Sinkhole Risk in Hillsborough County
How sinkhole risk is actually measured in Hillsborough County — the Florida Geological Survey favorability map vs. reported subsidence incidents, what each one tells you, and why the zone alone is not a verdict.
Updated July 12, 2026 · 7 min read
Quick answer
The two datasets, and why the difference matters
Almost every “sinkhole map” you’ll find online is the favorability raster, and almost everyone misreads it. It is a model of the underlying karst geology — how close the limestone is to the surface, how thick the overburden is — not a record of anything that has happened. It answers “is this the kind of ground where sinkholes form?” In much of Hillsborough County the answer is yes, which is exactly why the map alone is nearly useless for picking a property.
- Favorability zone (geology). A statewide raster from the Florida Geological Survey. REI Radar buckets it into low / moderate / high at each parcel’s centroid. Roughly 61% of Hillsborough County falls into “favorable or worse” — so this is a filter, not a verdict.
- Subsidence incident reports (history). Individual, geolocated reports of ground collapse or depression submitted to the FGS, with fields for whether property damage occurred, whether it was verified as a true sinkhole, and whether it was repaired. This is the signal that actually moves a property’s risk.
Which one actually moves a property
Because the favorability zone covers so much of the county, REI Radar treats it as a filter, not a risk rating. What genuinely changes a property’s profile is reported subsidence history near the parcel — and, above all, whether that history involved property damage and whether it was ever repaired. An unrepaired incident with recorded damage is a different property from one sitting in a broad geological band, and REI Radar grades them accordingly.
That distinction is the whole game here, and it’s where most “sinkhole map” tools stop — they show you the geology and leave you to figure out the rest.
Reading the signal honestly
Two limits worth internalizing before you build a strategy on this data:
- The incident database is self-reported. Someone had to call it in. An absence of reports near a parcel does not mean an absence of risk — it may just mean nobody filed. Treat it as a positive signal when present, not an all-clear when missing.
- Proximity is not the property. An incident within the radius means something happened nearby. It may have been on the neighbor’s lot, and it may have been a small depression rather than a catastrophic collapse. It’s a prompt to pull the actual report, not a conclusion.
Why investors care
Sinkhole exposure hits a Florida property in three places at once: insurability (carriers decline or surcharge), financing (no insurance, no conventional loan), and resale (a permanent, recorded stigma). That triple hit is why these homes trade at a discount — and why owners of a home with a sinkhole history are often genuinely motivated to sell, sometimes far below what the repair actually costs.
That gap is the opportunity, but only if you can price the repair and the insurance. Read Buying a House With a Sinkhole in Florida for the underwriting side, and Florida Sinkhole Disclosure Law for what the seller is legally required to tell you.
Where to check it yourself
- Florida Geological Survey (FDEP) — subsidence incident reports and the favorability map.
- Hillsborough County Clerk, Official Records — recorded sinkhole reports run with the title (see the disclosure guide).
- The seller’s insurer — a paid sinkhole claim leaves a paper trail; ask for it.
This guide is general information for real estate investors and property owners, not legal, tax, or financial advice. Court procedures, fees, and statutes change — verify current details with the Hillsborough County Clerk of Circuit Court or a licensed Florida attorney before acting.
Frequently asked questions
Is Hillsborough County in a sinkhole zone?
Largely, yes — Hillsborough sits at the edge of Florida’s "sinkhole alley," the Tampa Bay belt with the state’s heaviest reported subsidence activity. But roughly 61% of the county falls into the "favorable or worse" geology band on the Florida Geological Survey map, which is why the zone alone tells you almost nothing about a specific house. Reported incident history is the signal that matters.
What is the difference between a sinkhole favorability map and a subsidence incident report?
The favorability map models the underlying karst geology — where sinkholes could form based on limestone depth and overburden. It is not a record of anything that has happened. Subsidence incident reports are individual, geolocated reports of actual ground collapse submitted to the Florida Geological Survey, with fields for property damage, verification, and repair status. Only the second one says something about a specific property.
How do I check if a property has a sinkhole history?
Check three places: the Florida Geological Survey subsidence incident reports for the surrounding area, the Hillsborough County Clerk’s Official Records (a paid sinkhole claim is recorded and runs with the property), and the seller’s own insurance claim file. REI Radar automates the first by mapping every county parcel against both FGS datasets during its weekly ingest.
Does no sinkhole report mean a property is safe?
No. The subsidence incident database is self-reported — someone had to call it in. An absence of reports near a parcel may simply mean nobody filed one. Treat a reported incident as a strong positive signal when it is present, but never treat its absence as an all-clear.