Sinkhole risk in Johnson County, KS: Sinkhole country
Sinkhole country
Soluble rock at or near the surface across much of the county.
- On soluble rock
- 77%
- At or near the surface
- 67%
- Buried under cover
- 11%
What to do about a house in Johnson County
Get a sinkhole or geotechnical inspection before buying, building or adding weight to a foundation.
That works out to roughly 367 of Johnson County's 474 square miles on soluble rock, 316 of them with the rock at or near the surface. With about 632,276 residents (1,335 per square mile), most of the county is built up, so a mapped unit is likely to sit under somebody's street. The figures come from 371 map points about 1.1 miles apart, so a pocket smaller than that can be missed or overstated.
Read next: why the 11% under cover still counts, and the signs to look for and how an inspection works.
Counties around Johnson County
The closest county with no soluble rock mapped is Nemaha County, NE, about 117 miles northwest. 3 of the 6 closest counties land in the same band; the ground changes quickly around here.
- Wyandotte County, KS 16 mi north · 7% at surface
- Miami County, KS 22 mi south · 87% at surface
- Leavenworth County, KS 24 mi northwest · 0% at surface
- Douglas County, KS 25 mi west · 23% at surface
- Jackson County, MO 27 mi east · 71% at surface
- Cass County, MO 30 mi southeast · 72% at surface
Which formation it is
The largest mapped soluble unit here is the Lansing Group (shale), Middle Pennsylvanian- Missourian in age, covering about 40% of the county. Next is the Kansas City Group at 37%.
Against the rest of Kansas
Johnson County ranks 17 of 105 in Kansas for soluble rock at the surface, and sits above 92% of US counties on that measure.
- Butler County 93%
- Morris County 91%
- Allen County 90%
- Miami County 87%
- Chase County 87%