Sinkhole risk in DeKalb County, AL: Pockets of it

Pockets of it

Soluble rock at the surface or under thin cover in part of the county.

On soluble rock: 21%
At or near the surface: 21%
Buried under cover: 0%

What to do about a house in DeKalb County

Check the parcel against your state survey sinkhole map, and ask for an inspection if cracks, depressions or sticking doors show up.

That works out to roughly 161 of DeKalb County's 777 square miles on soluble rock, 161 of them with the rock at or near the surface. With about 73,122 residents (94 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 507 map points about 1.2 miles apart, so a pocket smaller than that can be missed or overstated.

Counties around DeKalb County

The nearest county rated sinkhole country is Jackson County, AL, about 23 miles northwest, close enough that the same rock may run under the county line. 3 of the 6 closest counties land in the same band; the ground changes quickly around here.

Jackson County, AL 23 mi northwest · 60% at surface
Chattooga County, GA 26 mi east · 59% at surface
Cherokee County, AL 28 mi south · 57% at surface
Marshall County, AL 31 mi west · 29% at surface
Etowah County, AL 31 mi southwest · 46% at surface
Dade County, GA 32 mi northeast · 39% at surface

Which formation it is

The largest mapped soluble unit here is the Knox Group undifferentiated (dolostone (dolomite)), Ordovician-Cambrian in age, covering about 8% of the county. Next is the Monteagle Limestone at 4%.

Against the rest of Alabama

DeKalb County ranks 31 of 67 in Alabama for soluble rock at the surface, and sits above 75% of US counties on that measure.