LIDAR: A POTENTIAL TOOL FOR MAPPING OF SINKHOLES AND KARST IN DRIFT-MANTLED AREAS

Karst occurs in Illinois where bedrock outcrops and subcrops consist of carbonate strata (approximately 25% of the state by area). The state, however, is largely covered by Quaternary glacial deposits and even the non-glaciated areas are blanketed by thick to thin loess deposits. Delineation of Karst regions (about 10% of the state) has been accomplished by the mapping of caves, sinkholes, and springs using a combination of topographic maps and aerial photography, and study of geologic maps and previous reports. In karst terrain, sinkholes are probably the most obvious karst feature, but not all sinkholes are readily detected on topographic maps because the contour interval is too large for many sinkholes, or on aerial photography because of thick vegetative cover, especially wooded areas. LIDAR, with its capability of generating “bare earth” Digital Elevation Models (DEMs), has a strong potential for the precise mapping of sinkholes. This potential is illustrated by study of DEMs derived from LIDAR data of an area covering the northern edge of Pulaski County and the southwestern corner of Johnson County in southernmost Illinois. A small portion of this area is underlain by shallow carbonate bedrock. The LIDAR-derived DEMs of several sites indicate the occurrence of both individual sinkholes and clusters of sinkholes that are not identifiable on either topographic maps or aerial photography. The availability of LIDAR throughout the state or the nation would be a valuable tool which would increase the precision of sinkhole mapping and result in a more accurate delineation of Karst regions.