Nepal Built a Highway Through the Himalayas — Then the River Took the Road Back

Nepal spent about two decades building the Sindhuli Road — also known as the BP Highway — through some of the country’s most difficult mountain terrain. Then, in September 2024, extreme rainfall transformed the Roshi River. But this was not simply a highway covered by floodwater. In some of the hardest-hit sections, the river eroded the bank and scoured away the ground supporting the road. Retaining structures lost support. Embankments collapsed. Entire sections of pavement disappeared into an enlarged river channel. The full BP Highway is roughly 160 kilometers long, and the entire road was not destroyed. More than 10 kilometers of roadway were reported washed away, while damage affected a much larger corridor. In this documentary, we explore how engineers originally built the Sindhuli Road, why the narrow Roshi Valley created such a difficult road–river engineering problem, what the 2002 flood had already revealed, how the September 2024 disaster attacked the highway from below, and how Nepal is now rebuilding the corridor. The story is not simply about a road destroyed by a flood. It is about a much harder engineering question: How do you build permanent infrastructure inside a river valley that is still physically changing? From mountain excavation and retaining walls to drainage, toe scour, riverbank erosion, temporary diversions and reconstruction, this is the full engineering story of Nepal’s BP Highway. Visual note: Some sequences in this documentary use engineering reconstruction and conceptual visualization to explain documented events and physical mechanisms. They should not be interpreted as original footage of every historical event shown. Subscribe for more documentaries about mega construction, impossible engineering, infrastructure failures, disaster engineering and the full process behind some of the world’s most challenging projects. #CivilEngineering #MegaConstruction #Nepal #HighwayEngineering #ImpossibleEngineering