Sinkhole risk in Travis County, TX: Pockets of it

Pockets of it

Soluble rock at the surface or under thin cover in part of the county.

On soluble rock: 57%
At or near the surface: 57%
Buried under cover: 0%

What to do about a house in Travis County

Check the parcel against your state survey sinkhole map, and ask for an inspection if cracks, depressions or sticking doors show up.

That works out to roughly 566 of Travis County's 994 square miles on soluble rock, 566 of them with the rock at or near the surface. With about 1,363,767 residents (1,372 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 529 map points about 1.4 miles apart, so a pocket smaller than that can be missed or overstated.

Two things to read before deciding: the signs to look for and how an inspection works, and how these percentages are measured.

Counties around Travis County

The nearest county rated sinkhole country is Runnels County, TX, about 175 miles northwest. 3 of the 6 closest counties land in the same band; the ground changes quickly around here.

Hays County, TX 24 mi southwest · 88% at surface
Bastrop County, TX 25 mi southeast · 4% at surface
Caldwell County, TX 28 mi south · 8% at surface
Williamson County, TX 29 mi north · 46% at surface
Blanco County, TX 42 mi west · 90% at surface
Lee County, TX 43 mi east · 0% at surface

The rock underneath

The largest mapped soluble unit here is the Glen Rose Limestone (limestone), Early Cretaceous in age, covering about 32% of the county. Next is the Austin Chalk at 10%.

Against the rest of Texas

Travis County ranks 37 of 254 in Texas for soluble rock at the surface, and sits above 89% of US counties on that measure.