PAMAP LIDAR: DISPLAYING DATA FOR LANDSLIDE AND KARST RECOGNITION IN PENNSYLVANIA

Comparison of images made using LiDAR-derived DEM data with historic landslide and sinkhole mapping and case studies provides a basis for developing techniques to expand to regional or state-wide hazard recognition in Pennsylvania. Different topographic settings and styles of landsliding require different processing for optimum recognition. Shallow debris avalanches on very steep slopes show best in hillshade images with false sun angle oblique to the slope aspect. Slumps in glacial lake clays are readily evident on slopeshade images, where steeper slopes are shown in darker shades. Sinkholes show clearly on slopeshade maps, while more subtle closed depressions in karst areas are more easily identified by the closed-depression contours.

Numerous landslide and karst features that were not identified on earlier maps can be found with LiDAR data, especially in heavily vegetated areas. Although some of these may have developed in intervening years, most are believed to have been missed in earlier mapping. Conversely, some previously mapped features are not evident on the LiDAR images, because of repair or “healing” of surface expression.

The PAMAP Program has been collecting and providing high resolution (1-foot) orthoimagery for Pennsylvania since 2003 and Lidar derived elevation data since 2005. LiDAR products are a 3.2-foot gridded DEM, 2-foot contours as a shapefile, breaklines and classified point clouds in LAS format. All data are in 10,000 foot-square tiles. All except the LAS files are provided free to the public via download from the Pennsylvania Spatial Data Access Clearinghouse (www.pasda.psu.edu). LAS files are available from the Pennsylvania State Data Center. LiDAR data for approximately 2/3 of Pennsylvania are on-line as of August 2009. Data for the remaining eastern third of the state were acquired in 2008 and are being processed and released as funds are available. Information on the program and data is at www.dcnr.state.pa.us/topogeo/pamap .