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Buying land in Karnes County, Texas: what to check

Karnes County covers 748 square miles of land and 6 of water in Texas, with about 15,137 residents in 2024 (up 2.5% since 2020). The 2020 Census counted 100% of its land as rural and 0% of residents as living in urban areas. Farms operate 82% of the county's land. Below: how much of Karnes County floods, what its soils allow, what farmland is worth and how often it's in drought, from free public data with every source linked.

Check a location in Karnes CountySee a sample report

Karnes County at a glance

In the 100-year floodplain

8.2%

Above the state's county median (2.4%)

FEMA National Risk Index

Hydric (wetland-type) soils

under 1%

About the state's county median (under 1%)

USDA NRCS Web Soil Survey (SSURGO)

Soils very limited for septic

85%

USDA NRCS Web Soil Survey (SSURGO)

Farm land value, 2022

$2,951/acre

Above the state's county median ($2,782)

USDA NASS, 2022 Census of Agriculture

Weeks in severe drought

40%

Share of weekly maps, 2021–2026

U.S. Drought Monitor county statistics

Land classed rural

100%

Census 2020 Census urban and rural classification

What to check before buying land in Karnes County

Ordered by what Karnes County's numbers point to. Every parcel differs, so treat this as where to look first.

  1. 1.Budget for a perc test and maybe an engineered septic

    USDA rates 85% of Karnes County's mapped soils "very limited" for conventional septic absorption fields and 0% "not limited".

    Without city sewer you need a septic permit from the county or state health department. Make the offer contingent on a passing soil or perc test; mound and aerobic systems can cost several times a conventional one.

    Guide: Perc tests and septic systems

  2. 2.Prove the water supply before you buy

    At least half of Karnes County was in severe drought (D2) or worse in 40% of the 262 weekly U.S. Drought Monitor maps from 2021 to 2026. Texas allocates water by permit or water right, so a well or pond isn't automatic.

    Ask whether the land has a public water connection, an existing well (and its log and yield), or neighbors' well depths from the state well database. For a new well, check permits and typical depth with the state agency first.

    Guide: Wells, public water and water rights

  3. 3.Confirm the flood zone at your exact spot

    8.2% of the county's area is in the 1%-annual-chance (100-year) floodplain FEMA's National Risk Index uses for inland flooding; 7.3% of its mapped soils flood occasionally or frequently.

    Even where little of the county floods, creeks and low spots do. Check the FEMA zone at the building site and the driveway route.

    Guide: Flood zones before buying land

  4. 4.Confirm legal road access and power

    The 2020 Census classified 100% of Karnes County's land area as rural.

    Rural tracts are often sold without recorded access or a power line nearby. Get the title company to confirm a recorded easement or public road frontage, and ask the electric co-op what a line extension costs.

    Guide: Road access and landlocked land

  5. 5.Check the soils if you plan to farm, graze or garden

    Farm real estate in Karnes County averaged $2,951 an acre including buildings in the 2022 Census of Agriculture, and 65% of its mapped soils are prime or of statewide importance.

    Compare the asking price with recent sales of similar tracts, not the county average, which mixes cropland, pasture, timber and homesites. If an ag tax valuation applies, ask what the rollback taxes would be if you change the use.

    Guide: Land due diligence checklist

  6. 6.Check wildfire exposure and insurance

    FEMA rates Karnes County's wildfire risk very low, and 17% of the county's area is in the wildfire exposure zone the National Risk Index uses.

    Ask an insurer for a quote early; some carriers won't write new policies in high-hazard areas. Check access for fire trucks, nearby fire stations and the vegetation around the building site.

    Guide: Wildfire risk for rural land

Flood zones, wetlands and water in Karnes County

Area in the 1%-annual-chance (100-year) floodplain
8.2%, 63rd highest of 254 in Texas FEMA National Risk Index
Mapped soils that flood occasionally or frequently
7.3% USDA NRCS Web Soil Survey (SSURGO)
Hydric soils (a federal wetland indicator)
under 1% USDA NRCS Web Soil Survey (SSURGO)
Poorly or very poorly drained soils
0% USDA NRCS Web Soil Survey (SSURGO)
Surface water (lakes, rivers, reservoirs)
6 sq mi Census 2024 Gazetteer Files
Drought on 2026-10-27
100% moderate or worse, 100% severe or worse U.S. Drought Monitor county statistics

The floodplain share is the area FEMA's National Risk Index counts as exposed to inland flooding, mostly mapped 100-year flood zones. It says how common flood-prone land is in Karnes County, not whether a given parcel floods. For that, look up the zone at your exact point on the FEMA Flood Map Service Center or run the free check.

Soils and terrain

Prime farmland
63% USDA NRCS Web Soil Survey (SSURGO)
Prime only if drained, irrigated or protected
8% USDA NRCS Web Soil Survey (SSURGO)
Farmland of statewide importance
2.7% USDA NRCS Web Soil Survey (SSURGO)
Average slope over 15%
under 1% USDA NRCS Web Soil Survey (SSURGO)
Very limited for septic absorption fields
85% USDA NRCS Web Soil Survey (SSURGO)
Not limited for septic absorption fields
0% USDA NRCS Web Soil Survey (SSURGO)

Shares of Karnes County's soil-surveyed land (about 479,620 acres, open water excluded), using each map unit's dominant condition in USDA's SSURGO soil survey. Soils change within a few hundred feet, so the soil at your building site is what matters.

Farms and land use

Farms (2022)
958 USDA NASS, 2022 Census of Agriculture
Share of the county's land in farms
82% USDA NASS, 2022 Census of Agriculture
Average farm size
407 acres (median 126) USDA NASS, 2022 Census of Agriculture
Average value of land and buildings
$2,951 per acre, 123rd highest of 254 in Texas USDA NASS, 2022 Census of Agriculture
Cropland
68,844 acres USDA NASS, 2022 Census of Agriculture
Pasture and rangeland
322,572 acres USDA NASS, 2022 Census of Agriculture
Woodland on farms
43,262 acres USDA NASS, 2022 Census of Agriculture
Irrigated land
1,891 acres USDA NASS, 2022 Census of Agriculture

Natural hazard ratings

FEMA's National Risk Index rates each hazard for Karnes County relative to every other U.S. county. Overall risk: Relatively Low.

  • DroughtRelatively Moderate
  • HailRelatively Moderate
  • HurricaneRelatively Moderate
  • Heat waveRelatively Low
  • River and inland floodingRelatively Low
  • LightningRelatively Low
  • Strong windRelatively Low
  • TornadoRelatively Low
  • Winter weatherRelatively Low
  • EarthquakeVery Low
  • LandslideVery Low
  • WildfireVery Low

FEMA National Risk Index, December 2025

Questions about buying land in Karnes County

How much of Karnes County, TX is in a flood zone?

About 8.2% of Karnes County's area is in the 1%-annual-chance (100-year) floodplain used by FEMA's National Risk Index (December 2025), 63rd highest of 254 counties in Texas. Whether a given parcel is in a flood zone depends on its exact location, so check the FEMA map at your pin.

How much does land cost per acre in Karnes County?

The 2022 Census of Agriculture put the average value of farm land and buildings in Karnes County at $2,951 an acre, 123rd highest of 254 counties in Texas (the median Texas county was $2,782). It's a self-reported average across farms, so small homesites and recreational tracts often sell for more per acre.

Will a septic system work on land in Karnes County?

Often, but test first. USDA soil surveys rate 85% of Karnes County's mapped soils very limited for conventional septic absorption fields, usually because of wetness, slow permeability, shallow rock or flooding. A perc or soil test on the parcel decides what system the health department will permit.

Is there good farmland in Karnes County?

63% of Karnes County's mapped soils are prime farmland, 8% are prime only if drained, irrigated or protected from flooding, and 2.7% are farmland of statewide importance (USDA SSURGO). The 2022 Census of Agriculture counted 958 farms averaging 407 acres.

How often is Karnes County in drought?

Since 2021, at least half of the county was in severe drought or worse in 40% of weekly U.S. Drought Monitor maps, and in extreme drought in 21%. On 2026-10-27, 100% of the county was in moderate drought or worse.

Can I check a specific property in Karnes County?

Yes. Enter the address or drop a pin anywhere in Karnes County on the free check. It shows which checks return data at that exact point, and the full report costs $29: flood zone, slope, soils, wetlands, roads, power lines, wildfire and more, each with its source. It is a screen of public maps, not a survey, title search or perc test.

Check the parcel, not just the county

County numbers tell you what to look for. The free check looks at your exact point in Karnes County: flood zone, slope, soils, wetlands, roads, power and more. The full report is $29.

Check a location in Karnes County

What these numbers can't tell you

  • County shares describe Karnes County as a whole; a parcel can be entirely in or out of a flood zone, wetland or poor soil.
  • It doesn't look at the whole parcel, its boundaries, title, easements, zoning or permits.
  • It isn't a survey, appraisal, elevation certificate, soil or perc test, or Phase I environmental site assessment.
  • It can't see local distribution power lines, driveways, legal access, wells or mineral rights.
  • Maps lag behind the ground, and distances are straight-line, not driving distance.

Sources and vintages

Summarized per county by our build script on 2026-10-31. County figures cover the whole county; checks on the report are at your point.