Characterization of cover-collapse sinkhole morphology on a groundwater basin-wide scale using lidar elevation data: A new conceptual model for sinkhole evolution

In karst regions of the world, identifying areas that are inherently unsafe for certain types of land use is crucial. High-resolution lidar elevation data for the Illinois sinkhole plain have exposed previously unnoticed geomorphologic details. Analysis of these data has revealed a pattern of long-term evolution of cover-collapse sinkholes within the groundwater basins. The leading edge of a groundwater basin is known to be the site of progressively enlarging bedrock crevices and conduits that encroach into groundwater divides. In karst areas of the U.S. Midwest, runoff creates surface streams at groundwater divides that flow into groundwater basins and form disappearing streams. Using this pattern as a starting point, we developed a new conceptual model of cover-collapse sinkhole development and evolution within groundwater basins. As the boundaries of a groundwater basin migrate outward for tens of thousands of years, stream-valley-shaped sinkholes at the leading edge seemingly migrate deeper into the basin. The stream-valley sinkholes then form numerous drains, join other sinkholes through erosion and collapse along sinkhole boundaries, and eventually become areally extensive and irregularly shaped compound sinkholes. Continued erosion of fine-grained sediment overlying bedrock near the distal end of the groundwater basin reduces the elevation of land surface until nested sinkholes within the compound sinkholes become simple sinkholes with a single drain point. Near the discharge points of the groundwater basin, the individual drains associated with the simple sinkholes partition the remaining upland surface, forming a pattern of Thiessen or Voronoi polygons resulting from surface runoff among adjacent sinkholes.