Sinkhole risk in Louisa County, IA: Mostly deep or small

Mostly deep or small

Some soluble rock, mostly deeply buried or in a small share of the county.

On soluble rock: 98%
At or near the surface: 0%
Buried under cover: 98%

What this means before you buy

Sinkholes are uncommon here; watch for new depressions after heavy rain or leaking pipes.

That works out to roughly 395 of Louisa County's 402 square miles on soluble rock. With about 10,630 residents (26 per square mile), there is effectively nowhere in the county off the soluble rock, town or country. The figures come from 245 map points about 1.3 miles apart, so a pocket smaller than that can be missed or overstated.

Counties around Louisa County

The nearest county rated sinkhole country is Jo Daviess County, IL, about 96 miles northeast. 6 of the 6 closest counties land in the same band, so this is a regional pattern rather than a local quirk.

Muscatine County, IA 20 mi north · 0% at surface
Des Moines County, IA 21 mi south · 3% at surface
Henry County, IA 22 mi southwest · 0% at surface
Washington County, IA 25 mi west · 0% at surface
Mercer County, IL 27 mi east · 0% at surface
Henderson County, IL 32 mi southeast · 0% at surface

What Louisa County is built on

The largest mapped soluble unit here is the Yellow Spring Group (shale), Late Devonian in age, covering about 32% of the county. Next is the Cedar Valley Limestone at 28%.

Against the rest of Iowa

Louisa County ranks 60 of 99 in Iowa for soluble rock at the surface, and sits above 0% of US counties on that measure.