The design and construction of the 240 km Koshi Highway in east Nepal between Dharan on the Terai Plain and Num in the Middle Himalaya commenced in the early 1970s and was completed in 2012 when the first vehicles were able to drive to Num. In a region where difficult terrain and geohazards pose severe challenges to highway engineering, geomorphological assessments have played an important and successful role in assisting route selection, detailed design of alignments, and the management of earthworks and drainage. These geomorphological assessments have also included the monitoring of slopes and watercourses to quantify geomorphological processes and assess the impact that road construction and operation have had on them. From an engineering geomorphological perspective, the Koshi Highway has proved a success and it demonstrates how careful design and control of construction operations can help limit physical impacts on the terrain, even in the most unstable parts of the landscape.

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