USING LIDAR AND HIGH-RESOLUTION AERIAL PHOTOGRAPHY TO MAP KARST IN DELAWARE COUNTY, OHIO

The Ohio Department of Natural Resources Division of Geological Survey (OGS) in collaboration with the Delaware County Soil and Water Conservation District (DCSWCD) are analyzing the six 7.5-minute quadrangles covering western Delaware County (OH) to document and geo-reference known and newly identified karst features within the map area. DCSWCD’s desire for this information is two fold: 1) identification of potential groundwater pollution pathways and engineering concerns and 2) preventative development planning for the fastest growing (residential) county in Ohio. The OGS’s interest is related to its mission to document potential geohazards in Ohio. Having good geologic data will help the DCSWCD and Delaware County Planners minimize the potential environmental impact of infrastructure installations and improvements and residential and commercial development. This type of mapping project is field intensive. To make OGS’s field time more productive an innovative computer processing technique was developed which involved the processing of LiDAR data to identify closed pits on the LiDAR generated Digital Elevation Model (DEM) surface. The resulting closed pit features were combined with high-resolution (6-inch per pixel) aerial photography and compiled into a GIS project. The GIS project permitted geologists to mark the indicated feature for field verification or to remove it based on observable information (i.e. obvious road culvert or sewer) on the high-resolution aerial photography. During the GIS analysis geologists also marked probable, photo indicated karst features for field verification. The field verification phase of the project began in late November and is projected to be completed by mid to late-April 2010. Initial field verification is confirming the utility of using LiDAR to indicate probable karst features but also the need for field verification. The resulting GIS layer will serve as a starting point to begin analyzing the impact of karst on the hydrogeologic environment of the Scioto and Olentangy River corridors in central Ohio, provide information on potential engineering impacts, and for establishing better groundwater protection guidelines.