Environmental correlations of landslide frequency along new highways in the Himalaya: Preliminary results

Variables which correlate with accelerated landslide activity are identifed in a study of two new hill roads at Almora and Nainital, U.P., India. Cumulatively, 32% of the roadcut is affected by rockfall and 27% by the slumping of rock and/or regolith. Correlation and discriminant analyses suggest that rockfalling may be predictable from measures of the frequency of enlarged joints in the roadcut supported by members of an inter-related complex of variables including slope angle, roadcut height, apparent dip, rock strength, and upslope vegetation cover. Direct measures of environmental instability, such as the undermining of the roadbed by erosion, were also shown to have value. However, the study found few useful environmental indicators of slumping. A positive relation between slumping and tree cover upslope may reflect the fact that forest survives as a relict landuse in locations which are undeveloped because of their instability.