SLOPE STABILITY ALONG THE NORTH CAROLINA SECTION OF THE BLUE RIDGE PARKWAY

In 2000, the North Carolina Geological Survey (NCGS) began a project to produce geologic and geologic hazards inventories of the 250-mile long North Carolina portion of the Blue Ridge Parkway (BRP) and the Carl Sandburg Home National Historic Site (CSHNHS). Funded in part by the National Park Service (NPS), the project is scheduled for completion in September 2008.

The slope stability portion of the geologic hazards inventory includes developing a slope movement hazard map of the BRP corridor, a slope failure inventory, and a database with the following information: locations of slope failures and slope movement deposits (e.g. debris fans, block fields, etc.), failure dimensions, level and dates of slope failure activity, relevant rock structure information, field engineering and geologic rock and soil classifications, map units to demarcate relative potential for slope failures, and kinematic slope stability analyses. Mapping will be done at a 1:24,000- or 1:12,000-scale and will be provided to the NPS digitally in ArcGIS/ArcView^TM format.

Geologic hazards mapping to date consists of fieldwork in the central (the French Broad River near Asheville, NC to Blowing Rock, NC) and southern (the southern terminus near Cherokee, NC north to the French Broad River near Asheville, NC) segments of the BRP. Data is collected at locations with past, current, or potential slope movement activity. For rock slopes, RockPack^TM software is used to perform kinematic analyses and identify critical failure planes or intersections.

Types of slope failures along the BRP vary from debris flows to rock fall and rockslides. Remnants of Hurricane Frances in September 2004 triggered several embankment failures that mobilized into debris flows in the central segment. In December 2004 a past-active weathered rockslide at mile marker 401 reactivated due to freeze thaw and closed that section for over a week. In addition to concerns regarding public safety, slope failures have a negative affect on local economies that depend on tourism related to the BRP.

The first set of deliverables was provided to the NPS in June 2005. Work continues as access permits and is now focused on the southern segment. Slope stability studies along the BRP will be integrated into the NCGS landslide hazard-mapping program.