IDENTIFICATION OF TOPOGRAPHIC SETTINGS CONDUCIVE TO LANDSLIDING FROM DEM IN NELSON COUNTY, VIRGINIA, USA

The steep terrains in the Blue Ridge Mountains of Virginia are potentially vulnerable to landsliding. Hundreds of slope failures were initiated by a severe storm in 1969 in Nelson County, Virginia. The outlines of 87 landslide scars were delineated on aerial photographs within a 28.8 km(2) area. A digital elevation model (DEM) of the same area was constructed, from which three topographic variables (slope orientation, gradient and form) were derived. Overlay analyses of the landslide data and the topographic data, followed by chi-square tests, revealed that the topographic variables studied are statistically significant to the spatial distribution of the sites disturbed by landslide paths. While the landsliding potential is low at very low and high elevations, it is found to be high in the median range of elevation. West-, northwest-, north- and northeast-facing slopes are consistently more vulnerable to landsliding than their east-, southeast-, south- and southwest-facing counterparts. Terrains with a gentle gradient are stable, but the potential for landslides to develop increases greatly as the terrains become steeper. The slopes with a concave cross-section are more susceptible to landsliding than those having other shapes. Furthermore, the landsliding potential does not vary significantly with slope forms in the profile direction. It is concluded that the introduction of a DEM to this study has provided renewed insight into topographic settings conducive to landsliding which could not have been achieved otherwise.