Why Kedarnath Happened

A scientific analysis of the reasons for the disaster that afflicted Uttarakhand, particularly the synagogue townsfolk. THE primary trigger for the Uttarakhand disaster sideline the really arduous rain during June 16-18 was the extremely unusual behaviour of the monsoon this year everywhere north India. The incessant, heavy rainfall everywhere three age, perhaps attended by a few cloudburst-type events (which cannot be confirmed), resulted in flash floods and associated landslides.The end all round in their wake has been huge tho the volumedst impaction has been at the synagogue town of Kedarnath, which was in the midst of the annual travel season, with tens of thousands of people thronging the town and the downstream piece on the Mandakini river . 1). Rainfall measurements for June 16 and 17 at the Dehradun station, of 220 millimetres and 370 mm respectively, indicate the severity of the rain during these long time in the region. Haridwar certain 107 mm and 218 mm of rainfall on the twain twenty-four hour periods. Uttarkashi received 122 mm and 207 mm.While Mukteshwar (altitude over 2,000 metres) received 237 mm and 183 mm respectively on June 17 and 18, Nainital on the same(p)(p) days received 176 mm and 170 mm. Though rainfall over a 24-hour end in different parts of Uttarakhand has grandly exceeded these figures in the past (on many another(prenominal) occasions preceding(prenominal) 450-500 mm and once even 900 mm at Rajpur near Dehradun), prolonged heavy rainfall for nearly three days over a large area is perhaps unprecedented, and the cumulative effect, intensify by geophysical, meteorological and environmental factors, may be the reason for the enormity of the disaster.More pertinently, these numbers do not give the actual duodecimal picture of the very heavy rainfall in the higher reaches of the Himalayas (supra 3,000 m) in Uttarakhand, where Kedarnath, Gangotri and Badrinath are regain and where the impact has been most severe. This is because the rain gauge send of the India Meteorological Department (IMD) are all located largely in the lower Himalayan reaches (below 2,000 m) and at that place are no stations in the higher reaches (above three hundred0 m). This is probably because bumpfall data is regarded as more most-valuable than detai conduct rainfall data in these regions.As a result, there is no proper estimate of the rainfall in the affected regions. unhoped-for advance What was peculiar ab knocked out(a)(p) the monsoon this year? On June 14, the monsoon front was located over eastern United Statesern India. In fact it was a trifle muddy compared with the principle progress of the front (Map 1a). But within a day (Map 1b), the front advanced sound crossways Uttar Pradesh and the western regions to cover the total untaught by June 15, exactly a month ahead of its normal date of July 15.While the IMD had forecast a rapid advance with the announcement that the monsoon would r ead Delhi primarily the normal scheduled date of June 30, its advance right across to the west just within a day was all told unexpected. This has never happened in the past, according to M. Rajeevan, Adviser in the Ministry of Earth Sciences (MoES). A scheme of west winds from the Arabian Sea had also been active during the same period and had covered Pakistan.It was a strong westerly brass, and Rajeevan noted that it was interchangeable to the system that stayed anchored over Pakistan in July 2010 and caused widespread flooding in Sindh, Punjab and Baluchistan. Of course, by July 2010 the south-west monsoon had covered entire India, but this time around the system had create in June itself. It was the interaction amidst the advantageously-formed low-pressure system of the south-west monsoon from east to west and the upper air westerly stadium running from north-west Rajasthan to the east that resulted in the heavy rainfall over Uttarakhand.In fact, the westerly system dragged the monsoon trough, which was anchored over Rajasthan and central India until then, towards the north across Haryana. A monsoon trough facilitates the sweat of rainfall- do low-pressure systems along its path. Its rapid movement northwards enabled the low-pressure system that was in the eastern part of the country to quickly traverse and locate itself over north-west India. harmonize to Rajeevan, while the phenomenon of the monsoon trough being dragged northwards by the advancing strong westerly trough is known to occur, the exact dynamics of interaction between the deuce systems is not well studied.Thus, as the press release of June 20 of the IMD noted, nor-west India became the zone of an unusual confluence of the dickens startes of the monsoonthe Arabian Sea branch and the Bay of Bengal branch. The geology and orography of the Himalayan regions of Uttarakhand and Himachal Pradesh resulted in the unprecedented impact in these two States. While the IMD had issued warni ngs of widespread severe rainfall in the region soon after the observation of the advancing monsoon systems, the scale of impact could not be anticipated.Geophysical dynamics The peculiarity of the monsoon apart, the other interesting motion is what geophysical dynamics channelled the major part of devastation along the Kedarnath vale and downstream of Kedarnath on the Mandakini. The region around Kedarnath is known to geologists to be devoted to landslides. This is also clear from an early 1882 Geological Survey of India photograph of Kedarnath (Picture 2), which shows that the temple site is located not far away from the snouts of two portion glaciers.David Petley, an expert on landslides at the Department of Geography at shorthorn University, United Kingdom, has analysed the calamitous event at Kedarnath on the basis of paintings from the remote-sensing airs of the Indian Space Research Organisation (ISRO) and the U. S. Landsat. He points out that the amount of detritus and rubble below the glacier on the left side of the 1882 picture suggests that loony withalns of sediment and junk from the upper reaches was active even then, and adds that the immerse incline that is visible would have aided rapid transportation.It should be borne in thinker that the geology is still roughly the same (Picture 3). It is evident from the post-event images of Kedarnath town around the temple that the commodious destruction was the result of largescale rubble carried by the huge spate of water from the upper reaches above the town. One of the compounding factors was that the wintry regions above Kedarnath had received fresh and excess light speedfall when heavy rainfall scoot the region (Pictures 4a & b), according to scientists of the National Remote Sensing midriff (NRSC) of ISRO.Rainwater, with higher temperature, falling on the snow must have led to heavy snow melt and this runoff would have added to the rainwater runoff, resulting in a huge water ex ecute that carried with it a huge detritus execute, which struck the town with enormous ferocity. The snow cover has, in fact, increase in general subsequent to the extreme rainfall and flooding events (the satellite image on May 28/June 1 shows less snow cover). jibe to the NRSC scientists, the detailed dynamics of water pass due to snow melt caused by rain, particularly when snowfall is in excess, and the hydrology of it are not well understood.The NRSC recently released excellent high-resolution pre-flood and post-flood images of the Kedarnath region (Pictures 5a & 5b) taken by ISROs remote-sensing satellites Cartosat-2A and Resourcesat-2. The NRSC, on the basis of remote-sensing images from Resourcesat-2, has carried out an inventory of the landslides that occurred between Kedarnath and Sonprayag, a distance of approximately 20 km on the Mandakini. According to the preliminary report, the study identified a total of 192 landslides in this Himalayan stretch (Picture 6). Ma ny landslides were triggered in the glacial regions in the mountains above Kedarnath.The large dust works from above were the result of these immense landslides. Double whammy Actually, for Kedarnath it was a double whammy. The extensive misuse caused to Kedarnath town can be seen distinctly in the post-flood image. Just as there was an unusual confluence of two monsoon streams up in the atmosphere, in the mountainous terrain around Kedarnath, too, there was a coincidental reinforcing of two massive debris flows from above, one from the north-western side of the Kedarnath temple and the other from the north-eastern side.Petley has analysed these images to arrive at a plausible scenario as to what caused the massive onslaught on the town, virtually flattening it. This flow cascaded further and caused heavy damage downstream as well. The NRSC scientists, too, in their analysis, have come roughly to the same general conclusion. According to Petley, the two different but reinforc ing events that caused the disaster were landslide-induced debris that came from the glaciated area in the north-east and a glacial-related flow that originated from the north-west glacier. From the images, one can distinctly identify the two flows.Petley, from his analysis of the images, the-cause -of-the-debris-flow-disaster-is-now -clear/), has inferred the following 1. The flow from the north-east came down the margin of the glacier and spread out to strike the town. 2. The north-west flow descended from the other glacier to meet the town. 3. While a large part of the flow from the north-west passed the town on its west side, a part also struck it directly. On the basis of the pattern of compensate of sediments and their nature, Petley concludes that the flow from the north-west occurred after the one from the north-east.According to him, the debris flow from the north-east was triggered by a large, 75 m wide, landslide caused by heavy rainfall high on the mountains, which the n came down the steep slope about 500 m, gathering the debris in its path. The flow was initially channelled into a narrow gully formed by the glacier and on exiting it the flow spread out in the floodplains before striking the town over a large area. The steepness of the slope would have given the debris enormous velocity when it struck the town. The total length traversed by this debris flow is estimated to be about 1,200 m.The event from the north-west was, however, quite different, points out Petley. The sleep with marked 1 in Picture 7 is a moraine, which had created a block for a basin to form, go awaying the water to build up in it as a pool or a lake. This is what the topical anesthetic people call the Chorabari Tal, to which, in fact, pilgrims trek a few kilometres along the west side of the valley to have a dip. The Chorabari glacier has been retreating constantly in modern times, and according to D. P. Dobhal of the Wadia Institute of Himalayan Geology, it has retreate d about 300 m since 1960. The effect of the retreat is to leave a moraine that can allow lakes to form, which can then collapse, pointed out Petley in an e-mail message to Frontline. In Kedarnath, this is exactly what happened. I am not sure when the lake basin formedit may not have been in modern timesbut this is a dangerous situation. Of equal concern is the trend towards more vivid rainfall, especially if this occurs early in the year (that is, during snowmelt), Petley added. Wall of water eyewitness accounts say a huge wall of water swept the Kedarnath town in a flash.The spot marked 2 shows that the moraine had been hurted by the promptly building up water because of heavy rainfall and the water overtopping the moraine wall. The breach led to the sudden release of the impounded water and resulted in a massive wall of water sweeping across the Kedarnath valley and the town and causing a huge flash flood. According to the NRSC scientists, this lake would have had a attainment of about 15 m, and the event was not exactly a glacial lake outburst flood (GLOF), which occurs when a dam or moraine wall is breached because of the curl pressure exerted by the stagnant glacial water and ice that it encloses.This was a case of lake flooding because of excessive rainfall and consequent overtopping of the moraine wall, which eventually breached. The flow was so huge and forceful that it overtopped the moraine on the other side of the glacier as well, at the spot marked 3, resulting in three flows one lamentable south-east to join the earlier debris flow from the north-east and enhancing it before turning southwards and striking the town. The third flow is a saucily channel that opened up, perhaps exploiting an existing old channel, because of the breach at spot 3. Heading down the slope towards the town at great velocity, it gathered sediment and debris en route and resulted in a muchwidened flow closer to Kedarnath. However, the bulk of the debris flow, as Pictu re 7 shows, moved southwards towards the town down the main channel on the south western side, which is the normal channel for glacial water flow. The spot marked 4 shows heavy erosion due to the flow in the area, suggesting that the flow must have carried a huge volume of water. According to Petley, this flow must have carried the many huge boulders and rocks seen in the post-flood image of the temple town.Closer to the town, the flow spread before striking. As a result, the debris and water flow moved to the east side of the town as well, engulfing the town from both sides. According to this picture supplied by Petley, which others too are in general agreement with, Kedarnath was first pounded by an earlier debris flow from the north-east, then a later pounding by the flow from the north-west. Petley suggests that the latter flow must have been more streamlined because of the preceding events and also because it struck the town from both the west and the east simultaneously.The i mage also shows a dark patch just above Kedarnath on the north-eastern side (to the right of the spot marked 5) suggesting the formation of a new depression, which could have turned into a small-sized lake because of the heavy rainfall. It is also practical that water built up in this new depression, which would have been substantial, overtopped it and hit the town from the eastern side, enhancing the effect of the runoff and debris flow from the north-eastern side, an tone that Petley has not considered. Downstream of Kedarnath, the flow remained contained within the channel.As a result, there was massive erosion of the banks of the Mandakini Further, smaller villages downstream were also severely damaged, and some(a) of them, such as Rambara, were totally destroyed ). The damage caused to the Kedarnath region and downstream villages by the natural destruction resulting from unusual meteorological and geophysical processes was doubtless greatly enhanced because of the general en vironmental degradation caused by the massive and unregulated influx of pilgrims year after year, the haphazard development fuelled by tourist traffic, and the unplanned and poor construction of buildings and roads.Given the vulnerability of the region, the town itself has come up in a very dangerous location, points out Petley. Therefore, how much of the destruction in this event was actually man-made is a moot question. Besides the challenges of disaster management on such a massive scale, the Uttarakhand floods have also thrown up a dish of scientific challenges in the detailed understanding of monsoon dynamics as well as in the geophysical processes of landslides and large-scale debris flow and the heavy damage they can inflict on life, property and the ecology of a region.