A National Level Landslide Risk Index for Land Use Planning in Bhutan: Towards Assessing Landslide Hazard, Exposure, and Vulnerability Indexes

In Bhutan, landslides are a common natural hazard posing a greater impact on human settlements, infrastructure, and the environment. However, studies on the landslide risk to understand these impacts at a Gewog (smallest territorial units) level are limited. This study proposes an indicator-based approach to assessing the three risk dimensions; hazard, exposure, and physical vulnerability of buildings. The hazard component integrates a national landslide susceptibility index and an extreme precipitation susceptibility index. Exposure is assessed through population and building density, while vulnerability is determined by construction features such as construction technique and materials; number of rooms, and type of roofing, all weighted empirically. The final landslide risk index is derived by multiplying these risk dimensions. Cluster analysis further identifies key risk drivers across Gewogs. Results indicate that 47.5% of Gewogs (96) are at high to very high landslide risk, while only 19% (41) are at low to very low risk. High-risk areas are often rural Gewogs with dense populations and structurally vulnerable buildings. Additionally, 56% of houses nationwide fall into high or very high vulnerability categories. This integrative, localized risk assessment supports more targeted and context-sensitive landslide risk management strategies and offers a model adaptable to other regions for improved disaster risk reduction and land use planning.