Assessment of slope-cut landslides along Pokhara-Baglung Highway, Nepal

Abstract

The study addresses the ramifications of development initiatives in delicate mountainous terrains, unveiling significant economic constraints and multifaceted environmental challenges. It focuses on investigating substantial landslides triggered by excavations along a specified stretch of Nepal's Pokhara-Baglung Highway. This research holds significance for policymakers engaged in devising highway development strategies that mitigate future landslides, minimizing both costs and the toll on life and assets. The investigation encompassed on-site cataloging of landslides, lab test of sampled soils and a structured questionnaire distributed among local residents. This comprehensive approach facilitated a thorough assessment of landslide occurrences and their consequential effects. The identified landslides exhibited a consistent rotational pattern, characterized by abundant quartzite and phyllite rock formations. The predominant soil composition consisted of fine-to-medium sands, exhibiting a Plasticity Index (PI) range of 0.5 to 3, indicating marginal plasticity. Significantly, a substantial portion (70%) of the populace reported tangible impacts from landslides, with about 32% of affected individuals confirming an average agricultural productivity loss of 4330 kg/km2. Statistical analysis using the Chi-square test indicated a uniform impact across various demographic categories, including gender, education, proximity to the affected site, and social caste. Although fluctuations in the region, the observed temporal precipitation consistency over decades suggests as an accelerating rather than primary causative factor for landslides. Thus, principal causes of slope failures predominantly link to inadequately managed bedrock excavations and suboptimal road drainage systems underscoring the necessity for systematic inquiries into soil stability post-slope incisions. These measures are pivotal in guiding the construction and expansion of road networks within Nepal's Himalayan region.