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St. Charles Parish, Louisiana

A shallow water table limits basements on 63% of St. Charles Parish's mapped land, a higher share than 76% of US counties. Shrink-swell clay limits houses without basements on 44%.

4.5% 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 1,631 flood losses here since 2016, under 1% of them in buildings with basements. 36% of homes were built before 1980, against 50% nationally; the median home dates from 1986.

Data as of October 13, 2026 · sources

44%

expansive clay: shrink-swell limits slab homes

63%

high water table: limits basements

5%

in drought, October 13, 2026

36%

of homes built before 1980

Soil under St. Charles Parish

Expansive clay (limits slab homes)44.0%
High water table (limits basements)63.2%
Septic fields very limited59.4%
Clay swell (LEP, by area)13.1%
High-swell land (LEP 6%+)44.9%
Urban land, not rated1.3%
Mapped soil260,800 acres
Soil seriesShare hereSeries nationally: high water table
Kenner19%n/a
Barbary10%n/a
Cancienne9%n/a
Schriever5%n/a
Allemands4%n/a
Fausse4%n/a
St. John the Baptist Parish: 61%Orleans Parish: 37%St. James Parish: 92%Lafourche Parish: 74%Jefferson Parish: 44%Ascension Parish: 91%Assumption Parish: 88%St. Tammany Parish: 67%St. Charles Parish St. John the BaptistOrleansSt. JamesLafourcheJeffersonAscensionAssumptionSt. TammanySt. Charles
St. Charles 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 LA089 (2025-08-28)

What the numbers mean here

Clay swell averages a linear extensibility of 13.1% by land area here, and 45% of the land reaches USDA's high class (6% or more). Clay like that swells when wet and shrinks when dry, under 44% of the mapped land.

Clay shrinks as it dries: 4.5% of the county is in drought on the latest map, and 44% of St. Charles Parish's mapped land has shrink-swell clay.

On 63% of St. Charles 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: 53.00 in, 11.09 in below the 1991-2020 average year of 64.09 in.

USDA rates 59% of the land very limited for septic absorption fields.

Drought

4.5% of the county is in drought (D1 or worse) on the October 13, 2026 map. Part of the county was in drought in 34 of the last 52 weeks; the most was 100% of its area, in 17 weeks, most recently on the May 19, 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 worse4.5%
D2 severe or worse0%
D3 extreme or worse0%
D4 exceptional0%

Flood losses since 2016

1,631 flood losses since 2016, $62.1 million paid. The worst year was 2021, with 748. Foundations of the buildings, where recorded: under 1% basements, 89% slabs, 4% crawl spaces, 7% elevated. Median water depth outside the building: 8 in.

YearFlood losses
201614
201716
201871
20197
2020402
2021748
20226
20232
2024223
202523
2026 to date119

Rain

Average year, 1991-202064.09 in
12 months to August 202653.00 in (-11.09)
202554.76 in (-9.33)
Wettest year since 18951991: 98.82 in
Driest year since 18951924: 38.92 in
Days with 1 inch or more, normal at NEW ORLEANS INTL AP (9 mi away)20.1

Homes

Housing units20,694
Median year built1986
Built before 198036%
Built 2000 or later24%
Owner-occupied82%
Median value, owner-occupied$263,700
Single-family detached77%

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. John the Baptist Parish, LA 18 mi 43% 61%
Orleans Parish, LA 27 mi 29% 37%
St. James Parish, LA 27 mi 68% 92%
Lafourche Parish, LA 29 mi 42% 74%
Jefferson Parish, LA 30 mi 27% 44%
Ascension Parish, LA 39 mi 46% 91%
Assumption Parish, LA 42 mi 68% 88%
St. Tammany Parish, LA 42 mi 4% 67%

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