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Assumption Parish, Louisiana

A shallow water table limits basements on 88% of Assumption Parish's mapped land, a higher share than 95% of US counties and the 8th highest of 64 Louisiana counties. Shrink-swell clay limits houses without basements on 68%.

100% of the county is in drought on the October 13, 2026 Drought Monitor map, up from 0% a week earlier. FEMA's flood data list 64 flood losses here since 2016, 0% of them in buildings with basements. 45% of homes were built before 1980, against 50% nationally; the median home dates from 1983.

Data as of October 13, 2026 · sources

68%

expansive clay: shrink-swell limits slab homes

88%

high water table: limits basements

100%

in drought, October 13, 2026

45%

of homes built before 1980

Soil under Assumption Parish

Expansive clay (limits slab homes)67.5%
High water table (limits basements)88.3%
Septic fields very limited88.3%
Clay swell (LEP, by area)13.2%
High-swell land (LEP 6%+)67.5%
Mapped soil234,600 acres
Soil seriesShare hereSeries nationally: high water table
Barbary29%n/a
Cancienne20%n/a
Schriever16%n/a
Fausse15%n/a
Thibaut8%n/a
Gramercy2%n/a
St. James Parish: 92%Ascension Parish: 91%St. Mary Parish: 80%Iberville Parish: 88%St. Martin Parish: 84%St. John the Baptist Parish: 61%West Baton Rouge Parish: 81%Terrebonne Parish: 65%Assumption Parish St. JamesAscensionSt. MaryIbervilleSt. MartinSt. John the BaptistWest Baton RougeTerrebonneAssumption
Assumption Parish (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 LA007 (2025-08-28)

What the numbers mean here

Clay swell averages a linear extensibility of 13.2% by land area here, and 68% of the land reaches USDA's high class (6% or more). Clay like that swells when wet and shrinks when dry, under 68% of the mapped land.

Clay shrinks as it dries: 100% of the county is in drought on the latest map, and 68% of Assumption Parish's mapped land has shrink-swell clay.

On 88% of Assumption Parish'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: 52.65 in, 9.68 in below the 1991-2020 average year of 62.33 in.

USDA rates 88% 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 26 of the last 52 weeks; the most was 100% of its area, in 7 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

64 flood losses since 2016, $1.3 million paid. The worst year was 2021, with 21. Foundations of the buildings, where recorded: 53% slabs, 9% crawl spaces, 38% elevated. Median water depth outside the building: 7 in.

YearFlood losses
20163
20178
20184
201916
20200
202121
20220
20230
202412
20250
2026 to date0

Rain

Average year, 1991-202062.33 in
12 months to August 202652.65 in (-9.68)
202552.24 in (-10.09)
Wettest year since 18951991: 87.05 in
Driest year since 18951924: 39.44 in
Days with 1 inch or more, normal at NAPOLEONVILLE (4 mi away)21.2

Homes

Housing units10,066
Median year built1983
Built before 198045%
Built 2000 or later25%
Owner-occupied85%
Median value, owner-occupied$150,300
Single-family detached63%

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
St. James Parish, LA 18 mi 68% 92%
Ascension Parish, LA 23 mi 46% 91%
St. Mary Parish, LA 31 mi 52% 80%
Iberville Parish, LA 31 mi 54% 88%
St. Martin Parish, LA 36 mi 57% 84%
St. John the Baptist Parish, LA 38 mi 43% 61%
West Baton Rouge Parish, LA 42 mi 44% 81%
Terrebonne Parish, LA 42 mi 34% 65%

Sources: USDA SSURGO (August 28, 2025) · US Drought Monitor (October 13, 2026) · FEMA NFIP v3 (September 9, 2026) · NOAA (August 2026) · Census ACS 2020-2024. Methods · Data status