Sinkhole distribution and characteristics in Pasco County, Florida

A statistical analysis of size, depth, date, frequency, and location was conducted of 168 reported new sinkholes in Pasco County. An average of twenty-four new sinkholes can be expected to form each year in Pasco County. The average sinkhole size is 10.23 feet in length, 9.15 feet in width, and 7.80 feet in depth. Seventy-five percent of these sinkholes will range from 0 to 10 feet in length providing a threshold target for foundation design engineers to limit sinkhole damage. Sediment cover thickness is the major factor controlling sinkhole development in Pasco County. Sinkholes are most common in the western half of Pasco County on the Gulf Coastal Plain where cover sediment thickness ranges from 0 to 100 feet. Most sinkhole occurrences in Pasco County form between March and May, the dry season, and, July and August, the rainy season. During the dry season the potentiometric surface level is lower, inducing increased flow of water from the surficial water table into the limestone of the Floridan Aquifer at depth. This increased flow of water washes sediment into cracks in the limestone forming cavities at the sediment/limestone interface. These cavities can potentially migrate to the surface causing sinkholes. During the rainy season, increased quantities of water deposited on the surface can induce greater flow of water into the limestone causing sinkholes in a similar manner.