Treading a rocky path

DURING the ongoing monsoon, there has been a series of devastating landslides in Himachal Pradesh. About 700 roads, including four national highways, have been damaged. The loss is estimated to be over Rs 10,000 crore. The Kalka-Shimla highway has been badly affected; at least six landslides have been reported on the 50-metre stretch between Chakki Mod and Sanwara. The Parwanoo-Dharampur section remains affected, too, as a 250-metre portion of the road is sinking. The Kullu-Manali section has been washed away at many places; several buildings have collapsed like a house of cards.

The Tribune Debate: Flood fury in HP has underlined the fragility of the Himalayan region. Preventive steps are a must to arrest the slide

Monsoon-related disasters such as landslides, cloudbursts, floods and flashfloods are not new to the hills. In order to understand the causes of landslides and immense destruction in Himachal Pradesh, one must examine the geological framework of the Himalayan mountain system. Formed due to the collision between the Indian and Eurasian tectonic plates some 60 million years ago, it is still tectonically active. The collision made it unstable due to the processes of folding, faulting and thrusting. In geological terminology, a thrust fault is a tectonic lineament along which older rocks are juxtaposed on to the younger ones, thus reversing the sequence. This phenomenon makes the mountain system prone to landslides. Himalayan zones include the Outer Himalayas, whose Shivalik range is ‘overthrusted’ by the Sub-Himalayas. The Higher Himalayas are separated from the Lesser Himalayas by the main central thrust — which is defined as a major geological fault where the Indian Plate has pushed under the Eurasian Plate along the Himalayas — and the whole sequence is cut transversely by faults.

A landslide is defined as the movement of a mass of material down a slope. It includes displacement by falling, toppling, sliding and flowing due to gravity. Landslides are triggered by heavy monsoon rainfall, seismicity and anthropogenic activity. Various cases of mass movement are due to endogenic processes, thrusts, faults, slope characteristics, topographical relief, drainage and land use.

As early as 2010, The Tribune had carried a report on the cutting of slopes for four-laning the Shimla-Parwanoo section. The road was upgraded to a national highway in the 1970s. Cutting hills to broaden the road destabilised a large stretch; its blockage by landslides became a common feature.

It took almost three decades to stabilise the hills by erecting retaining walls and planting trees. The Himalaya Niti Abhiyan, an NGO, had urged the government to explore alternatives to four-laning. At some places, vertical cutting (90°) has taken place, whereas the slope angle should have been less than 60°.

The faults and other lineaments should have been avoided. Natural water channels have been blocked, thereby allowing water to percolate down the hills, causing erosion of soil and building foundations and making them vulnerable to landslides. The area falls under seismic zones IV and V.

I wonder if the expert opinion of the Geological Survey of India or the state Geology and Mining Department was obtained, not only for constructing highways but also for raising buildings in the hill terrain. A geological investigation, soil survey, good engineering practices and efficient enforcement of land and management regulations can reduce the landslide risk.

Blasting of rocks by dynamite for widening of roads or tunnelling impacts the stability of the slopes. Rain/snow makes it worse, thereby causing sliding and slumping.

The Kalka-Shimla geological section, which was studied by British geologists and is part of textbooks, has been completely lost due to cutting, leaving no trace of outcrops along the highway.

There has been incessant plunder and overloading of the hills. Multi-storeyed buildings have eaten into the tree cover, blocked surface runoff channels and destabilised slopes. Rivers in spate are spreading beyond their floodplain limits. Man-made follies are wreaking havoc on humans and nature.

The belief that concrete structures of reinforced cement can offer resilience and strength is proving to be a fallacy. The Shiv temple at Summer Hill in Shimla was buried under rubble and Krishna Nagar was hit by landslides. It has been reported that excavations were going on at the rear of the temple. Kullu has witnessed heavy landslides.

It’s time to use ISRO satellites with SAR (Synthetic Aperture Radar) data. Lives can be saved by prior assessment through SAR. Geological movements can be discerned by remote sensing.

Rapid infrastructure development and unplanned urban growth have taken place without taking into consideration the strength of the bedrock, seismic building codes and other geological parameters. It must be remembered that no pillars are stronger than the rocks they stand on.

Disaster management does not involve huge expenditure. It entails an ecosystem analysis before planning every big project and demonstrating zero tolerance to illegal constructions.

Himalayan states need land use maps based on geoscientific and structural engineering designs to ensure the safety of people. Designs of old houses can be integrated with those of modern ones. The devastation in Himachal Pradesh has brought the focus back on traditional architecture.

All said and done, it is not nature but our disrespect for it that kills people. Ecology and geology are natural sciences and we should obey their laws. Development should not harm the fragile Himalayan ecosystem. We should respect the imposing Himalayas so that they remain benevolent to us.