IMPROVED SINKHOLE MAPPING IN JEFFERSON COUNTY, INDIANA USING LIDAR TECHNOLOGY

Sinkholes are depressions in the ground surface generally associated with subaerially exposed carbonate rocks that undergo water dissolution over an extended period of time. This weathering process creates a surface depression or a void below ground, that either gradually enlarges as loose soil particles are drawn into the sink, or catastrophically collapses when the roof of the subterranean cavity is thinned and weakened. In areas like Jefferson County, Indiana, sinkholes are common, but are not studied or monitored regularly. The existing sinkhole map for Jefferson County is based on a survey of topographic maps provided by the Indiana Geological Society from more than fifty years ago. Remote-sensing data like LiDAR are extremely useful in recognizing and locating sinkholes for mapping, and in areas underlain by cavernous sinkholes, can lead to a decreased risk to property or injury from collapse if well monitored. Using LiDAR imaging, I aimed to improve the sinkhole mapping available in Jefferson County, Indiana. Using ArcGIS and LiDAR technology, I was able to identify 3,395 sinkholes in the study area, and the sinkholes I identified were compared to the state sinkhole map made in 2011 (using topographic mapping) with only 318 sinkholes. The differences between the number of LiDAR mapped and topographically mapped sinkholes are astonishing. In addition, I correlated the LiDAR sinkhole map that I developed to the geologic units and surface topography they are associated with to create a hazard map of the areas likely to form sinkholes in Jefferson County, Indiana. From this, I concluded that sinkhole formation dominates in Silurian and Ordivician sedimentary rocks in Jefferson County, especially near larger drainages. Sinkhole hazard mapping such as this could be applied to a wide swath of Indiana, Kentucky, and Ohio where carbonate rocks are exposed in the near surface if LiDAR data were more readily available.