LIDAR, LANDSLIDES, AND THE (RAPID?) CONSUMPTION OF TRANSIENT TOPOGRAPHY IN THE BLUE RIDGE ESCARPMENT ZONE, SOUTHERN APPALACHIAN MOUNTAINS (Invited Presentation)

Landslides represent a threat to life, infrastructure, and property, and are also a key component of the hillslope-channel connection that delivers sediment to streams to drive topographic evolution. Landslide size, frequency and distribution may reflect a variety of forcings reaching beyond human impacts on the landscape or storm events. Remote sensing and field work are thus critical to determine landslide context and better inform hazard assessment. The rugged, transient topography of the southern Appalachian Blue Ridge Escarpment (“Escarpment”) provides a unique setting to explore the topographic context of landslide distribution with a 0.5-meter resolution lidar dataset. Lidar imagery reveals a dynamic landslide and debris flow history in this heavily studied landscape, with slope failures affecting colluvial accumulations, weathered rock masses, and minimally weathered cliff-type outcrops. In addition to historic slides affecting areas obviously altered by logging and road building, lidar reveals extensive older slide features and deposits of unknown age that represent natural events in the history of Escarpment hillslope evolution. Lidar suggests that landslide tendency is an intrinsic aspect of the Escarpment zone, with anecdotal evidence indicating slide density is higher at lower elevations along higher order streams. This pattern of slide distribution reflects both the transient nature of the regionally atypical Escarpment topography as well as the hillslope-channel connection in which landsliding plays a major role. Notably, “outlier” topography detached from the main Escarpment also hosts significant numbers of slides, indicating landsliding may remain an active and important component of topographic evolution of the small outliers as they progress towards closer resemblance to the surrounding Piedmont landscape. Lidar-derived imagery of the Escarpment zone emphasizes the importance of evaluating landslide processes within the context of the drainage network and overall topographic setting. Transient topography within an otherwise mature, slowly eroding orogen may still feature frequent landsliding as a component of locally accelerated topographic evolution in response to a dynamic stream network and progression towards equilibrium with long-term boundary conditions.