Landslides outcome of damaging environment

Rakesh Lohumi

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The spate of destructive landslides in Himachal during the current monsoon has brought to the fore the perils of unregulated and excessive anthropogenic activities in the geologically unstable and environmentally fragile Himalayan mountain ranges. 

A few hours of heavy rain early this week triggered off thousands of landslips across the state. Life was thrown out of gear as landslides and flowing construction debris blocked 923 roads, ranging from rural link roads to national highways. A number of lives were lost, as houses and vehicles were either buried under debris or suffered extensive damage. 

The high seismicity and precipitous terrain make the entire mountain ranges highly prone to landslides. According to the geological survey of India, 97.42 per cent of the state’s total geographical area is susceptible to landslide hazard and not surprisingly landslide is the most common occurrence. However, the most problematic are the areas falling in very high-risk zone (14.27 per cent), followed by high-risk zone (70.07 per cent) where major landslides occur. The intensive human activities, particularly in the steep mid- and high-altitude areas, are making the mountains more and more vulnerable to landslides. Kullu district has the maximum 33.70 per cent area in the severe landslide hazard risk category, followed by Chamba (33.28 per cent), Solan (29.11per cent), Mandi (25.01 per cent), Bilaspur (18.91 per cent), Shimla (17.79 per cent) and Kinnaur (13.73 per cent). 

The scale and frequency of such disasters has been increasing alarmingly due to man-made factors like large-scale deforestation, unscientific construction of roads, haphazard urbanisation, illegal mining, setting up of hydropower plants and other development activities. Only last year, 46 people perished in a massive landslide at Paddar in Mandi district, as an entire hill turned into a huge mudslide and the swirling debris overran about a dozen vehicles and a number of shops and houses lining the Mandi–Pathankot national highway around midnight. There have been several fatal incidents of landslips and falling rocks, swallowing moving vehicles on various roads, including the Kullu–Manali, Shimla-Parwanoo highways. 

The large number of ongoing road projects has been to a large extent responsible for the destabilisation of hills. The deployment of heavy earth-moving machinery by big companies, implementing express highway projects in the BOT (Build Operate and Transfer) mode has made things worse. The ongoing Parwanoo-Solan four-laning project provides a glaring example of improper designing and poor execution.  Trees have been axed in thousands and large stretches of precipitous hills have been cut almost vertically without bothering about the geological implications to widen the road, instead of laying bridges and boring tunnels. Laid bare and shaken by reckless mechanical excavations, the loose hill strata could hardly withstand rain, which set off numerous mudslides to block the highway at many places. The slopes destabilised by unscientific excavation will take decades to settle down. 

“Slope cutting has to be carried out scientifically, keeping in view the nature of strata to ensure stability. Instead of large-scale vertical cutting of the fissured and fragmented rock strata, bridges should have been constructed,” says Satish Sagar, national quality monitoring consultant for the Pradhan Mantri Gramin Sadak Yojna.  

He said widening of highways also provided an opportunity to improve the road geometry, but in case of the Parwanoo-Solan highway, no effort had been made to smoothen the sharp curves and this could make it prone to accidents. A smooth riding surface of the four-lane will encourage motorists to drive at a high speed, but they would be at considerable risk while negotiating the sharp curves, he explained.

The National Green Tribunal (NGT) took serious notice of the reckless manner in which these projects were being executed and issued directions in a number of cases but there has been little improvement. 

According to Naresh Sharma, a former Engineer-in-Chief of PWD, the only way out was to ensure that detailed project reports for road projects were made after extensive field surveys, so that there were no geological surprises and the final alignment, extent of hill cutting and specification of retaining structures are clearly specified. Earlier, during manual excavations cutting the hillside was not the preferred option and very little debris was generated and disposal was not a problem. Proper retaining structures were provided to stabilise the slopes. 

Failure to provide proper drainage, particularly cross drainage, also aggravates the problem of landslides, as storm water floods the road and then flows in a torrent downhill, creating new gullies by eroding the slopes. The dumping of debris on slopes adds to the problem, as it is washed down into ‘khads’ and streams, which often change course due to the burden and cause massive damage in the areas downstream. With the availability of heavy earthmoving machinery, roads are being constructed on private and village common land by builders without bothering about drainage or disposal of debris. Some of the stretches along main highways have become permanent landslide points. The maximum number of active landslides was in tribal Kinnaur district at Jhakri, Pangi, Powari, Urni, Sholdan, Nichar, Khadra Dhank, Thangi, Barua, which repeatedly block the Hindustan-Tibet Road. Shimla-Parwanoo, Mandi- Jogindernagar, Chamba-Dalhousie, Shimla-Rampur, Shimla-Bilaspur and almost all roads in Lahaul and Sipti fell in the extremely vulnerable zone. 

The Union Minister for Road Transport and Highways, Nitin Gadkari, has announced upgrade of as many as 61 state roads to national highways. The manner in which projects are being implemented in utter disregard of environmental norms, the situation will become worse if all planned projects are executed.

There are thousands of sites where the land mass is constantly sliding and the situation worsens during the rainy season. Unscientific land use coupled with haphazard and excessive urbanisation have overburdened the fragile slopes. Trees have been axed with impunity and multi-storied structures have been raised by cutting the hills vertically. Some of the buildings hang precariously on the edge of precipitous hills and give a scare to the onlookers. The situation has worsened, as successive governments, instead of strictly enforcing building laws, rewarded the offenders by bringing repeated retention policies between 1999 and 2014. It made a mockery of the Town and Country Planning Act by enacting legislation last year to regularise all illegal and unauthorised structures across the state on “as is where basis is”.  The High Court quashed the amendment in December last year, but the verdict has not been implemented and unauthorised construction is continuing unabated.

The landslides in urban areas are mainly on account of excavations carried out for the construction of multistoried buildings on steep hills in violation of slope density norms which prohibit construction on slopes with a gradient of 35 degrees or more. While only single-storied structures with attic are permitted on slopes of 25 to 35 degree, subject to the condition that 90 per cent of the site will be kept in its natural state, three-storied structures could be raised on slopes of 15 to 25 degree. In Shimla and Solan districts, six to eight-storied structures have been erected on 70-degree slopes.

The debris generated during excavation is mostly dumped on slopes and this is the main cause of increasing landslides in urban areas even as precipitation is declining. Rainfall data gathered by Bhakra Beas Management Board also shows a steady decline in precipitation during the monsoon in the catchment area of the Sutlej and Beas rivers. The total rain in the catchment area from June to September has come down from 1,092 mm in 2008-09 to 621 mm in 2018-17, an alarming decline of 44 per cent in less than 10 years. The main reason is that the surface runoff has increased due to excessive construction on hills. Vast stretches of lush green have been transformed into concrete hills with buildings coming up on slopes virtually one over the other. Even a moderate spell of rain causes ‘khads’ and drains to overflow.

Unauthorised constructions apart, huge hotels, commercial buildings and apple orchards have come up on forest land illegally. Besides, 13,027 hectare of forest land has been diverted for hydropower projects and transmission lines (7,458 hectare), roads (3,128 hectare), mining (918 hectare) and other non-forestry use up to March 31, 2018. The state needed to conserve, extend and improve the quality of its forests all the more, as it lags far behind other Himalayan states, except Jammu and Kashmir. It has just 15,100 sq km (27.12 per cent) of the total geographical area under the green cover, as per the latest State of Forests Report (SFR)-2017. Even the more populous state of Uttarakhand, which has a slightly less area of 53,483 sq km, has a much larger area of 24,295 sq km (45.43 per cent) under forests. 

More importantly, the quality and expanse of forests in the high-altitude areas have been declining progressively. The areas under very high-density forests (with tree canopy density above 70 per cent) has come down from 3,224 sq km in 2009 to 3,110 sq km in 2017, while the area under degraded  open forests (with tree canopy density between 10 to 40 per cent) has increased by 224 sq km. The forest cover in most fragile high-attitude zone beyond 3,000 m, where regeneration is a Herculean task, dipped alarmingly from 2,489 sq km to 1,880 sq km over the period. The increase of 895 sq km has been in the lower-hill ranges up to an altitude of 2,000 m, which will not help much in rehabilitation of the degraded environment.

It is not possible to altogether prevent geological events like landslides but their frequency, scale and destructive potential can be limited by restricting human activity in the mid and high hills, ensuring proper environmental safeguards while undertaking construction of roads and other development projects and strictly enforcing building laws in vulnerable zones, besides   improving and expanding the forest cover.  The states should also give preference to construction of traffic tunnels while constructing roads instead of excavating hills over large stretches.

Major landslides in recent times

• 1968 —  A bridge was washed out in Maling landslide in Kinnaur which is still active
• 1982 — Sholding  Nullah landslide  caused collapse of bridge  
• 1989 — A landslide at Matiana in Shimla on Hindustan-Tibet road killed 40 persons 
• 1993 — Huge landslide damaged road and blocked the Sutlej
• 1995 – A massive landslide in Luggar-Bhatti area of Kullu district claimed over 100 lives.
• 2004 — Nine labourers were buried alive under a landslide at Mulgi bridge near Basantpur in Shimla 
• 2008 — A landslide at Nehru Kund near Manali killed six persons 
• 2015 — Falling rocks crushed 10 pilgrims in Manikaran in Kullu
• 2017— A sinking hill buried 46 people at Kotpuri near Paddar in Mandi