Debris Slides in the Mt. Le Conte Area, Great Smoky Mountains National Park, U.S.A.

Bogucki, Donald

ABSTRACT: Rain gauge records show that on Sep- tember 1, 1951, more than 10 cm of rain fell in one hour over the Mt. Le Conte area, Great Smoky Mountains National Park. Numerous debris slides resulted from the cloudburst, and slide scars are still prominant features on the landscape. Three sections are identified within each slide track: the scar head, middle zone, and depositional zone. Slide dimensions vary considerably. Slide SB-10, largest in the Alum Cave Creek watershed, has a slope area of 10,500 sq m with an estimated regolith removal of 3,400 cu m. Slide ACC-3, smallest in the watershed, has a slope area of 154 sq m with regolith removal estimated at 62 cu m. Scar head slopes have a mean of 40 degrees, with a range of 35 degrees to 44 degrees. Intense rainfall, slope form, and compo- sitional layering of the Anakeesta Formation were significant factors for debris slide formation and location in the Mt. Le Conte area. Pedological, vegetational, and cultural factors may have also affected slide distribution, but after-the-fact analyses for these parameters make their exact function in slide activity unclear. The question of recurrence interval for slide producing storms essentially remains unanswered, although available data indicate that the return period may possibly be 100 years or longer. Introduction