Optimal Preliminary Highway Alignment, with Slope Disaster Risk Management, in Himalayan Regions

Abstract

This paper proposes a preliminary highway alignment optimization model incorporating slope disaster risk management. Previous research in highway alignment optimization has not considered detailed slope instability conditions. Various types of natural disaster–-including landslides, slope failure, floods, and earthquakes–-are common in the Himalayan regions because of rugged topography and fragile geology. Construction of highways in the area disturbs naturally formed slopes, resulting in instability on the slope. An inclusive slope failure susceptibility map was prepared by considering various types of landslide-controlling factors including lithology, slope, aspect, land use, drainage density, stream drop, distance to stream, and distance to lineament. In addition to slope failure susceptibility layer, land acquisition cost, slope, land use, and unit cost of earthwork excavation are considered when optimizing highway alignment. The process was done in a geographic information system environment in a case study investigating the influence of the slope failure susceptibility condition in alignment optimization. Preliminary alignments were searched in a cost-weighted distance raster created with and without considering slope failure susceptibility condition, whose influence is noticed distinctly with respect to location and length of alignment. Alignments obtained from preliminary optimization were compared with previously proposed alignments, and newly optimized alignments verify the previous studies. The main limitation of this study–-that it could not consider all cost functions–-will be considered in future work.