Disaster Mitigation of Debris Flows, Slope Failures and Landslides 503 Roadside Slope Failures in Nepal during Torrential Rainfall and their Mitigation

Nepal is a mountainous country situated in the heart of the Himalaya. The Himalaya is also famous worldwide for its very active tectonics. In Nepal, over 80 % of the rainfall occurs within a short three months during the monsoon period and extreme rainfall events are very common such as over 400 mm of rainfall can occur within 24 hours. Thus, these geological and climatic factors make the mountain slopes of Nepal most susceptible for rainfall triggered landslides. In Nepal, to provide transportation facilities to all people, in last ten years, road construction projects are considered as a major part of infrastructure development and the growth of the roads shows exponential increase from 376 km in 1950 to 15,308 km by 2000 within a period of 50 years. In which nearly half of total road length is earthen roads. These road construction and maintenance programs are widely affected by both shallow and deep seated landslides triggered by monsoon rainfall. This paper comprehensively deals with roadside slope failures during torrential rainfall events in major road of Nepal such as Tribhuvan Highway, Siddhartha Highway, Prithivi Highway, Arniko Highway, Dhulikhel-Sindhuli Road