SINKHOLES OF WEST-CENTRAL FLORIDA – THE HUMAN DIMENSION

In west-central Florida, where the Floridan aquifer is largely unconfined, the landscape is dominated by sinkholes, the aquifer is notably triply porous, and the environment is enriched by first-magnitude springs. Although the springs and triple porosity are being studied vigorously by state agencies, it is the occurrence of sinkholes that has caught the attention of the public and media. Human interaction with the landscape has increased as the population has grown and as sinkhole processes are exacerbated by human activities. Formed (and forming) in limestones typically mantled by young marine and eolian sands, the sinkholes are cover-collapse and cover-subsidence dolines formed as the sand falls or ravels into limestone voids. With the development of large urban and suburban populations in the region, particularly around active sinkhole regions of Orlando and Tampa, there have been unnaturally large variations in water levels, and these have impacted ground stability. Sinkhole damage to homes is common and distinctly regional. Insurance issues associated with property damage due to subtle subsidence are highly controversial and have led to a rash of lawsuits and the development of law firms specializing in sinkhole claims. Sinkhole mapping is problematic in the urbanized areas. Many sinkholes have never been mapped because they have been filled as the sprawl has expanded. Moreover, unknown numbers of sinkholes are below the resolution of standard topographic maps and reveal themselves only because of cracks and unfitting doors in buildings affected by subsiding ground. Because of the multiple possible causes of the subsidence, insurance and, hence, legal issues have spawned a geological industry specializing in post-subsidence site investigations. Although the cause of subsidence at many sites is clear cut, there are many for which professional geologists representing insurance companies disagree with professional geologists representing homeowners.