Engineering landslide-proof highway construction in Karnataka’s ghat sections

In 2018, when Kodagu was devastated by one of the worst landslides in the history of this hilly district, the ghat sections of national highway (NH) 275 connecting Mangaluru and Bengaluru, via Mysuru, was left ravaged.

The number of landslips along highways has since steadily increased in the Western Ghat sections of Karnataka. This year, even coastal Karnataka was not spared. Landslips along NH-66, which connects Mangaluru with the northern parts of the country, claimed more than 10 lives in Ankola, in Uttara Kannada district.

Frequent landslides along the railway track in the Sakleshpur section of Western Ghats have disrupted the movement of goods and passenger trains for days on end.

Technical shortfall

BS Balakrishna, a former technocrat with experience in the highways sector, blames the unscientific slope cuttings and the gaps between the retaining walls and slopes for the recurrent landslides along highways.

Creation of stable slopes is a must while constructing roads in ghat sections, he says, adding that the flatter the slope, the more stable the roads will be.

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The pressure exerted on the retaining wall will be gradual if the wall abuts the slope that is being cut, he explains. If there is a gap, then the slightest movement of soil will shift the retaining wall, as happened in the ghat sections in recent times, he says.

He recommends creating longitudinal drains in the upper regions of the hill slope to ensure water does not percolate into the space between the retaining wall and the cut slope.

Incidentally, Karnataka Chief Minister Siddaramaiah, during his visit to the landslide-affected areas of NH-75 in the Shiradi ghat section, took officials to task for the steep vertical slope cutting along the highway.

Eco-sensitive plan

Niren Jain, an architect and environmentalist, calls for strategic regional planning to ensure minimal damage and durability when developing infrastructure such as roads, railway lines, pipelines, transmission lines, and canals in the Western Ghats. 

All future projects in the region should be developed along designated infrastructure corridors selected by experts on the basis of ecological, technical and economic feasibility, he suggests.

The experts should also determine the interval — say 100 km or 200 km — at which such infrastructure corridors should be established in the Western Ghats, leaving the rest of this sensitive ecozone untouched for conservation, he says.

Every year the government develops new infrastructure, or improves and/or expands existing infrastructure across the ghats, which leaves deep scars on the hillsides. There is no robust maintenance or management plan for this infrastructure either, he rues.

Ananthesh Prabhu, president of industry body Kanara Chamber of Commerce and Industry, points out that road and rail connectivity to New Mangalore Port’s hinterland passes through critical ghat sections. Loss of connectivity due to landslides has far-reaching economic consequences for the local populace and industries, he says.