LANDSLIDE HAZARD MAPPING IN NORTH CAROLINA - GEOLOGY IN THE INTEREST OF PUBLIC SAFETY AND INFORMED DECISION MAKING

The North Carolina General Assembly passed the Hurricane Recovery Act of 2005 in response to the deaths and damage caused by Hurricanes Frances and Ivan in western North Carolina in September 2004. This legislation appropriated funds for the North Carolina Geological Survey (NCGS) to begin county-scale landslide hazard mapping, ultimately to be completed for nineteen western N.C. counties. Prior to this appropriation, a grant through the North Carolina Division of Emergency Management (NCDEM) provided the NCGS start-up funding in 2003 to map geohazards. Slope movement hazard maps are complete for Macon County. An aggressive schedule calls for completing maps for Watauga and Buncombe Counties by July 2007.

The increased pace and magnitude of steep slope development are important public safety and political issues in western North Carolina. To help address these issues and guide informed decisions on development, the slope movement hazard maps are designed to provide technically and scientifically accurate, unbiased information. The maps show relative hazard rankings that are understandable to planners, policy makers and the general public. The maps also contain technical information on slope movement types and factor-of-safety-based stability index zonation that is useful to geologists and engineers involved in steep slope development. The Geographic Information System (GIS)-based maps consist of multiple layers and accompanying database information that show: 1) slope movements and slope movement deposits; 2) debris flow-slide initiation susceptibility; 3) downslope hazard zones; and, 4) geologic hazards. High-resolution LiDAR (light detection and ranging) digital elevation data and post-hurricane imagery, along with decades of previous soil and geologic mapping are critical data sets needed to make the maps.

Other ongoing hazard mitigation efforts include: public outreach presentations; issuing landslide hazard advisories in cooperation with the NCDEM, the National Weather Service and the U.S. Geological Survey; and, providing technical information to emergency management, local governments and the public. Information on landslide hazards, and slope movement-slope movement deposit data are available on the NCGS website (www.geology.enr.state.nc.us) and at www.nconemap.org.