MORPHOMETRIC AND SPATIAL DISTRIBUTION PARAMETERS OF KARSTIC DEPRESSIONS, LOWER SUWANNEE RIVER BASIN, FLORIDA

Abstract

Surrounded by submarine escarpments from both east and west, the Florida Platform consists of a thick sequence of lime- stone and dolomite deposited during the Tertiary Period. The generally unconfined or semiconfined hydrogeologic condi- tions of the Floridan aquifer system in the lower Suwannee River Basin have produced a fascinating collection of karst depressions illustrating a complex evolutionary history con- trolled by the lower sea-level stands of the Pleistocene and the formation of the Suwannee River (Denizman & Randazzo 2000). Morphometry can be defined as the measurement and mathematical analysis of the configuration of the Earth's sur- face and of the shape and dimensions of its landforms (Bates This study describes an application of Geographic Information Systems (GIS) to examine the morpho- metric and spatial distribution of karstic depressions in the lower Suwannee River basin. Morphometris analysis of some 25,000 karstic depressions in an area covered by twenty-four 1:24,000 scale standard USGS topographic quadrangles were made possible by the analytical capabilities of the GIS. The para- meters calculated for the study area include length, width, orientation, area, depth, circularity index, depression density, pitting index, and nearest neighbor index. Analysis of ~25,000 depressions in the lower Suwannee River basin reveals that the Florida karst is represented by broad, shallow depressions with an average density of 6.07 depressions/km² and an average pitting index of 14.5. Morphometric and spatial distribution parameters of karstic depressions within the lower Suwannee River basin show sig- nificant variations. The robust GIS methodology used in this study provides not only a rapid analysis of spatial data on a large population of karstic depressions, but also an objective approach with consistent measurement and calculation processes in which human errors and bias were eliminated. In accordance with the increas- ing use of GIS in analyzing spatial data on diverse applications, this study shows that the GIS environ- ment can also be efficiently used for karst landform studies.