Sinkhole risk in Roanoke city, VA: Sinkhole country
Sinkhole country
Soluble rock at or near the surface across much of the county.
- On soluble rock
- 98%
- At or near the surface
- 98%
- Buried under cover
- 0%
What to do about a house in Roanoke city
Get a sinkhole or geotechnical inspection before buying, building or adding weight to a foundation.
That works out to roughly 42 of Roanoke city's 43 square miles on soluble rock, 42 of them with the rock at or near the surface. With about 97,912 residents (2,303 per square mile), there is effectively nowhere in the county off the soluble rock, town or country. The figures come from 611 map points about 0.3 miles apart, so a pocket smaller than that can be missed or overstated.
Read next: the signs to look for and how an inspection works, and how these percentages are measured.
Counties around Roanoke city
The closest county with no soluble rock mapped is Franklin County, VA, about 20 miles south. 1 of the 6 closest counties land in the same band; the ground changes quickly around here.
- Salem city, VA 5 mi west · 100% at surface
- Roanoke County, VA 13 mi west · 33% at surface
- Craig County, VA 20 mi northwest · 34% at surface
- Franklin County, VA 20 mi south · under 1% at surface
- Botetourt County, VA 22 mi northeast · 49% at surface
- Bedford County, VA 24 mi east · 4% at surface
What Roanoke city is built on
The largest mapped soluble unit here is the Rome Formation (shale), Cambrian in age, covering about 73% of the county. Next is the Elbrook Formation at 17%.
Against the rest of Virginia
Roanoke city ranks 3 of 133 in Virginia for soluble rock at the surface, and sits above 99% of US counties on that measure.
- Lexington city 100%
- Salem city 100%
- Winchester city 90%
- Bristol city 89%
- Staunton city 89%