ASSESSING SINKHOLE COMPLEXITY OVER TIME IN THE KARST TERRAIN OF DELAWARE, OHIO

The Ohio Department of Natural Resources, Division of Geological Survey has mapped karst in Ohio since 2009 using a statewide LiDAR-based digital elevation model that was created from data collected in 2006. After its original karst mapping in 2011, the Delaware region of central Ohio had additional higher-resolution LiDAR data generated in 2012. This additional data allowed for quantitative comparison of 2006 and 2012 sinkholes to assess growth, mitigation, and changes in complexity during that time. After refining the two LiDAR datasets into the polygons that represent the depressions, an established GIS model was used to create a complexity ranking, which is based on the shared spilling elevation of nested depressions. The rankings were compared, and preliminary results showed an approximated 10–20 percent increase in complexity for individual sinkholes, with some areas experiencing mitigation and/or new growth. This process also categorized sinkhole shapes to help geologists better understand morphology, which is tied to the relationship between formation mechanisms and development over time. Sinkholes in Ohio typically form slowly as previously existing fractures are opened by dissolution. Urban development in the Delaware region could exacerbate karst development, and the resolution increase between years may account for a small percentage of previously undiscovered sinkholes. As more LiDAR data is collected across Ohio, the database of ranked sinkholes can be used to identify and monitor areas of dynamic karst hazards for potential mitigation and further research.