Garbyang: Sinking village of Higher Himalaya

Once upon a time, prior to Sino-Indian conflict of 1962, Garbyang was a thriving village located on Indo-Tibetan trade route. The village is presently facing serious land degradation, and interventions are required for retarding, and finally checking the pace of ground subsidence so as to secure the age-old legacy.

If not addressed timely continuing ground subsidence could disrupt strategically important Dharchula – Lipulekh motor road with serious national security implications.

तिब्बत से होने वाले व्यापार के बल पर कभी समृद्ध रहा गर्ब्यांग गांव आज काली नदी द्वारा निरंतरता में किये जा रहे कटाव के कारण भू- धंसाव की समस्या से ग्रस्त है जिसके कारण नेपाल सीमा पर बसे इस  गांव के ज्यादातर घर क्षतिग्रस्त हो चुके है और निराकरण के आभाव में काली नदी द्वारा किया जा रहा  कटाव तिब्बत (चीन) सीमा तक सहज पहुंच सुनिश्चित करने के उद्देश्य से बनायीं गयी  सामरिक महत्व की धारचूला – लिपुलेख मोटर रोड को बाधित कर सकता है।

Garbyang and the surroundings

Garbyang in Pithoragarh district of Uttarakhand province in India is located on the Indo-Nepal border along the left bank of Kali river that flows westward on a nearly flat surface after its confluence with Tinker river and exits the valley through a narrow outlet below Chia-lekh (lekh = pass in local parlance), which is the highest elevation (~ 3500  m) to  the west of Garbyang and separates lower Kali basin to the west from higher Kali basin towards  the east.

Unlike most Himalayan rivers Kali river cuts across the strike of country rocks like an antecedent river system and the drainage pattern of the area is largely controlled by structural configuration of the basin.

The valley housing Garbyang village trends NE-SW with flight of terraces carved on lacustrine sediments with the village located towards the northern flank of the valley, and Kali river flowing parallel to its southern flank. A steep ridge running parallel to the village in the north acts as an eyebrow and protects it from rockfall, landslide and avalanche. Being north-facing, the slopes around the village support scanty vegetation due to high rates of evapotranspiration.

Access to Garbyang

Until recently route to Garbyang was arduous and tiring wherein one had to negotiate steep ascent and decent many a times. This journey through Narayan Asram, Malpa, Budhi and Chia-lekh required almost two days of tiring trekking. This has now been eased by recently constructed Dharchula – Lipulekh motor road – thanks to the efforts put in by Border Roads Organisation.

Garbyang has a population of 426 (277 males and 149 females; Census of India, 2011) and during winters when the upper reaches experience heavy snowfall most people migrate to Dharchula.

Lacustrine deposits around Garbyang

The sedimentary sequence forming the flat surface in Garbyang valley is in fact a varve deposit – annual sedimentary or annually laminated layers deposited in the lake formed in the geological past by the damming of Kali river around Chia-lekh by the debris brought down by the glaciers of Mount Api (7132 m).

The Chia-lekh ridge, defining the distal end of this lake is geomorphic expression of the Tethyan Fault, along which high grade Central Crystalline rocks are juxtaposed against Tethyan sedimentary sequence to the north.

Layers of this sedimentary sequence are observed to be highly visible as the particles washed into the layers deposited during the summer season are relatively coarser due to greater flow strength, than those deposited later in the year during the winter season when the lake received limited or no inflow due to freezing of streams and rivers. This process resulted in a pair of layers — one coarse and one fine — for each annual cycle.

In fact varve deposits are amongst the smallest-scale events recognized in stratigraphic records. These at the same time provide important proxy records for reconstructing past climate and deciphering climate change trends. It is for this reason Garbyang has been a favourite destination of palaeo-climatologists, and a number of scientific publications provide graphic details of these deposits.

The relicts of the varve deposits start to appear just below Chia-lekh and continue north-northeast till Gunji for a distance of 11 km. These are presently terraced and run parallel to the valley. The degree of preservation is good towards the west while towards the central part and in the east these merge together.

The central part of the terraces is witnessing extensive slumping, and the axis of slumping coincides with concavity of the Kali meander that has been pushed towards north by colluvial  debris descending from the southern  mountain  range along an avalanche chute.

Withering legacy

Edwin T. Atkinson described a village Chhindu near Garbyang having washed off by the river. He in particular indicated the threat posed to the lower terraces due to toe erosion by Kali river.

The threat perceived by Edwin T. Atkinson was not a vague assessment. Continuing erosion by Kali river has actually destabilized the lacustrine sediments and the ground surface around Garbyang has consequently been broken into undulating terraces.

The central portion of the valley that houses Garbyang village is presently facing severe land subsidence. According to  the  villagers there were four  streets in  the village (situated at Terrace–1) aligned east – west parallel to the terrace. None of these streets exist at present and only a few house are left on this terrace.

Due to continuing ground movement all the streets have merged together resulting in shamble of houses put together in a basket. Except for a few houses on Terrace-1 that are located close to the hill over firm footing all other terraces in the central portion have merged together.

Together with downslope movement the area also shows signs of vertical subsidence. More than one floor of many houses have thus been consumed by this.

The rate of downslope movement as also vertical subsidence exhibit spatial variance, and some houses are observed to be distorted due to differential ground subsidence. Maximum displacement of around  20 m is delineated for some houses that have old reference  surfaces in their proximity.

Continuing ground movement has taken toll of most houses of Garbyang. Many have been consumed by sinking ground while hitherto adjacent ones are now placed at different levels.

Once prosperous village with magnificent houses thus lies in a dilapidated state. The villagers have moved out to nearby safe places and most of the exquisitely carved wooden panels have found their way across the Kali river in the Napalese territory.

Cause of ground instability

Observed fissures and cracks, as also distortion and buckling in the houses  represent response of these rigid  structures to the stresses generated by the  yielding  earth beneath them.

Even though some researchers attribute ground movement in Garbyang valley to be tectonic, the slip surfaces are observed to be disposed parallel to the valley wall and show ductile deformation features in clay rich layers while in upper boulder beds sharp detachment surfaces are observed. Lacking cohesion amongst constituent boulders and pebbles has resulted in sudden gravity driven movement along the detachment surfaces close to the surface.

One such prominent detachment surface is observed to run east–west for almost 150 m. Vertical displacement along this surface at the eastern end is around 4 m as delineated from the level of two houses earlier at the same level. However at the western end it shows displacement of around 20 m.

According to the masses movement along this surface coincided with M~6.5 earthquake of July 29, 1980 along Indo-Nepal border that is often referred to as Dharchula Earthuake. The detachment surface is still fresh but no shattered boulders are observed along this.

All deformation features observed in the varve deposits are produced  by north-northeastward gravity gliding along weak surfaces paralleling the valley walls that is driven by toe erosion by Kali river. Though generally gradual this movement has sometimes been sudden, and July 29, 1980 earthquake along Indo-Nepal border triggered one such sudden movement.

Vertical subsidence of ground observed prominently around the village is attributed to percolation of water through the ground fissures and detachment surfaces and consequent washing away of finer material.

Kali river that flows parallel to the trend of the terraces is continuously eroding the base of the varve deposits and therefore the mass is moving downslope towards south along weak surfaces paralleling the valley walls.

Administrative apathy

The administration has done literally nothing to check the ground movement. Even detailed geotechnical investigations have so far not been undertaken to prepare an outline of the strategy to retard the pace of ground movement.

Rather than mitigation, administration actually resorted to an easier alternative of relocating the people. The families affected early were thus allocated land for rehabilitation in Terai – Bhabhar region around Sitarganj in Udhamsingh Nagar district. This however amounts to alienation of these people from their culture.

This was however not the first instance of such an unfair deal. The trading communities of the frontier villages were earlier given tribal status after the disruption of the trade with Tibet  following the Sino-Indian conflict of 1962. This was however a poor and shortsighted substitute for their economic rehabilitation which had severe and lasting adverse impact on the economy of entire Kumaun–Garhwal region.

Enhanced pace of land degradation

It is informed by the local people that the pace of ground sinking has increased after the disruption of cross border trade with Tibet in 1962. It is important to note that the frontier villages traditionally thrived on trade with Tibet and after the disruption of trading activities people had no incentive to stay foot in these villages that still lack easy access to various civic amenities and utility services.

Though resumed in 1992 volume, commodities, modus operandi and profits attached to the the trade with Tibet have changed drastically and it ceases to have perceptible impact on the economy of the region.

Most families have at present migrated from the frontier villages including Garbyang and settled at different places taking up other economic activities. At present these people return to their villages after long interval of time mainly to fulfil customary ritualistic obligations.

There could thus be two possible reasons for observed fast pace of ground subsidence – (i) pace of ground movement could actually be accelerated due to neglected maintenance of the terraces, or (ii) people returning after  long intervals of time observe accumulated movement of considerable duration, and therefore perceive the movement rate as having enhanced.

Way forward

At present strategically important Dharchula – Lipulekh motor road that traverses through the varve deposits around Garbyang faces the risk of being disrupted by continuing ground movement. This provides  administration a valid reason to take up the issue of ground subsidence around Garbyang seriously.

Moreover the state at present has at its disposal financial resources under recently constituted State Disaster Mitigation Fund (SDMF) meant for various mitigation works including detailed geotechnical investigations, DPR preparation and restoration of the area degraded by mass movement.

For treating the landscape of the area around Garbyang and restoring cultural heritage of the people following measures are suggested:

(i) Detailed geotechnical investigations should be carried out in the area to prepare an elaborate restoration strategy with incorporation of advanced  restoration tools and techniques.

(ii) Debris rolling down along an avalanche chute on the southern slope across Kali river might further divert the flow of the river towards the concave meander and aggravate the pace of toe erosion. Adequately planned measures are therefore suggested for arresting the pace of mass wastage on the southern slopes across Kali river.

(iii) Embankment and other protective measures are suggested along the right bank of Kali river, particularly along the concave meander to arrest the pace of toe erosion, and thus to stabilise the mass further north.

(iv) Plantation of suitable varieties along the course of Kali river is suggested for bank stabilisation and retarding the pace of toe erosion.

(v) The middle slopes are undergoing subsidence together with gulley erosion. Terracing is suggested along these slopes to reduce the pace of mass wastage.

(vi) Light weight structures should be promoted in the area. To the extend possible wooden houses with sloping tin roofs or prefabricated structures should be constructed.

(vii) Avoidance is the best strategy for any slide prone area and therefore it is required that all anthropogenic activities be discontinued in the zones showing active subsidence. This would  provide opportunity for natural regenerative processes to stabilise the area.

(viii) Provision of diversion of water from the head of the slide through a network of diversion channels is a must. These channels would discourage water from entering the rupture surfaces and thus reduce the pace of weathering. This would provide natural forces opportunity to heal the cracks. Reduced percolation of water would check washing away of fines and pace of ground subsidence would thus be retarded.

(ix) The ground fissures should be dug out to the extent possible and filled with clay or other impervious material and compacted to reduce seepage of water and consequent washing away of fine particles. This would reduce the pace of ground sinking.

(x) In order to make the restoration work acceptable, successful and cost effective people’s participation should be ensured and to the extent possible traditional knowledge of the people should be utilised for making the restoration works viable and acceptable to the masses.

(xi) A network of meteorological observatories should be set up together with surveying instrumentation to monitor the pace of ground movement for both correlating the pace of movement with precipitation and assessing the efficacy of treatment works.

(xii) Non-land based economic activities need promotion in the villages so that the villagers are encouraged to allow restoration work to be carried out in their fields.

It needs to be remembered that neglecting the issue of ground subsidence around Garbyang amounts to compromising round the year operationally of the strategically important Dharchula – Lipulekh motor road which could have national security implications.