Soil survey area

Big Bend National Park, Texas

Survey Area TX621• Texas
The short version

The most common soil here is Corazones, on about 15% of the land: a very gravelly sandy loam, gritty and crumbly. Blackgap and Chilicotal come next.

About 80% of the land drains well.

USDA rates 70% of the land very limited for a standard septic drain field, and 68% very limited for homes with basements. That means extra cost or special design, not that it can't be done.

Worth knowing: 3% of the land floods occasionally or more, and bedrock lies within 40 inches under 58% of it.

Soils change over short distances, so look up an address below for the soil at that exact spot and the reasons behind each rating.

The ground underfoot

The soils you're most likely standing on

The biggest named soils in Big Bend National Park, Texas, each drawn five feet deep from its official USDA description, in its recorded colors.

Corazones
15% of the area
Very gravelly sandy loam topsoil · well drained
Gritty and crumbly. Drains fast and warms early in spring.
Aridisols
Blackgap
7% of the area
Very cobbly silt loam topsoil · well drained
Smooth, like flour. Fertile and holds water well.
Aridisols
Chilicotal
5% of the area
Very gravelly fine sandy loam topsoil · well drained
Gritty and crumbly. Drains fast and warms early in spring.
Aridisols
Geefour
4% of the area
Very gravelly silty clay topsoil · well drained
Smooth and very sticky when wet. Slow to drain.
Entisols
Lingua
4% of the area
Very gravelly sandy clay loam topsoil · well drained
Gritty but holds together. Drains moderately.
Entisols
Solis
4% of the area
Fine sandy loam topsoil · well drained
Gritty and crumbly. Drains fast and warms early in spring.
Entisols

Dots mark gravel; white flecks mark lime. Shares are by acres across the survey area, and each mapped patch usually mixes several of these soils.

The biggest mapped areas

The dominant drainage class is Well drained and the dominant hydrologic group is D (very slow infiltration, high runoff). The most common soil order is Aridisols — dry-climate soils with limited organic matter and often calcium carbonate accumulation. This report summarizes the major soil map units across the survey area to help you understand what to expect when buying, building, or gardening in Big Bend National Park, Texas. Search your address to find the exact soil composition, drainage, and series details at your specific location.

Soil Map UnitAcresDrainageHydro GroupDwellingsSeptic
Corazones very gravelly sandy loam, 1 to 8 percent slopes 92K Well drainedANot limitedNot limited
Lingua-Rock outcrop complex, 20 to 60 percent slopes 76K DVery limitedVery limited
Solis-Rock outcrop complex, 1 to 20 percent slopes 53K DVery limitedVery limited
Corazones very gravelly sandy loam, 1 to 30 percent slopes 48K Well drainedASomewhat limitedSomewhat limited
Strawhouse-Stillwell complex, 1 to 8 percent slopes 45K Well drainedDVery limitedVery limited
Blackgap-Rock outcrop complex, 20 to 70 percent slopes 41K Well drainedDVery limitedVery limited
Chilicotal very gravelly fine sandy loam, 1 to 8 percent slopes 38K Well drainedBNot limitedSomewhat limited
Leyva-Rock outcrop complex, 10 to 30 percent slopes 37K Well drainedDVery limitedVery limited
Ninepoint clay loam, 0 to 3 percent slopes 32K Well drainedCSomewhat limitedVery limited
Geefour silty clay, 3 to 20 percent slopes 28K Well drainedDVery limitedVery limited
Blackgap-Rock outcrop complex, 10 to 30 percent slopes 27K Well drainedDVery limitedVery limited
Geefour silty clay, 10 to 45 percent slopes 21K Well drainedDVery limitedVery limited
Mariscal-Terlingua complex, 10 to 30 percent slopes 21K Well drainedDVery limitedVery limited
Bissett-Rock outcrop complex, 20 to 70 percent slopes 20K Well drainedDVery limitedVery limited
Blackgap-Rock outcrop complex, 1 to 16 percent slopes 20K Well drainedDVery limitedVery limited
Chilicotal-Paisano association, 5 to 30 percent slopes 19K Well drainedBSomewhat limitedSomewhat limited
Mariscal-Rock outcrop complex, 5 to 30 percent slopes 18K DVery limitedVery limited
Chillon very gravelly fine sandy loam, 1 to 3 percent slopes, rarely flooded 18K Well drainedBVery limitedSomewhat limited
Solis-Rock outcrop complex, 20 to 60 percent slopes 17K Well drainedDVery limitedVery limited
Bissett-Rock outcrop complex, 10 to 30 percent slopes 16K Well drainedDVery limitedVery limited

Soil Orders in This Area

The USDA classifies every soil into one of 12 soil orders. Here are the dominant orders found in this survey area.

Aridisols
Dry-climate soils with low organic matter. Often have caliche layers that make excavation difficult. Low shrink-swell is good for foundations.
Entisols
Young soils with little development — found on floodplains, dunes, and steep slopes. Properties vary widely by setting.
Mollisols
Fertile grassland soils with thick, dark topsoil. Among the best for agriculture, building, and gardening.

What This Means

Building & Foundations

About 68% of soils are rated "very limited" for dwellings with basements. Specific challenges include shallow bedrock, steep slopes, flood-prone areas. A geotechnical assessment is recommended before building.

Septic Systems

About 70% of soils are rated "very limited" for septic absorption fields. Despite good drainage overall, limitations may stem from shallow bedrock, steep slopes, or seasonal conditions. Engineered or alternative systems are frequently required. Always get a professional perc test before purchasing land that needs septic.

Gardening & Agriculture

Well-drained soils on sloped terrain — good for most plants but watch for erosion. Terracing, contour planting, and mulching help retain moisture and topsoil. Drip irrigation is more effective than sprinklers on slopes.

Look Up a Specific Address

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