Crawl space moisture in Louisiana

Most of Louisiana sits on soil that holds water: 54 of its 64 counties score high or elevated, led by Cameron Parish at 87. In much of the state a vented crawl space over bare ground is working against the soil it was built on.

1Wettest county Cameron Parish
2High or elevated 54 of 64
3Median score 62
4Driest county Lincoln Parish

Soil moisture score (0–100) for the 15 highest of 64 counties in Louisiana, bars to scale. Score from USDA NRCS drainage class, hydrologic group, water-table depth and flooding; see methodology.

Louisiana: counties by soil moisture tier, columns to scale.

Louisiana's soil, taken as a whole

Across the 30,561,543 acres mapped in these 64 counties, 64% of soil with a drainage class is somewhat poorly, poorly or very poorly drained, and 74% of acres report a seasonal water table within about two metres. That is a wet state by any measure; a third or more of its land holds water near the surface for part of the year. 63 of the 64 counties have mapped soils subject to occasional or frequent flooding.

Drainage class	Share of mapped acres
Excessively drained	0.2%
Somewhat excessively drained	0.6%
Well drained	18%
Moderately well drained	17.2%
Somewhat poorly drained	21.1%
Poorly drained	27.4%
Very poorly drained	15.4%

Radon. By EPA zone, 0 Louisiana counties here are zone 1 (highest potential), 0 zone 2 and 63 zone 3; 1 are not in the EPA table. EPA says to test regardless of zone; a sealed crawl space is the cheapest moment to add radon venting if a test calls for it.

Every Louisiana county

Sorted wettest first. High and elevated counties link to their own page with the full soil breakdown.

Cameron Parish 87 St. Mary Parish 85 Terrebonne Parish 85 Assumption Parish 84 St. James Parish 84 Lafourche Parish 82 Iberville Parish 81 Concordia Parish 80 St. Bernard Parish 80 St. Charles Parish 80 St. John the Baptist Parish 80 Calcasieu Parish 79 Madison Parish 78 Vermilion Parish 78 Iberia Parish 77 Jefferson Davis Parish 77 St. Martin Parish 77 Tensas Parish 77 Ascension Parish 76 Plaquemines Parish 75 Livingston Parish 74 East Carroll Parish 73 Acadia Parish 72 Jefferson Parish 72 Orleans Parish 71 Catahoula Parish 66 Franklin Parish 66 West Baton Rouge Parish 66 St. Landry Parish 65 Allen Parish 64 Evangeline Parish 64 East Baton Rouge Parish 62 Avoyelles Parish 61 Richland Parish 60 West Carroll Parish 60 Pointe Coupee Parish 59 Caldwell Parish 58 St. Tammany Parish 58 Morehouse Parish 57 Lafayette Parish 56 Bossier Parish 54 Winn Parish 54 Beauregard Parish 52 Natchitoches Parish 49 Tangipahoa Parish 49 Ouachita Parish 47 Rapides Parish 45 Red River Parish 44 Webster Parish 44 Bienville Parish 43 Caddo Parish 43 LaSalle Parish 43 Vernon Parish 43 Sabine Parish 42 East Feliciana Parish 39 De Soto Parish 37 Jackson Parish 37 St. Helena Parish 37 Grant Parish 36 Union Parish 34 Washington Parish 33 West Feliciana Parish 30 Claiborne Parish 24 Lincoln Parish 23

What drives the Louisiana numbers

The wettest county, Cameron Parish, is 80% very poorly drained by dominant condition, with a seasonal water table averaging 0.3 ft below grade across the 75% of acres that report one, and sits in EPA radon zone 3. The driest, Lincoln Parish, is 60% well drained. 35 Louisiana counties reach the high tier, where poorly drained soils, group D clays and a shallow water table occur together.

The score is a guide to the soil, not to a house: a well-graded lot with working gutters in a high county can have a dry crawl space, and a bad downspout can flood one in a low county. The R408 calculator sizes venting or encapsulation for any footprint.

Sources: USDA NRCS SSURGO via Soil Data Access (muaggatt: drclassdcd, hydgrpdcd, flodfreqdcd, pondfreqprs, wtdepannmin), acreage-weighted; EPA Map of Radon Zones, county table (June 2024 JSON). Checked 2026-10-23.