Sinkhole risk in Johnson County, NE: No soluble rock mapped

No soluble rock mapped

No soluble bedrock mapped.

On soluble rock: under 1%
At or near the surface: 0%
Buried under cover: under 1%

What to do about a house in Johnson County

No soluble bedrock is mapped here, so natural sinkholes are unlikely. Collapses from broken pipes or old mines are a separate risk.

That works out to roughly 1 of Johnson County's 376 square miles on soluble rock. With about 5,219 residents (14 per square mile), much of the land is open, and the mapped rock may sit far from where people actually live. The figures come from 400 map points about 1.0 miles apart, so a pocket smaller than that can be missed or overstated.

Two things to read before deciding: why gypsum and salt move faster than limestone, and how these percentages are measured.

Counties around Johnson County

The nearest county rated sinkhole country is Dickinson County, KS, about 116 miles southwest. 1 of the 6 closest counties land in the same band; the ground changes quickly around here.

Pawnee County, NE 18 mi south · 0% at surface
Otoe County, NE 18 mi northeast · 0% at surface
Nemaha County, NE 22 mi east · 0% at surface
Gage County, NE 24 mi southwest · 0% at surface
Richardson County, NE 34 mi southeast · 0% at surface
Lancaster County, NE 35 mi northwest · 0% at surface

What Johnson County is built on

The largest mapped soluble unit here is the Shawnee Group (limestone), Late Pennsylvanian- Virgilian in age, covering about under 1% of the county.

The county also lies over the Northern Anadarko Basin, a deep salt or gypsum basin. Deep beds rarely cause surface collapse on their own, but wells and mining into them have.

Against the rest of Nebraska

Johnson County ranks 64 of 93 in Nebraska for soluble rock at the surface, and sits above 0% of US counties on that measure.