The process by which sinkholes form in nature is complicated by an additionally important factor: the anthropogenic effect, or urban development in karst areas. As demand for undeveloped land increases, less desirable properties such as karst-prone areas become a target for human construction or development (Ripp and Baker, 1997). Direct contact with an unstable subsurface is the obvious drawback, but not the only geohazard. Other problems related to development of these areas include sources for non-natural sinkhole development. These issues are de-watering, alteration of surface drainage patterns, increase or redistribution of overburden and blasting for quarries and highways (Fig. 14). In Florida, de-watering or aquifer draw down from well field pumping is a major factor (USGS WRI 85-4126), since the potable water supply for metropolitan areas are pumped from aquifers nearby. The magnitude of water removed from the subsurface creates draw down in the aquifer which removes the supporting pressure needed to maintain integrity of the overlying material and land surface. Figure 14 shows typical scenarios where high rates of groundwater withdrawal increase the likelihood of surface collapse. White (1988) estimates that since 1930, artifically-induced collapse has nearly doubled the collapse frequency in karst areas. In the state of Florida, insurance claims for damage from sinkhole collapse have increased from 35 in 1987 to 426 in 1991 (Smith, 1997). Federal Emergency Management Agency (FEMA), 1997 estimates cumulative damage in this state from sinkholes to reach $100 million.

Aside from damage due to surface collapse, sinkholes and related features cannot be considered negative aspects of karst terrain. Many sinkholes, sinkhole lakes and karst-related features in Florida are maintained as state parks for their aesthetic and recreational value (DevilÕs Millhopper, Blue Spring, Ichetuknee Springs, etc.). Florida Department of Environmental Protection, Recreation and Parks (FDEPRP) estimates that 14 million people visit Florida parks annually. This, along with privately maintained parks, provides millions of dollars in revenue for the state. But more importantly sinkholes and other karst features provide vital conduits for surface water recharge to the aquifer as breaches through the semi-confining layer. However, as breaches they also become sources of contaminants to the potable water supply. Consequently, sinkholes and sinkhole lakes need to be characterized by their hydraulic connection potential and subsequently maintained and protected if development of this terrain is to continue.