The Narayanghat-Mugling road in Nepal, a vital 33-kilometer section of the highway connecting Kathmandu with key trade points such as Birgunj and Bhairahawa, has undergone significant upgrades. This route is crucial for transporting around 90% of the country's trade volume to and from India and other nations. The highway, part of the Asian Highway Network, accommodates over 8,000 vehicles daily.
Previously narrow and susceptible to landslides due to its steep hills and proximity to the Trishuli River, this road posed safety risks and extended travel times. The World Bank supported its enhancement through the Nepal-India Regional Trade and Transport Project (NIRTTP), completed in 2021. The road was expanded from 5-5.5 meters to 9-11 meters, aligning with Asian Highway Network standards.
The project emphasized resilient construction by integrating slope protection measures using bioengineering techniques alongside traditional methods like drainage systems. This approach addressed challenges presented by difficult topography and climate-induced disasters exacerbated by the 2015 earthquake.
Nepal’s Department of Roads (DoR) managed the widening works. They excavated mountain slopes where necessary while constructing retaining structures on valley sides to minimize disturbance. Bioengineering solutions were implemented immediately after excavation with designs based on DoR's Reference Manual for roadside bio-engineering.
Engineer Shiva Khanal highlighted the importance of site-specific bio-engineering measures combined with effective water management: “It is critical to select bio-engineering measures suitable to the site-specific requirements with effective water management for preventing surface erosion.”
Advanced technology was introduced for complex slopes along the NM stretch that required detailed drone mapping and geotechnical assessments. Rohit Kumar Bisural, Project Manager at DOR, noted that these efforts reduced road closures during monsoons significantly: "The implementation and success of these treatment works prior to the monsoon period helped significantly reduce road closures during the monsoon."
Lessons learned from more than 100 slope stabilization projects have been documented in a supplementary guide published by DOR. Tuk Lal Adhikari, Expert Geotechnical Engineer leading investigations, stressed that proper investigation and design investments enhance resilience: “Investment in proper investigations, analysis, and designs for slope stabilization certainly pays back through increased resilience and sustainability.”
The upgrades have decreased travel time from two hours to just 50 minutes, improving trade efficiency. Gopi Parajuli, a truck driver familiar with this route, expressed relief: “Earlier, we were scared to drive on this road... Now, the road is much safer.”