Tunneling is a highly valuable underground construction technique utilized for transportation, communication, and utility services. In Nepal, with its challenging mountainous terrain, traditional methods of building highways and other transportation infrastructure pose a great difficulty. Natural hazards and disasters often lead to the failure of traditional highway construction methods like cutting slopes, retaining structures, and building bridges. As a result, tunneling has become a crucial method for building underground transportation passages in Nepal, despite the Himalayas being one of the most challenging regions for underground excavation. Despite difficult terrain, tunneling has been employed for centuries to construct underground structures and has become an indispensable aspect of modern infrastructure development. In Nepal, tunneling has long been recognized for its importance in the hydropower sector. Nevertheless, it is also equally vital in the highway sector as it offers a secure, efficient, and sustainable means of transportation. Tunnels provide a safe passage for vehicles, significantly reducing the risks resulting from falling rocks, landslides, and other natural hazards. Additionally, tunnels offer protection from extreme weather conditions, such as heavy rain, snow, wind, and unexpected flooding, making it safer for vehicles to travel.

Highway tunneling has a positive impact on the environment in Nepal. Tunnels minimize the need to construct roads through ecologically sensitive areas, reducing soil erosion and preserving natural habitats. They also help reduce air and noise pollution, improving air quality and reducing noise pollution in nearby communities. Moreover, tunneling helps to protect cultural and historical sites in Nepal as there is no need to construct highways that might damage or destroy such sites. Overall, tunneling provides a more sustainable solution for highway construction in Nepal, balancing the need for development with environmental protection.

Tunneling in the highway sector can provide an efficient means of transportation in Nepal due to its mountainous terrain. Tunnels offer a direct and safer route, reducing travel time and improving connectivity between regions, increasing safety, and facilitating a smooth movement of goods and services, which can boost trade and commerce and foster economic growth and development in the country. Nepal has made gradual progress in its infrastructure development by constructing several notable highway tunnels, including the Nagdhunga Tunnel, Siddhababa Tunnel, and three twin tunnels in the Kathmandu-Tarai/Madhes Fast Track (Expressway) Road Project. The Nagdhunga Tunnel connects the capital city, Kathmandu, with the southern part of the country, spanning a length of 2.68 km and featuring two lanes, making travel time more efficient for commuters. Although the project faced various challenges such as harsh weather conditions, waterlogging, and difficult terrain, it is on the verge of completion. The Siddhababa Tunnel, approximately 1.126 km long and situated on the Siddhartha Highway, aims to mitigate rockfall disasters along the Butwal-Palpa highway section, providing a safer and more reliable mode of transportation, especially during the rainy season when rock falls and landslides are frequent. The Kathmandu-Tarai/Madhes Fast Track (Expressway) Road Project is a strategic initiative aimed at connecting the capital city of Kathmandu with the southern Tarai region, which involves constructing three twin tunnels that span a combined length of 12.3 km. The project is currently under construction and is expected to become a significant catalyst for the region's development upon completion. However, Nepal’s expanding highway networks require substantial upgrades and new constructions to meet the country’s growing transportation needs. Introducing tunneling in highway upgrades and new construction, as has been done in the hydropower sector, would be a timely move for Nepal. However, it is important to note that tunneling is a complex and challenging process that demands specialized knowledge and expertise. Given the benefits of tunneling in highway construction in Nepal, as well as the institutional requirement to boost the country’s capacity for sustainable development of such mega-infrastructure, Nepal should focus on institutional development. This would involve developing a master plan for highway upgrades and new construction, conducting feasibility studies, and efficiently participating in construction, monitoring, and evaluations. Such an institution would require full-fledged capacity with appropriate technical, financial, and human capital strengths. Therefore, to ensure successful implementation of tunneling projects in the highway sector, the government of Nepal should invest in institutional capacity building. This would involve providing higher education and training to professionals working in this field, enhancing the financial, physical, and technical capabilities of institutions (construction companies), and developing local expertise while preparing the ‘highway upgrade and development’ master plan at the ministerial level. Such an investment would not only promote the use of tunneling but also create thousands of jobs for the local population. In conclusion, the construction of these tunnels in Nepal represents a significant milestone in the country’s infrastructure development. These tunnels provide safe and reliable transportation options while also contributing to economic growth and development. The successful completion of these infrastructure projects will help Nepal attract more investments and tourists, further boosting the country's economic growth and playing a vital role in employment creation at the local level. Overall, the progress made in infrastructure development in Nepal is a positive sign for the country’s future growth and development. As Nepal continues to invest in infrastructure development, it is likely that the country will continue to see positive economic growth via improved connectivity. The author is a disaster risk management expert/engineering geologist and is associated with Global Institute for Interdisciplinary Studies, Kathmandu, Nepal [email protected]