RISK ESTIMATION OF HIGH PRIORITY UNSTABLE ROCK SLOPES IN GREAT SMOKY MOUNTAINS NATIONAL PARK, TENNESSEE AND NORTH CAROLINA

Great Smoky Mountains National Park along the Tennessee-North Carolina border is the most visited in the US. Unanticipated rockfalls occur within the park annually and often obstruct traffic flow and pose a significant risk to visitor safety. We developed a rockfall risk estimation model along the park’s primary roadways. Unstable slope data were collected using the Unstable Slope Management Program for Federal Land Management Agencies slope rating protocol. Out of 285 slopes, 280 were designated as localized rockfall, dominated by wedge and planar failure, and 130 slopes received a high unstable slope risk rating based on estimated rockfall hazard and human risk exposure factors. The rockfall locations, bedrock geology, distance to fault, elevation, mean temperature of coldest quarter, and annual precipitation data were used to prepare a rockfall susceptibility model using Maximum Entropy. The rockfall locations data were split into training (80%) and testing (20%), and the model yielded the area under curve values of 0.749 and 0.873, respectively. Mean temperature of the coldest quarter contributed most to rockfall potential, followed by slope steepness and then geology. A rockfall risk estimate model was prepared using Ordinary Kriging and Co-Kriging interpolation methods with the slope risk rating values and the susceptibility model as covariates. The Co-Kriging model produced a reasonable result with a standardized mean close to zero (0.003), small Root-Mean-Square (15.6), and Root-Mean-Square Standardized close to one (0.94). The rockfall risk estimate assists park officials in identifying high rockfall-prone areas and proactively maintaining the unstable slopes, ultimately improving visitor safety.