Roadside Landslide Prevention and Mitigation

Generally, the management of roadside landslide hazards takes place through reactive interventions (road clearance and repair) rather than proactive interventions (slope improvement and pre-emptive measures, such as retaining walls and bio-engineering applications).

Roadside landslide prevention and mitigation measures can be grouped into three: drainage measures, structural support measures, and soil bio-engineering measures.

Drainage Measures

Restoring natural drainage patterns is essential for the long-term effectiveness of landslide rehabilitation. Restoring drainage is recommended when landslides leave a steep headscarp at roads, cut across mid-slope roads, deposit debris onto a road, interrupt drainage patterns, or deposit debris in a gully or creek. Road drainage should be routed away from landslide tracks unless the landslide travels down a natural gully. Landslide debris should also be removed from road drainage structures. Lastly, too much water should not be diverted to a single culvert.

Structural Support Measures

Various types of walls such as gabion, stone masonry, composite masonry, etc. have been used to mitigate slope failures. Support structures such as rock bolts, earth anchors, anchored walls, etc. are also used. Usually, deep-seated landslides are treated with complex civil engineering structures, including large supporting walls, extensive drainage measures and technologies for anchoring unstable slopes to more solid ground.

Soil Bio-engineering Measures

Soil bio-engineering is the use of vegetation to reduce instability and erosion on slopes. It is relatively low-cost, uses local materials and skill, and provides livelihood benefits through economically useful products. The plants used can later become sources of firewood, grass, fodder, and maybe income.

Structural support measures can be applied in combination with drainage measures and soil bio-engineering measures. The improvements in the national highways of Nepal are a result of soil bio-engineering technology, which along with conventional civil engineering, has helped combat landslides. While standard civil engineering measures are usually required for the bigger failures, the more prevalent smaller problems can mostly be resolved using bio-engineering measures.

As human population grows and spreads, more road networks are produced. Consequently, the risk from roadside landslides increases. Roadside landslides are a threat to life and properties. However, numerous studies have shown that preventive and mitigation measures can be taken to minimize or eradicate the hazards and risks from roadside landslides.