THE PRACTICAL APPLICATION OF LIDAR TO EVALUATE POTENTIAL RELATIONSHIPS BETWEEN LINEAMENTS, GEOLOGY, STRUCTURE, AND LANDSLIDE OCCURRENCE IN THE BLUE RIDGE OF NORTH CAROLINA

The North Carolina Geological Survey's (NCGS) landslide hazard mapping in western North Carolina is founded on a GIS platform whose raster base maps are derived from 6-m LiDAR (Light Detection and Ranging) recently made available by the North Carolina Floodplain Mapping Program. These digital products have opened new doors for evaluating potential relationships between geology, structure, and landslide occurrence in the Blue Ridge, particularly when conducting analysis of linear geologic features. Historically, lineament analysis was performed using aerial photography (landscape often obscured by vegetation), low-resolution topographic contour maps, or 10-30 meter USGS digital elevation models (DEM). High resolution, 6-m LiDAR has resulted in maps of the landscape that are “bare earth” (i.e., vegetative growth removed). A derived DEM and several “hill shade” maps, depicted at differing sun angles and azimuths, allow manual interpretation and digital tracing of geological lineaments into GIS (automatic lineament detection techniques using GIS are still being tested). The resulting digital lineament traces of varying length and orientation can be separated into populations and statistically evaluated. Linear trends reflecting topographic ridges and troughs can be further interpreted as brittle/ductile structural features (fractures, faults, etc.), and in some cases, geologic contacts. Several examples of these applied techniques will be presented from the NCGS's landslide hazard mapping of Macon and Watauga counties. The use of LiDAR provides the resolution to view features at varying scales to speed geologic mapping by focusing field investigations and enhancing the ability to test already established ideas.