Roberts County, South Dakota

A shallow water table limits basements on 60% of Roberts County's mapped land, a higher share than 74% of US counties and the 7th highest of 66 South Dakota counties. Shrink-swell clay limits houses without basements on 26%.

100% of the county is in drought on the October 13, 2026 Drought Monitor map. FEMA's flood data list 9 flood losses here since 2016. 62% of homes were built before 1980, against 50% nationally; the median home dates from 1974.

Data as of October 13, 2026 · sources

26%

expansive clay: shrink-swell limits slab homes

60%

high water table: limits basements

100%

in drought, October 13, 2026

62%

of homes built before 1980

Soil under Roberts County

Expansive clay (limits slab homes)	26.2%
High water table (limits basements)	60.2%
Septic fields very limited	83.8%
Clay swell (LEP, by area)	4.7%
High-swell land (LEP 6%+)	27.9%
Mapped soil	726,445 acres

Soil series	Share here	Series nationally: high water table
Forman	15%	n/a
Peever	12%	n/a
Heimdal	6%	n/a
Aastad	6%	n/a
Tonka	4%	n/a
Buse	4%	n/a

Roberts 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 SD109 (2025-09-10)

What the numbers mean here

Clay swell averages a linear extensibility of 4.7% by land area here, and 28% 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.

Clay shrinks as it dries: 100% of the county is in drought on the latest map, and 26% of Roberts County's mapped land has shrink-swell clay.

On 60% of Roberts 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: 20.55 in, 4.15 in below the 1991-2020 average year of 24.70 in.

USDA rates 84% 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 12 of the last 52 weeks; the most was 100% 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	100%
D1 moderate drought or worse	100%
D2 severe or worse	14.1%
D3 extreme or worse	0%
D4 exceptional	0%

Flood losses since 2016

9 flood losses since 2016, $179,796 paid. The worst year was 2023, with 4.

Year	Flood losses
2016	0
2017	0
2018	0
2019	2
2020	1
2021	0
2022	0
2023	4
2024	0
2025	2
2026 to date	0

Rain

Average year, 1991-2020	24.70 in
12 months to August 2026	20.55 in (-4.15)
2025	28.67 in (+3.97)
Wettest year since 1895	2019: 34.41 in
Driest year since 1895	1976: 8.60 in
Days with 1 inch or more, normal at SISSETON (5 mi away)	5.6

Homes

Housing units	4,848
Median year built	1974
Built before 1980	62%
Built 2000 or later	19%
Owner-occupied	71%
Median value, owner-occupied	$154,500
Single-family detached	80%

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
Traverse County, MN	25 mi	21%	94%
Big Stone County, MN	30 mi	15%	73%
Marshall County, SD	32 mi	22%	57%
Grant County, SD	32 mi	26%	56%
Day County, SD	36 mi	19%	63%
Richland County, ND	44 mi	29%	90%
Stevens County, MN	46 mi	11%	75%
Sargent County, ND	47 mi	16%	71%

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