
D3 extreme or worse	0%
D4 exceptional	0%

Flood losses since 2016

4 flood losses since 2016, $2,614 paid. The worst year was 2022, with 2.

Year	Flood losses
2016	0
2017	0
2018	0
2019	2
2020	0
2021	0
2022	2
2023	0
2024	0
2025	0
2026 to date	0

Rain

Average year, 1991-2020	21.92 in
12 months to August 2026	19.57 in (-2.35)
2025	24.27 in (+2.35)
Wettest year since 1895	1896: 31.31 in
Driest year since 1895	1976: 9.54 in
Days with 1 inch or more, normal at COLUMBIA 8 N (10 mi away)	4.8

Homes

Housing units	18,090
Median year built	1973
Built before 1980	60%
Built 2000 or later	23%
Owner-occupied	68%
Median value, owner-occupied	$221,100
Single-family detached	63%

What repairs cost

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

Work	Range	Source
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

Place	Distance	Expansive clay	High water table
Dickey County, ND	36 mi	20%	60%
Marshall County, SD	39 mi	22%	57%
Day County, SD	41 mi	19%	63%
Edmunds County, SD	43 mi	22%	25%
McPherson County, SD	45 mi	18%	22%
Spink County, SD	46 mi	45%	56%
Sargent County, ND	50 mi	16%	71%
Faulk County, SD	53 mi	20%	23%

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