Assessing the effects of rainfall, groundwater downward leakage, and groundwater head differences on the development of cover-collapse and cover-suffosion sinkholes in central Florida (USA).

Cover-collapse and cover-suffosion sinkholes are widely distributed in central Florida (USA) karst terrains and have been recognized as the primary geo-hazard threatening human lives and destroying infrastructure. Previous studies indicated that the development of cover-collapse and cover-suffosion sinkholes in central Florida might be related to hydrologic/hydrogeologic conditions such as rainfall, groundwater downward leakage and groundwater hydraulic head differences (groundwater level differences between the water tables in unconfined aquifer and the potentiometric levels in confined aquifer). Here, a case study in central Florida urban areas is conducted to quantify the effects of rainfall, groundwater downward leakage and groundwater head differences on the development of cover-collapse and cover-suffosion sinkholes in central Florida with a focus on the timing of their occurrences. Results indicate that heavy rainfall/storm(s) and rapid increase of head differences within a relatively short period of time are major factors affecting the timing of sinkhole occurrences, and the spatial variation of groundwater downward leakage rate can be used to generate sinkhole susceptibility zonation maps for serving as a useful indicator of the likelihood of sinkhole development at certain areas. Results caution that the groundwater pumping and mining dewatering rate should be setup properly and the starting time of groundwater pumping and/or mining dewatering should be selected carefully in central Florida, i.e., the activities should be put into abeyance after a heavy rainfall/storm(s) to reduce the probability of sinkhole occurrences.