Landslide Mapping and Inventory Status in Pennsylvania

The Pennsylvania Geological Survey and the U. S. Geological Survey have mapped and collected information on landslides in Pennsylvania intermittently since at least the 1960s. Nearly 50% of the state has some landslide mapping available. In response to renewed interest in possible land development regulation in geologic hazard areas, the Pennsylvania Geological Survey has posted scanned copies of 295 7.5-minute quadrangle Landslide and Related Features maps (USGS open-file from 1978-1981) to the bureau web site at www.dcnr.state.pa.us/topogeo/. We have added links to other online publications (mostly from the USGS) and information about print publications.

The PAMAP program will begin release of statewide Lidar elevation data in summer of 2008, with 3.2-foot gridded DEM and 2-foot contours. These new datasets offer an unprecedented opportunity to update and improve landslide inventory mapping, and for GIS analysis of topographic and geologic occurrence patterns of landslides.

Increasing use of GIS in our mapping has included development of a landslide geodatabase and initial digitizing of the landslide data from the Williamsport 1 x 2 degree quadrangle and six 7.5-minute quadrangles in the Pittsburgh area. These would serve as prototypes for a statewide inventory of landslide features.

Existing map inventory is supplemented by case files of individual slides known to survey staff through reports or direct investigations. Although far from complete, these files add information on time and type of occurrence, and in some cases cost and damage data.

A legislative task force, responding to a major slide event in Pittsburgh in 2006, has prepared draft legislation, which if passed, may direct DCNR, through the Topographic and Geologic Survey, to prepare new statewide geologic hazard maps. Information from the shared wisdom gained from the USGS and State Survey Landslide Inventory Steering Committee will provide an important foundation for future landslide mapping and inventory work in Pennsylvania.