Sinkhole risk in Buchanan 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: 100%
At or near the surface: 0%
Buried under cover: 100%

The next step for one property

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

That works out to roughly 571 of Buchanan County's 571 square miles on soluble rock. With about 20,733 residents (36 per square mile), there is effectively nowhere in the county off the soluble rock, town or country. The figures come from 383 map points about 1.2 miles apart, so a pocket smaller than that can be missed or overstated.

Worth reading for this county: why the 100% under cover still counts, and how these percentages are measured.

Counties around Buchanan County

The nearest county rated sinkhole country is Clayton County, IA, about 37 miles northeast, 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.

Black Hawk County, IA 24 mi west · 0% at surface
Delaware County, IA 24 mi east · 5% at surface
Fayette County, IA 27 mi north · 19% at surface
Benton County, IA 28 mi southwest · 0% at surface
Linn County, IA 30 mi southeast · 0% at surface
Bremer County, IA 33 mi northwest · 0% at surface

The rock underneath

The largest mapped soluble unit here is the Cedar Valley Limestone (limestone), Middle Dovonian in age, covering about 62% of the county. Next is the Niagaran Series at 26%.

Against the rest of Iowa

Buchanan County ranks 22 of 99 in Iowa for soluble rock at the surface, and sits above 0% of US counties on that measure.