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St. John the Baptist Parish, Louisiana
A shallow water table limits basements on 61% of St. John the Baptist Parish's mapped land, a higher share than 75% of US counties. Shrink-swell clay limits houses without basements on 43%.
83.2% of the county is in drought on the October 13, 2026 Drought Monitor map, up from 4% a week earlier. FEMA's flood data list 4,013 flood losses here since 2016, under 1% of them in buildings with basements. 41% of homes were built before 1980, against 50% nationally; the median home dates from 1984.
Data as of October 13, 2026 · sources
expansive clay: shrink-swell limits slab homes
high water table: limits basements
in drought, October 13, 2026
of homes built before 1980
Soil under St. John the Baptist Parish
| Expansive clay (limits slab homes) | 42.7% |
| High water table (limits basements) | 61.5% |
| Septic fields very limited | 60.8% |
| Clay swell (LEP, by area) | 13.6% |
| High-swell land (LEP 6%+) | 43.3% |
| Mapped soil | 220,500 acres |
| Soil series | Share here | Series nationally: high water table |
|---|---|---|
| Barbary | 27% | n/a |
| Cancienne | 8% | n/a |
| Maurepas | 6% | n/a |
| Schriever | 5% | n/a |
| Carville | 4% | n/a |
| Gramercy | 3% | n/a |
How we count · survey areas LA095 (2025-08-28)
What the numbers mean here
Clay swell averages a linear extensibility of 13.6% by land area here, and 43% of the land reaches USDA's high class (6% or more). Clay like that swells when wet and shrinks when dry, under 43% of the mapped land.
Clay shrinks as it dries: 83.2% of the county is in drought on the latest map, and 43% of St. John the Baptist Parish's mapped land has shrink-swell clay.
On 61% of St. John the Baptist 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: 55.26 in, 9.39 in below the 1991-2020 average year of 64.65 in.
USDA rates 61% of the land very limited for septic absorption fields.
Drought
83.2% of the county is in drought (D1 or worse) on the October 13, 2026 map. Part of the county was in drought in 31 of the last 52 weeks; the most was 100% of its area, in 12 weeks, most recently on the May 5, 2026 map.
| Category, October 13, 2026 | Share of county |
|---|---|
| D0 abnormally dry or worse | 100% |
| D1 moderate drought or worse | 83.2% |
| D2 severe or worse | 0% |
| D3 extreme or worse | 0% |
| D4 exceptional | 0% |
Flood losses since 2016
4,013 flood losses since 2016, $390.0 million paid. The worst year was 2021, with 3,653. Foundations of the buildings, where recorded: under 1% basements, 97% slabs, 2% crawl spaces, 1% elevated. Median water depth outside the building: 16 in.
| Year | Flood losses |
|---|---|
| 2016 | 15 |
| 2017 | 23 |
| 2018 | 12 |
| 2019 | 10 |
| 2020 | 43 |
| 2021 | 3,653 |
| 2022 | 16 |
| 2023 | 7 |
| 2024 | 226 |
| 2025 | 4 |
| 2026 to date | 4 |
Rain
| Average year, 1991-2020 | 64.65 in |
| 12 months to August 2026 | 55.26 in (-9.39) |
| 2025 | 52.62 in (-12.03) |
| Wettest year since 1895 | 1991: 90.83 in |
| Driest year since 1895 | 1924: 38.06 in |
| Days with 1 inch or more, normal at NEW ORLEANS INTL AP (18 mi away) | 20.1 |
Homes
| Housing units | 17,822 |
| Median year built | 1984 |
| Built before 1980 | 41% |
| Built 2000 or later | 24% |
| Owner-occupied | 78% |
| Median value, owner-occupied | $193,200 |
| Single-family detached | 81% |
What repairs cost
Published ranges from cost guides, not quotes. More sources, and where they disagree.
Nearby counties
| Place | Distance | Expansive clay | High water table |
|---|---|---|---|
| St. Charles Parish, LA | 18 mi | 44% | 63% |
| St. James Parish, LA | 20 mi | 68% | 92% |
| Livingston Parish, LA | 25 mi | 27% | 86% |
| Ascension Parish, LA | 26 mi | 46% | 91% |
| Tangipahoa Parish, LA | 33 mi | 2% | 73% |
| Orleans Parish, LA | 34 mi | 29% | 37% |
| St. Tammany Parish, LA | 37 mi | 4% | 67% |
| Assumption Parish, LA | 38 mi | 68% | 88% |
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