In 1984, concern was expressed about the many shallow failures affecting slopes below and above some roads in Nepal. The Transport Research Laboratory (TRL) was commissioned to examine the possibilities for `low-cost' engineering measures for slope protection, which could be used in the Nepalese road maintenance routines, and examine the possible role of vegetation in slope protection. The approach was to observe regularly many sites, on which a wide range of techniques and vegetation types were used. Visits were made to Nepal from 1987 to 1992, during the late monsoon, when the sites were under most stress. The initial attempts at slope protection failed, because too little was known about the use of bio-engineering techniques to reduce shallow-located instability on steep slopes in the tropics. Many observation trials were conducted, with different treatments on each to discover the most successful techniques. Although the slopes were severely damaged in many of the experiments, lessons were learned from their failure. Eventually, combinations of vegetation systems and slope types emerged, which were resistant to slope instability. A methodology was developed for deriving a bio-engineering solution from a careful appraisal of slope conditions. A manual of bio-engineering for Nepal was published.
Abstract