USING AN INVENTORY OF UNSTABLE SLOPES TO PRIORITIZE PROBABILISTIC ROCKFALL MODELING AND ACID BASE ACCOUNTING IN GREAT SMOKY MOUNTAINS NATIONAL PARK

An inventory of unstable slopes along transportation corridors and performance modeling are important components of geotechnical asset management in Great Smoky Mountains National Park. Rockfalls frequently occur in the park, often initiated in highly weathered, fractured metasedimentary rocks. In this study, an inventory was created using the Unstable Slope Management Program for Federal Land Management Agencies protocols. Rockfall hazards and risks were evaluated for 280 unstable rock slopes along 151 miles of roadway. Kernel Density Estimation was used to identify four clusters and establish study areas for site-specific analysis. Site selection was based on six criteria: risk and hazard density surfaces, slope, proximity to map-scale faulting, proximity to roadway, and the predicted acid-producing potential of geologic units. A weighted-overlay multi-criteria model was created, and fourteen sites were selected for two-dimensional probabilistic rockfall simulations to predict rockfall pathways. Additionally, Acid Base Accounting tests were performed at each location to evaluate the acid-producing potential of the exposed rocks. Simulations indicate that rock material would likely enter the roadway at all fourteen sites and suggest that runout distance is inversely related to the width of the ditch. Acid Base Accounting test results indicate that influence of significant acid-producing potential is generally confined to slaty rocks of the Anakeesta Formation and graphitic schist of the Wehutty Formation. The research illustrates a repeatable approach for prioritizing areas for more time intensive and costly site-specific investigations towards the goal of improving safety in the most visited national park. The results can help park officials develop strategies for rockfall related risk mitigation and acid rock management.