Sinkhole risk in DeKalb County, TN: Sinkhole country

Sinkhole country

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

On soluble rock: 61%
At or near the surface: 61%
Buried under cover: 0%

What this means before you buy

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

That works out to roughly 186 of DeKalb County's 304 square miles on soluble rock, 186 of them with the rock at or near the surface. With about 21,747 residents (71 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 264 map points about 1.1 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 DeKalb County

The closest county with no soluble rock mapped is Morgan County, TN, about 68 miles east. 6 of the 6 closest counties land in the same band, so this is a regional pattern rather than a local quirk.

Cannon County, TN 18 mi southwest · 63% at surface
Smith County, TN 21 mi north · 87% at surface
Warren County, TN 21 mi south · 81% at surface
White County, TN 21 mi east · 74% at surface
Putnam County, TN 22 mi northeast · 60% at surface
Jackson County, TN 27 mi north · 58% at surface

Which formation it is

The largest mapped soluble unit here is the Ordovician [units] including Richmond Group (which includes Mannie Shale, Fernvale Limestone, Sequatchie Formation, and Arnheim Formation), the Maysville Group (which includes Leipers Formation), the Eden Group (which includes Inman Formation), and (shale), Ordovician in age, covering about 27% of the county. Next is the St. Louis Limestone and Warsaw Limestone at 14%.

Against the rest of Tennessee

DeKalb County ranks 42 of 95 in Tennessee for soluble rock at the surface, and sits above 90% of US counties on that measure.