Landslide Dam Threatens Zanskar Valley

It was the summer of 1975; we were working in the Kurghiakh Chu valley of Zanskar mountain ranges. We were looking for evidences of environment during the pre-history in the Paleozoic and Mesozoic Eras of the Earth’s history. In the trail of some interesting fossils we shifted from the Kurghiakh Chu to Phuktal River (also called Tsarap River) valley. Our passage was along the river at a height of about 50m above the river. The roar of Phuktal was mightier than Kurghiakh because the valley was narrow here. The roar of water created different impressions in our minds. To me it sounded like the hurrahs of the victorious soldiers returning home, while my friend thought that it sounded like several helicopters hovering over us! We were following our mule train, suddenly it stopped. On enquiring, we were told that mules can’t go beyond this point because the path beyond that was made of long rectangular pieces of rocks embedded on a vertical cliff, like stairs sans railings. At places some of the pieces were missing so one had to jump carefully, a slight misjudgement, and one could land in the roaring torrent below! We had no option but to carefully negotiate the ‘stairs’.

At the base, one reached a comparatively wider bank and after walking a few steps back upstream along the river there was a terrace wide enough to accommodate our three tents. Our muleteers were pretty good at such times. They brought all the equipment on their head loads and we pitched camp.

Across the Phuktal, on the cliff was the mighty Phuktal Gompha. The approach to which, was through a rope bridge. Several ropes were held together to make a thick rope of about six inch diameter. This rope was stretched across the river. It sagged in the middle and one could see the wet part of the rope, where water splashed on it constantly. Two parallel strings like ropes ran about two feet above the thick rope. These parallel ropes were held in position by cross ropes connected to the thick rope. To walk on this rope bridge, one had to put foot across and hold the string like ropes to maintain balance. As one walked the thick rope swayed. In the middle of the river one spray of water was enough to drench our jeans. One could easily lose the foot or hand hold. God knows how I crossed the bridge, just to see the Gompha.

On the steep climb to Gompha we saw pockets of clay in the rocks, suggesting that the stream had been blocked in the past and the blockade must have remained like that for few years to let the clay accumulate.

In such terrains the atmospheric agencies hammer the rocks and weather them pretty fast. There are no trees to save the rocks or hold the mountain slopes. The Nature seems challenge the mountain, ‘I am the supreme power here, let me see if trees or man can save you!’ Indeed, at such places the Nature wins. Though at other places too it is the Nature only that wins, but we do try to subvert its designs. The weathered rocks develop cracks and crevices, which often get filled with water or frost. As the Sun shines, the water frozen in the cracks melts and expands, causing explosive ruptures at times. The rock bursts open with a loud bang. The loose material thus produced, lies on the steep slope till it is not disturbed. Year after year, the weathered product is added, leading to scree slopes. Anything that can disturb this material like heavy snow, rain, minor earthquake or erosion at the base by the river can lead to mass movement down the slope. At times such movements are powerful enough to dam the River.

On 31 December, 2014, exactly this is what has happened. Phuktal stream has been blocked and an earthen dam about 600 meters long has been created says David Petley, an expert on landslides. Petley’s report in his blog is based upon the analysis of satellite imageries from CartoSat-2 collected by the Indian Space research Organisation (ISRO). The blockade by debris is about 200 meter high and the lake formed behind, as a consequence covers approximately 55 Hectare area in a stretch if about eight kilometres, says Petley.

It is to be noted that the point where the river has been blocked is at the junction of nala draining in to Phuktal stream. The River at this juncture takes a northwest to southwest turn. In this area the frost and ice action produces plenty of fine grained rock powder, and the water flowing underneath this cover makes the whole mass move down the slope. Geomorphologically, the slopes are steep here.

Of late the area downstream also known as the ‘chadar’ trek has become a tourist’s paradise, because the river is frozen and the visitors find it exciting to walk/skate/slide on the frozen stream. As a precaution the trek has been closed and people prohibited visiting the area. There are about 29 villages downstream. As in the case of Gohna landslide of 1897 when the British Government, after getting the approximate date of a possible dam burst by the Geological Survey of India, got the entire area from Gohna to Rishikesh in now Uttarakhand. The dam did burst, albeit partially on the speculated date in August 1898. As result of precaution only five people at Srinagar died in the flash floods caused by the dam burst on Birehi Ganga.

It is time for the concerned district authorities to awaken from hibernation and move the villagers, if required by force to safer areas. Once the summers are set the volume of water in the artificial reservoir will be beyond imagination and the wrath of the Phuktal may be tremendous. Meanwhile techniques of controlled blasting can be used to gradually dismantle the artificial dam. Of course at present the area is not easily negotiable, but yet it is not inaccessible.

Yet another point to be noted is that this dam if it bursts, which it will someday, it will not only play havoc but also ruin the Nimoo-Bazgo and Alchi hydroelectric projects, further downstream.


More by :  V. K. Joshi (Bijji)

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