THE FAVORABILITY OF FLORIDA’S GEOLOGY TO SINKHOLE FORMATION

The Florida Division of Emergency Management (DEM) contracted the Florida Geological Survey (FGS) to map the favorability of the State’s geology to sinkhole formation. The request was made in response to a large outbreak of sinkholes across the State following Tropical Storm Debby in late June 2012. The project’s results are intended to bolster the State Hazard Mitigation Plan’s section on sinkhole hazards allowing for improved mitigation strategies. Previously, the state relied upon self-assessments by each county to judge their perceived risk sinkhole formation.

To create the map, the FGS used a modeling technique called Weights of Evidence (WofE) that involves the combination of diverse spatial data to describe and analyze interactions and generate predictive models from which a map of favorability can be produced. The project began with a one-year pilot study in Columbia, Hamilton, and Suwannee Counties, during which methodologies were developed in preparation to model the entire state. To train and validate the model, locations of sinkholes were required. Over two-and-a-half-years, field teams traversed the state investigating over 3,600 points of interest (potential sinkholes) and mapped 705 sinkholes. After evaluating fourteen different spatial data types, the three statistically strong spatial data layers were used to model the favorability of the State’s geology for sinkhole formation. The resulting map depicts four classes representing areas where the geology is least favorable to most favorable to sinkhole formation statewide. The map provides DEM an a scientifically defensible and effective tool to design mitigation strategies from.