Sinkhole risk in Brown County, WI: 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: 99%
At or near the surface: under 1%
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 523 of Brown County's 530 square miles on soluble rock, 2 of them with the rock at or near the surface. With about 273,909 residents (517 per square mile), there is effectively nowhere in the county off the soluble rock, town or country. The figures come from 290 map points about 1.4 miles apart, so a pocket smaller than that can be missed or overstated.

Worth reading for this county: why the 98% under cover still counts, and how these percentages are measured.

Counties around Brown County

The nearest county rated sinkhole country is Oceana County, MI, about 97 miles southeast. 5 of the 6 closest counties land in the same band, so this is a regional pattern rather than a local quirk.

Outagamie County, WI 23 mi west · 0% at surface
Kewaunee County, WI 28 mi east · 0% at surface
Calumet County, WI 29 mi south · 0% at surface
Manitowoc County, WI 30 mi southeast · under 1% at surface
Oconto County, WI 38 mi north · under 1% at surface
Winnebago County, WI 43 mi southwest · under 1% at surface

What Brown County is built on

The largest mapped soluble unit here is the Sinnipee Group (dolostone (dolomite)), Ordovician in age, covering about 43% of the county. Next is the Silurian, undivided at 42%.

Against the rest of Wisconsin

Brown County ranks 21 of 72 in Wisconsin for soluble rock at the surface, and sits above 51% of US counties on that measure.