COMMUNICATING ROCKFALL HAZARDS IN GREAT SMOKY MOUNTAINS NATIONAL PARK

Great Smoky Mountains National Park (GRSM) is the United States’ most visited National Park, receiving 11.4 million visitors annually. Each year, unanticipated road closures due to slope failure events occur within the park, requiring emergency expenditures and hampering park objectives. In this study, we utilized the Unstable Slope Management Program for Federal Land Management Agencies (USMP for FLMA) protocols to create an inventory of unstable slopes and evaluated their current hazard and risk conditions along the paved transportation corridors in GRSM. A total of 227 unstable slopes were studied along 186-mile-long roadway, of which 223 slopes were designated as localized rockfall, dominated by wedge and planar failure mechanism. 100 sites received ‘poor’ unstable slope rating based on human risk factors and estimated rockfall event properties. Aerial imagery from 2008 and 2012 were used to create Normalized Difference Vegetation Index (NDVI) and false color imagery; while no change was detected, several user-rated unstable slopes were validated. An optimized hotspot analysis was conducted; the study identified five clusters concentrated along primary roads. Overlay Analysis was used to compare relationships between clusters of unstable slopes and the region’s geology. Unstable slope clusters are primarily in the Great Smoky Mountain Group specifically, within the Anakeesta Formation, Thunderhead Sandstone, and Metcalf Phyllite. The inventory database of unstable slopes with individual risk rating, pattern of change in the slope condition over time, and knowledge of the hotspots will allow researchers to more effectively communicate the present conditions with park officials. The study will also help prioritize areas for further investigations with the ultimate aim to improve safety for park visitors.