Sinkhole risk in Franklin County, FL: Mostly deep or small

Mostly deep or small

Some soluble rock, mostly deeply buried or in a small share of the county.

On soluble rock: 41%
At or near the surface: 7%
Buried under cover: 34%

What this means before you buy

Sinkholes are uncommon here; watch for new depressions after heavy rain or leaking pipes.

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 226 of Franklin County's 545 square miles on soluble rock, 40 of them with the rock at or near the surface. With about 12,979 residents (24 per square mile), much of the land is open, and the mapped rock may sit far from where people actually live. The figures come from 517 map points about 1.0 miles apart, so a pocket smaller than that can be missed or overstated.

Worth reading for this county: what Florida insurers have to cover, and why the 34% under cover still counts.

Counties around Franklin County

The nearest county rated sinkhole country is Taylor County, FL, about 73 miles east. 2 of the 6 closest counties land in the same band; the ground changes quickly around here.

Gulf County, FL 30 mi northwest · 0% at surface
Wakulla County, FL 40 mi northeast · 45% at surface
Liberty County, FL 40 mi north · 15% at surface
Calhoun County, FL 54 mi northwest · 13% at surface
Bay County, FL 54 mi northwest · 0% at surface
Leon County, FL 63 mi northeast · 43% at surface

Which formation it is

The largest mapped soluble unit here is the Intracoastal Formation (limestone), Eocene in age, covering about 34% of the county. Next is the Intracoastal Formation at 7%.

Against the rest of Florida

Franklin County ranks 54 of 67 in Florida for soluble rock at the surface, and sits above 66% of US counties on that measure.