Potential Karst Features

This layer depicts potential Karst features in Tallahassee and Leon County, Florida. This layer is displayed with 45% transparency by default. This layer was developed using a 2012 LiDAR derived DEM. In 2012, the water table in Leon County was significantly lower that normal allowing for a better surface analysis of potential karst features. What is Karst and why is it important? Karst Waters Institute Karst is a special type of landscape that is formed by the dissolution of soluble rocks, including limestone and dolomite. Karst regions contain aquifers that are capable of providing large supplies of water. More than 25 percent of the world’s population either lives on or obtains its water from karst aquifers. In the United States, 20 percent of the land surface is karst and 40 percent of the groundwater used for drinking comes from karst aquifers. Karst features in Leon County are most fundamentally occur in depressions in the landscape. By delineating these depressions and analyzing their geomorphic characteristics, karst features can be mapped and classified according to their morphology. The process of identifying, delineating, and classifying karst features in Leon County is described below: Prepare Sink Depth Raster 1: Fill sinks in countywide 2012 DEM (This DEM was used because the water table was exceptionally low in 2012.) 2: Subtract original DEM from filled DEM to produce output raster of sinks with their depths Prepare Contour data set to be used for forming Sink Polygons 1: Create Z-negative 2-foot contours starting 1.5 feet blow the top of the sink. Smooth resulting contours 2: Convert closed contours to polygons 3: Merge polygons into multi-part features and explode into individual single-part polygons for each depression Prepare classified Potential Karst polygons 1: Eliminate polygons created from systematic noise in the Lidar-derived DEM 2: Review remaining polygons features and assign feature attributes based on geomorphic characteristics. The karst feature types were assigned based on the classification system published by the Florida Springs Nomenclature Committee Report: FGS Special Publication 52