Sinkhole risk in Houston County, AL: Sinkhole country

Sinkhole country

Soluble rock at or near the surface across much of the county.

On soluble rock: 86%
At or near the surface: 84%
Buried under cover: 2%

What to do about a house in Houston County

Get a sinkhole or geotechnical inspection before buying, building or adding weight to a foundation.

That works out to roughly 497 of Houston County's 580 square miles on soluble rock, 488 of them with the rock at or near the surface. With about 109,366 residents (189 per square mile), homes are spread across towns and farmland, and a mapped unit may or may not reach the developed parts. The figures come from 258 map points about 1.5 miles apart, so a pocket smaller than that can be missed or overstated.

Two things to read before deciding: the signs to look for and how an inspection works, and how these percentages are measured.

Counties around Houston County

The closest county with no soluble rock mapped is Quitman County, GA, about 52 miles north. 4 of the 6 closest counties land in the same band, so this is a regional pattern rather than a local quirk.

Henry County, AL 25 mi north · 20% at surface
Early County, GA 26 mi northeast · 81% at surface
Jackson County, FL 26 mi south · 87% at surface
Dale County, AL 26 mi northwest · 7% at surface
Seminole County, GA 30 mi southeast · 86% at surface
Geneva County, AL 31 mi west · 51% at surface

The rock underneath

The largest mapped soluble unit here is the Claiborne/Jackson Group; Residuum (residuum), Eocene-Oligocene in age, covering about 84% of the county. Next is the Jackson Group undifferentiated at 2%.

Against the rest of Alabama

Houston County ranks 1 of 67 in Alabama for soluble rock at the surface, and sits above 95% of US counties on that measure.