The Florida Geological Survey (FGS) was contracted by the Florida Division of Emergency Management (FDEM) to produce a map depicting the state’s vulnerability to sinkhole formation following a mass sinkhole event triggered by record rainfall from Tropical Storm Debby in June of 2012. The three-year project began with a pilot study in three northern Florida counties: Columbia, Hamilton and Suwannee. Prior to Tropical Storm Debby’s record rainfall, the state had been experiencing a multi-year drought leading to reduced groundwater levels within the Floridan aquifer system. The leading hypothesis is cavities that may have normally been water filled had developed unsaturated air space. The lack of hydrostatic buoyancy from the water meant the overburden (the sands and clays over the carbonate rocks) no longer had adequate support and collapsed when the record rainfall from TS Debby added increased hydrostatic loading and lubrication of overburden soils by rising groundwater levels weight over a very short time period.
Sinkholes are a geological hazard that place people’s property and even lives at risk. Vulnerability of an area to sinkhole formation is dependent upon both natural (geologic, hydrologic and meteorologic) and human (water pumping, terraforming, ground loading) factors. As Florida’s population continues to increase, the potential for encountering a sinkhole hazard increases.
Current sinkhole hazard maps that are available to FDEM are insufficient and poorly substantiated by available geologic data. The FDEM presently relies on two sources of activity: 1) a nonscientific qualitative self-assessment of risk reported by each county; and 2) publicly available and statistically biased subsidence incidence reports that are broadly generalized to the scale of entire counties without application of a scientifically defensible method.
For more information about sinkholes and subsidence, visit our Sinkhole FAQ page
The Florida Department of Environmental Protection is the state’s lead agency for environmental management and stewardship – protecting our air, water and land. The vision of the Florida Department of Environmental Protection is to create strong community partnerships, safeguard Florida’s natural resources and enhance its ecosystems.