Subbottom Profiling Investigation of Sinkhole Lake Structure in Bay and Washington Counties, Florida

Abstract

It has long been common knowledge that the lakes have sinkhole origins (Grubbs, et al., 1995; Pratt, et al., 1996), but after viewing shorelines during periods of drought when lake levels drop, it was suspected that the mode of creation and growth was complex as demonstrated by the “string of pearls” appearance of new, smaller depressions forming around the perimeter of the lakes (Figure 2). In addition, there were questions regarding the interaction and connection between the lakes, the underlying surficial (unconfined) aquifer, and the deep, semi-confined Florida aquifer system (FAS). As a means of developing an understanding of lake structure and growth mechanisms as well as an understanding of the interconnection between the lakes and the FAS, a program of marine (lake) geophysical imaging was conducted in five sandhill lakes in the region. The method applied is high resolution seismic reflection profiling or sub-bottom profiling. Abstract The sandhill lakes of Bay and Washington Counties, Florida, are deep, pristine environments which owe their existence to sinkhole activity as observed in limited bathymetric maps and in the appearance of small circular depressions around their perimeters (“string of pearls”) observed on aerial photography especially during low water level periods. However, little investigative information exists that shows the internal, deep structure of these lakes and how that structure might affect interaction with groundwater flow and lake levels.