Numerous survey reports and field studies clearly show the vulnerability of the region, both from climatic and geological point of view, and suggest that unplanned and uncontrolled infrastructure development would bring devastation. The recent sliding of Joshimath and other areas of Alaknanda valley is a glaring example of violation of environmental regulations and utter disregard of safety of the local residents by the government itself, writes Meenakshi Sarkar.
About two months ago, just after the Joshimath Disaster started making headlines, renowned geologist S. P. Sati commented – “The sad truth about Joshimath is, a major part of this town would be gone soon. Nothing can save it now”. Not only Joshimath, according to him, many other towns and settlements in Uttarakhand, like, Bhatwari, Dharchula, Munsiari, Gopeshwar, Karanprayag, Pauri, Tharali, and Nainital – may encounter a similar fate if no proper measures are taken immediately. All news reports and articles published after the Joshimath disaster are highlighting two key points – fragile geomorphology of the region and unplanned uncontrolled infrastructure development activities.
The geomorphology of an area means its geological setting and the terrain morphology. Being the youngest mountain chain, the Himalayas are still developing. This means that the entire mountain range is still moving along few thrust and fault zones. Geologists who study the Himalayas divide the region into four tectonic zones from south to north, separated by three such thrusts, one fault and one suture zone. The northernmost Indus-Tsangpo Suture zone separates the Himalayan units from rocks of Tibetan Plateau. The southernmost thrust known as Main Frontal thrust, separates the Indo-Gangetic plains from the Himalayan units. The thrust planes in between, from south to north are Main Boundary Thrust (MBT), Main Central thrusts (MCT) and the fault plane is South Tibetan Detachment (STD). The main mass of the Himalayas is getting squeezed between the MCT and STD (i.e. areas north of MCT) and being exposed as high mountain chains. As the state of Uttarakhand lies entirely in the active tectonic zone of Himalayas between MCT and STD, a major part of the state is prone to seismic activities.
A thrust is a geological dislocation feature, along which the older rocks slide up and lie over younger rocks. Due to this movement or ‘shear’, within a thrust zone, the rocks are intensely deformed and layered, hence they become much weaker. To understand this, consider the strength difference between a brick and a stack of floor tiles. It will take a strong blow of hammer to break a normal brick. But in the case of a stack of floor tiles, you can simply dislodge the stack and scatter the tiles with bare hands, though one single tile is actually as hard as the brick. Also, if you place a brick on the floor inclined to a wall, it would remain in a stable position. But if a stack of tiles is kept inclined, with time, or with little disturbance, individual tiles may slide over each other and the whole stack slips and falls. The basic difference in the behavior of a brick and the stack of tiles is the presence of a thin non-sticky layer (or the gap) in between the two pieces of tiles, which is geologically known as a ‘weak plane’. The rocks in the thrust zones are like a stack of tiles, full of weak planes, along which they can move or get dislodged if the delicate equilibrium of the rock, soil and groundwater is even slightly disturbed. Also these sheared rocks are more prone to weathering.
Places like Karanprayag, Bhatwari, Munsiari, Dharchula, Gopeshwar and Joshimath are located in a weak zone near or within the Main Central Thrust Zone, which is bounded by Munsiyari thrust at the bottom and Vaikrita thrust at the top. Rocks above the Vaikrita thrust are highly deformed gneisses and schists. Apart from these major weak zones, there are many other local fault or thrust planes, which have shown signs of reactivation in the recent past. Some of the towns like Nainital, Munsiari and Bhatwari are bounded by such local planes of weakness.
Many of the settlements in this region are situated over glacial and fluvial deposits or relict debris of past landslides that lies over the deformed fragile bedrocks. The town of Joshimath is built over a relict landslide, about 2000 years old. The stability of these recent sediments or debris depends on the equilibrium between the weight of the soil and pressure of water in the tiny pore spaces between soil grains. Normally these two opposing forces balance each other. But increased pore water pressure from glacial melting and erratic heavy rainfall due to recent climate changes have disturbed this delicate equilibrium and made the region even more vulnerable.
Sudden heavy rainfall and seismic reactivation of the fault planes may change the course of rivers causing flash floods and devastation on the banks. The rivers in upper stretches of the mountain have more eroding capacity than the rivers in planes. They usually have deep narrow gorges and carry huge amounts of sediments and debris. The course of the rivers and streams of the area are controlled by the type and structure of rocks as well as climatic fluctuation. These rivers also preserve ancient terraces from earlier cycles of erosion and deposition. For example, Bhatwari is situated on the depositional terrace of Bhagirathi, whereas Dharchula is situated on the bank of Kali River. Like the relict slides, these depositional terraces are also prone to lose stability with change in overburden and pore-water pressure.
Numerous survey reports and field studies clearly show the vulnerability of the region, both from climatic and geological point of view, and suggest that uncontrolled development would cause devastation. These reports, written either from academic interest or for industrial or development purposes are available in the public domain. The development activity in the hills of Uttarakhand can extend from construction of RCC structure for residential use or step cultivation in fragile slopes to building of hotel, quarry, army camps, highways, dams and hydro-power projects.
Nainital is a perfect example that illustrates the problem of unplanned urban development. After British explorers discovered the scenic beauty of Naini and other lakes in 1841, it quickly became a hill station of about seven thousand people in 1901. By 2015, the resident population of Nainital was about fifty thousand, with a floating population of 1.5 lakh during peak tourist season. This town lies between MBT and Ramgarh Thrust, with several other fault lines crisscrossing the area. The rocks underlying the region are weak, mostly fractured limestone and shale that are prone to rapid weathering. Many landslides of variable magnitude have affected the town since its early days, with most notable ones in 1867, 1880, 1898, 1924 and 1998. A large part of today’s town is built on relict landslide debris, with some constructions on debris of recent landslides. According to the Earthquake zonation map of India, Nainital falls under second highest category – zone IV, which is also called High Damage Risk Zone.
In the recent past there was no large landslide or earthquake. But the area in and around Nainital has witnessed cases of small slides and creep (slow continuous movement of hill slopes). In 2018, cracks appeared in about a stretch of 25 m in Mall road near the lake, and part of the road caved into the lake. More cracks developed in Upper Mall road In January 2019. A landslide occurred by the lake at Thandi Sadak, on the opposite side of the Mall road; mud and boulders fell into the lake. And all these happened, even after a team of experts from IIT Roorkee warned about a highly fragile patch of slope at about 200mt above the Mall road in 2017. Baliyanala area which is a few kilometers away from the town witnessed a landslide in September 2018. The cause of this slide is identified as weakening of the slope by sudden discharge of subsurface water. The High Court also noted the fragility of the Nainital area in response to a petition filed by a resident of Nainital – Syed Nadim Khurshid, asking the administration for an issue of directions on the land stability. In January 2019, Irrigation department allotted Rs 44 crore in a project to stop landslides. In March 2019, 65 structures, including two schools, had been shifted to safer places.
In the past few decades, the climate crisis has induced erratic rainfall patterns, which has led to either water scarcity or water logging in the town. Urbanization and uncontrolled constructions has exacerbated this problem by affecting the lake that serves as drinking water reservoirs for the town. The lake, now partially filled up because of increased sedimentation, holds much less water and this causes drinking water shortage in the town. Sukha Tal – a seasonal lake, located 50mt above Naini Lake – is responsible for almost 53% of Naini’s total water recharge. In the past few decades, residential areas built in the lakebed have encroached the recharge area. In addition, installation of pumps during monsoon to stop flooding the Sukha Tal area, has greatly reduced its recharge capacity. A study carried out by the Centre for Ecology Development and Research (CEDAR) in collaboration with University of Cambridge, from 2014 to 2016 showed that between 2000 and 2016, the water level of Naini lake had reached zero level (a mark from which the depth of the lake is measured) almost 15 times, while in previous decade only twice water level went below zero level. Before, the lake had zero level water only during peak summer. But lately zero level is reached in January, and each year is setting a new record for the lowest water level.
On the other extreme, during heavy monsoon rain, water logging of the town is another problem faced in recent times. The drainage system of the town is over 100 years old, built in the colonial era. It is about 79 km long in the form of nullah and canals. Instead of repairing and improving this drainage system, newly constructed hotels and buildings were allowed to encroach on canals. Though the Nainital town has been divided in three zones – safe, prohibited and dangerous – in the last few decades, most of the new constructions took place in the prohibited and dangerous zones aggravating the situation. In 2012, Ajay Sing Rawat, an environmentalist, filed a petition to stop the encroachment of the drainage nullahs. As a result, in 2014-15, many houses and hotels were forced by the high court to move. Yet, according to a report in Times of India in July 2015, a sudden rainfall of 388 mm in a few days span had completely submerged the Mall road “… taking the administration completely by surprise” and creating almost 30 ft of debris at places.
Interestingly, the report of the Ramsay commission in 1880, the recommendations in a blog in 2016 by a professor of Garhwal University, and environmentalist Ajay S Rawat’s interview with TOI in March 2022 discuss the same problems and the same probable solutions. The Ramsay Commission advised implementation of proper drainage system, prohibition on construction and quarrying on the slope, planned forestation of steep slopes and finally appointment of “an honest, efficient and trustworthy officer” as an in-charge. The 2016 blog suggested proper risk-zone mapping, urban land use policy, proper framework for conservation of water source and finally a government plan to tackle the effects of changing climate. In Ajay Rawat’s opinion, deforestation, improper water harvesting, forest fire causing accelerated erosion and huge influx of tourists in summer are the main causes of the water and landslide crisis of Nainital. All these committee reports, petitions, court directives, government projects actually had little effect on the critical state of this lake and the surrounding area according to two newspaper reports published in 2022. Hindustan Times in August 2022 reported that there have been frequent small slides in the Baliyanala area since 2018, and each of them is closer to the residential area than the previous one. Another report published in TOI in September 2022 states: “The water level in Nainital’s Naini Lake, a key source of water in the town, has been recorded at 2,566 mm (or 8.4 feet). According to the irrigation department, this was the lowest recorded water level in the lake for the month of September”. The agreement among various reports clearly shows that things have not changed much in Nainital and the fragile ecosystem of the town has become even more unstable with time.
If the case of Nainital involves the indifference of the locals and inaction of the authorities, the sliding of Joshimath and other areas of Alaknanda valley is a glaring example of violation of environmental regulations and utter disregard of safety of the local residents by the government itself. The creep or sliding problem around Joshimath is decades old.
(to be continued)
( The author is a freelance field geologist and avid traveller)
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