Sinkhole risk in Indian River County, FL: Sinkhole country

Sinkhole country

Soluble rock at or near the surface across much of the county.

On soluble rock: 92%
At or near the surface: 56%
Buried under cover: 36%

What to do about a house in Indian River County

Get a sinkhole or geotechnical inspection before buying, building or adding weight to a foundation.

Standard Florida homeowners policies cover only catastrophic ground cover collapse; full sinkhole coverage is a separately priced option insurers must offer.

That works out to roughly 461 of Indian River County's 503 square miles on soluble rock, 282 of them with the rock at or near the surface. With about 172,139 residents (343 per square mile), there is effectively nowhere in the county off the soluble rock, town or country. The figures come from 306 map points about 1.3 miles apart, so a pocket smaller than that can be missed or overstated.

Counties around Indian River County

The closest county with no soluble rock mapped is Gulf County, FL, about 321 miles northwest. 2 of the 6 closest counties land in the same band; the ground changes quickly around here.

St. Lucie County, FL 24 mi south · 83% at surface
Okeechobee County, FL 29 mi southwest · 38% at surface
Brevard County, FL 42 mi north · 40% at surface
Osceola County, FL 42 mi northwest · 3% at surface
Martin County, FL 44 mi south · 87% at surface
Highlands County, FL 53 mi southwest · 7% at surface

The rock underneath

The largest mapped soluble unit here is the Shelly sediments of Plio-Pleistocene age (beach sand), Holocene in age, covering about 36% of the county. Next is the Anastasia Formation at 35%.

The county also lies over the Floridan shelf, 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 Florida

Indian River County ranks 21 of 67 in Florida for soluble rock at the surface, and sits above 89% of US counties on that measure.