Frequent landslides in Uttarakhand worry scientists
Landslides are common in this Himalayan state of Uttarakhand, especially following heavy monsoon rains. But what has left scientists worried is increase in the number of such phenomena in recent yearsdehradun Updated: Jul 13, 2017 20:20 IST
Landslides are common in this Himalayan state of Uttarakhand, especially following heavy monsoon rains. But what has left scientists worried is increase in the number of such phenomena in recent years.
Over 5,300 people were killed in landslides since 2000 when the mountain state was formed. Besides rains, scientists blame weak top soil for frequent occurrence of landslides. Environmentalists, however, blame developmental activities and poor vegetation for this phenomena.
“Slope gradient and lithology (structure and composition of a rock formation) coupled with heavy rains triggers landslides,” said R Jayangondaperumal, a senior scientist with Wadia Institute of Himalayan Geology (WIHG). “The number of landslides are increasing in Uttarakhand. We have only engineering attempts to mitigate them,” he said.
Dehradun-based WIHG is an autonomous institute for the study of geology of the Himalaya under the central government.
Recently, the public works department (PWD) identified 39 zones across the state that are prone to landslides. Nine of these zones are being undertaken by the union roads and transport ministry for mitigation while the state PWD is working on 21 sites with funds from Asian Development Bank. The detailed project report of remaining 9 zones is underway.
To avoid landslides in these areas, various steps like gabion walls, wire mesh, rock bolting and other steps are taken depending on their location. Despite all these efforts, landslides - big or small - are reported every now and then.
A landslide in May on Badrinath route blocked movement of over 14,000 pilgrims.
According to the latest disaster management and mitigation centre (DMMC) report released on Thursday, Dharasu band between Rishikesh and Yamunotri -NH 94 is blocked due to landslide and Border Road Organisation (BRO) is working on it.
Dehradun district has reported blockage in 11 motor roads, particularly in remote Chakrata block. Forty roads are blocked in Pauri district, 5 in Tehri, Rishikesh-Badrinath highway in Lambagad is blocked while 25 roads are blocked in Chamoli, 11 in Nainital, 12 in Champawat, 6 in Almora and 10 in Pithoragarh, the DMMC report said.
“Certainly, the frequency of landslide occurrences has increased over the years. Heavy rainfall is the main cause which weakens the mountains and it’s a challenge for us. We are working to check these landslides through various methods,” Rakesh Purohit, chief engineer of the PWD, told Hindustan Times.
WIHG too has come up with landslide inventory in Bhagirathi Valley. The inventory was set up after the 2013 Kedarnath deluge that left over 5,000 people dead.
The Bhagirathi River originates from Gaumukh. The inventory analyses impact of the event on slope movements wherein new, reactivated, old and inactive landslides were reported using Resourcesat 2 Linear Imaging Self-Scanning sensor (LISS) IV satellite images.
A total of 2,772 landslides were mapped by the inventory. Of these 1,434 were classified as new landslides and 533 were reactivated while 451 were old.
A paper on geomorphology published in Science Elsevier in January 2017 highlights, “Landslides can happen when rainfall amount reaches over a particular threshold of 155, 212, or 290 mm making the slopes almost saturated.
“Landslides induced by extreme rainfall also depend on the initial water content (antecedent), geological local terrain settings and regional factors. This means that sudden landslides are mainly caused by rainfall extremes.”
The Uttarakhand government in August 2016 signed a memorandum of understanding with Japan International Cooperation Agency to study and mitigate landslides in the state.
Under this programme, three sites have been identified in Rudraprayag, Rishikesh and Nainital where Japanese method of restricting landslides would be adopted in coming years.
Activist Anil Kumar Joshi, known as Mountain Man, blames developmental activities behind this occurrence. “Road construction in vulnerable valley is main reason why it (landslide) is happening. No steps are taken to secure the sensitivity of mountains,” he said.
Others blame poor vegetation. “The vegetation in hills isn’t enough to hold the top soil which results in erosion,” said environmentalist Vikrant Tongad, who raised the issue of pollution by rafting and camping in white waters.
“The government must take immediate steps to plant trees with deep roots so that we could at least avoid this occurrence in coming years,” Tongad said.