Sinkhole risk in Multnomah County, OR: Not karst, but voids possible

Not karst, but voids possible

No soluble bedrock; some pseudokarst (piping or lava-tube ground).

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

The next step for one property

Not true karst, but soil piping or lava tubes can still open voids - mention it to an inspector.

Across 431 square miles, under one square mile of Multnomah County maps onto soluble rock. With about 795,897 residents (1,847 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 428 map points about 1.0 miles apart, so a pocket smaller than that can be missed or overstated.

Counties around Multnomah County

The nearest county rated sinkhole country is Emery County, UT, about 748 miles southeast. 4 of the 6 closest counties land in the same band, so this is a regional pattern rather than a local quirk.

Clark County, WA 16 mi north · 0% at surface
Clackamas County, OR 29 mi south · 0% at surface
Washington County, OR 33 mi west · 0% at surface
Hood River County, OR 37 mi east · 0% at surface
Skamania County, WA 40 mi northeast · 0% at surface
Columbia County, OR 42 mi northwest · 0% at surface

Against the rest of Oregon

Multnomah County ranks 30 of 36 in Oregon for soluble rock at the surface, and sits above 0% of US counties on that measure.