Soil Bioengineering Application and Practices in Nepal

Abstract

The small mountainous country Nepal is situated in the central part of the Himalayas. Its climate varies from tropical in the south to arctic in the north; and natural vegetation follows the pattern of climate and altitude. Water-induced disaster problems including soil erosion, debris flow, landslides and flooding are common due to the unstable landscape. Soil erosion is the most important driving force for the degradation of upland and mountain ecosystems. Soil bioengineering has been used in Nepal for nearly 30 years to deal with erosion problems on slopes, in high way construction and riverbank stabilization. The main soil bioengineering techniques used in Nepal are brush layering, palisades, live check dams, fascines and vegetative stone pitching. This study is based on the geology, climate and vegetation of Nepal and briefly summarizes the application of soil bioengineering on slopes and stream banks, with especial attention to the role of vegetation on slope and stream bank stabilization. Furthermore, this paper addresses the role of community participation and responsibility for successful application of vegetation-based techniques in management, maintenance and utility aspects for the future. In recent years, soil bioengineering techniques are extensively used due to their cost-effectiveness, using locally available materials and low-cost labour in comparison to more elaborate civil engineering works. However, scientific implementation and record-keeping and evaluation of the work are indeed essential.

Use of bioengineering techniques to prevent landslides in Nepal for hydropower development

“…The soil stability is driven by two major properties of plants. They are: (a) mechanical and (b) hydrological [7,11]. Increasing the shear strength of the soil is a function of plant roots, which is endorsed as a mechanical property [7].…”

“…They are: (a) mechanical and (b) hydrological [7,11]. Increasing the shear strength of the soil is a function of plant roots, which is endorsed as a mechanical property [7]. The roots form a network-like structure underneath the ground that binds and anchors the soil.…”

“…Slopes with a variation in altitude from 150 to 1500 m comprise immature sloping lands. They usually face the problems of deforestation and high amount of rainfall during the monsoon, which make them weak and prone to landslides [7]. Land topography also plays a significant role in deciding the appropriateness of any bioengineering technique.…”

“…Bioengineering techniques are applied vegetation-based techniques that use engineering practices integrated with ecological principles [3,6,7]. The fundamental principle of these techniques is that it takes the benefits of the biological and technical characteristics specific to natural vegetation, or in a combined form with living or non-living structures.…”

“…The common practices in Nepal against landslides include brush layering, palisades, vegetative stone pitching, live check dams, and fascines. Dhital [7] describes these methods in detail. Vegetation is used in soil bioengineering to reinforce and stabilize the slopes.…”