Magazine / Geographical
30/07/2011 00:34
Geographical Falling rocks, rising waters Earlier this year, a deadly landslide hit the Hunza Valley in northern Pakistan, blocking a river and forming a lake so big it submerged towns and displaced thousands of people. Humaira Khan and colleagues at the Karakoram Research Institute in Gilgit, Pakistan, report
The cracks first started to appear in November 2002, when a 6.5-magnitude earthquake caused a fissure to open on the side of the Hunza Valley near the village of Attabad. A further quake on 8 October 2005, this one measuring 7.6 on the Richter scale, opened up the cracks even wider. And then, on 4 January, as snowstorms swept across the region, the cracks opened right up, and a twokilometre-long section of the mountainside slumped into the Hunza Valley. Numerous houses were buried, 20 people were killed and dozens more were injured. An estimated 1,400 people were rendered homeless in the landslide’s immediate aftermath. But the consequences of the rock fall were to extend far from the site of the landslide itself. The rock and debris spread out across the entire width of the valley, rising to a height of some 160 metres at the saddle and blocking both the Karakoram Highway – the only land link for vehicular traffic between Pakistan and China, and the main trade route between these two countries – and the Hunza River. As water piled up against the blockage, a lake formed upstream and the river dried up downstream. Large rocks continued to fall from the mountain tops for several weeks after the initial landslide. Meanwhile, the lake steadily grew, both in area and depth, eventually submerging the villages of Ayeenabad, Shishkat and Gulmit, and causing irreparable damage to property, agricultural land and valley-bottom forests. About 22 kilometres of the Karakoram Highway were inundated or otherwise severely damaged. On the downstream side of the slide, the Hunza River ran virtually dry, damaging both valley-bottom agriculture and the river’s fish. Four villages – Attabad Payeen, Attabad Bala, Sarat and Ayeenabad – were affected by the landslide in the initial phases, while about 20,000 people were cut off from the southern part of the Hunza Valley and the rest of the country. Inhabitants of Ahmadabad and Ayeenabad on the upstream side of the barrier were evacuated to escape the rising waters. The food and fuel needs of those trapped by the lake in extremely cold temperatures were initially met through a helicopter service run by the Pakistan Army and the Aga Khan Development Network. Later, boats began plying the lake, ferrying people, goods and even loaded trucks. Flooding fears As summer approached and temperatures rose, snow and glaciers located upstream from the lake began to melt, causing the lake to rise even further. It eventually spread to the villages of Shishkat, Gulmit, Hussaini and even Passu, about 25 kilometres upstream. As the lake continued to rise, a new, potentially even more devastating disaster loomed. In an early report, David http://www.geographical.co.uk/Magazine/Hunza_-_Dec_10.html?print=page
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Magazine / Geographical
30/07/2011 00:34
Petley, a landslide expert at Durham University, had pointed out that downstream communities were at great risk should the blockage give way suddenly. The resulting flash flood would affect anyone living within 60 metres of the original river level between Attabad and as far away as Tarbela. In order to counter this threat, in late April, a group of engineers from the Pakistan Army began to cut a spillway on the saddle from the mouth of the lake. When it was completed in mid-May, the spillway was 30 metres deep and 40 metres wide. Around this time, early-warning systems were established in Hunza, and more than 30,000 people were moved from both upstream and downstream communities. Closed-circuit cameras were installed near the spillway for 24-hour monitoring, and an FM radio station was set up in Hunza for warning threatened communities. The formation of the lake not only uprooted people and damaged their property but also destroyed their agriculture, fruit farming and social forestry. Upstream communities moved quickly to cut down thousands of willow and fruit trees in order to prevent them from being wasted. However, the rising waters inundated fields of potatoes, the main cash crop. Cherries, another important source of income in the downstream communities, suffered due to the lack of the required irrigation water and access to markets. Holding firm As of mid-October, the Attabad lake remains, and it looks as through it’s here to stay – or at least a large part of it is. The spillway has been letting lake water flow down into the valley, and the lake’s level is beginning to drop. Thankfully, even at a high rate of discharge down the spillway of more than 480 cubic metres per second, the dam has held, defying all early forecasts. The level of the lake has also decreased somewhat due to the onset of colder weather and the consequent reduction in river-water inflow. Plans are now in place to drain the lake further during winter by deepening the spillway by another 30 metres. ‘The task will be completed before the melting process of glaciers restarts,’ provincial finance minister Mohammad Ali Akhtar told The Express Tribune. Officials hope that this will enable the reopening of the all-important Karakoram Highway. The upstream communities, however, continue to suffer immensely, and need to be resettled as soon as possible in order for them to resume their working lives. Pakistan’s federal government has announced a 100-million-rupee (£726,000) relief package, and displaced people have been offered compensation, but there is much local resentment about the pace and scale of the relief efforts. In July, the Chinese government agreed to provide technical assistance, and large numbers of Chinese troops and contractors are now in the area, primarily to carry out work on the Karakoram Highway, but there has been little visible progress. Reports have emerged of disagreements between Pakistani officials and Chinese contractors over how to proceed. Hunza’s landslide history The mountains of the Hunza region were formed about 30 million years ago, when the Indian tectonic plate collided with the Eurasian plate. In geological terms, the mountains are young, and are still rising as the Indian plate continues to slide under the Eurasian plate. Consequently, the region is seismically active, with frequent earthquakes and tremors, and has a history of landslide dam bursts. In 1858, the Hunza River was blocked by a landslide in a location similar to January’s. Then, as now, a large lake formed, reaching a length of more than 20 kilometres and submerging Gulmit, Hussaini and Pasu villages before the dam broke, about six years later. The resulting flash flood was described in a contemporary report: ‘At 5am on August 10, 1858, the Indus at Atak (Attock) was very low; at 7am, it had risen ten feet; by half an hour after noon it had risen 50 feet, and it continued to rise until it stood 90 feet higher than in the morning.’ The speed of the rising flood waters drowned a colonial army that was camping on the bank of the Indus. Humaira Khan, Mehjabeen Abidi-Habib, Muzaffar-ud-din, Babar Khan and Richard Garstang December 2010 Disaster charity ShelterBox has been working to provide relief for those displaced by the landslide and lake in the Hunza Valley. Donations to support its work can be made at www.shelterbox.org
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