Uttarakhand

• 08 Jan 2025

Landslide Dams in Uttarakhand

Why in News? 

A recent study by IIT Roorkee identified the Alaknanda River, flowing through the Garhwal region, as the most vulnerable to landslide-induced natural dams. The study is titled ‘Landslide Dam Studies in Uttarakhand, India: Past, Present, and Future’ and published by Springer. 

• It highlights that the Alaknanda is followed by the Mandakini, Dhauliganga, and Bhagirathi rivers in terms of susceptibility to such dams. 

 Key Points 

• Findings of the Study: 
  • Uttarakhand's Terrain: 
    • Uttarakhand’s narrow valleys and gorges make it highly vulnerable to landslide-induced natural dams, which block rivers and create upstream lakes. 
    • These blockages pose a significant risk of landslide lake outburst floods (LLOFs), which can have catastrophic consequences. 
  • Most Affected Areas: 
    • Chamoli, Rudraprayag and Uttarkashi, are the most affected by landslide dams. 
    • The breach of Gohna Tal in Chamoli remains the region’s most severe landslide dam incident, impacting areas downstream as far as Haridwar. 
  • Historical Context of Landslide Dams: 
    • Landslide dam formations in Uttarakhand trace back to the Last Glacial Maximum (LGM), between 29,000 and 19,000 years ago. 
    • Significant events of landslide damming have been recorded since the 19th century, with the most notable being the breach of Gohna Lake in 1970, which had long-term impacts. 
  • Current Trends and Concerns: 
    • The study indicates that the peak month for landslide dam events is August, coinciding with monsoon rains. 
    • Climate change, deforestation, road construction, and hydropower projects have exacerbated the frequency of such events in recent decades. 
  • Risk Mitigation and Preparedness: 
    • While there have been fewer major incidents since 2018, the study stresses the need for preparedness to mitigate future risks. 
    • The instability of landslide dams, especially in narrow valleys, poses significant challenges for disaster management. 
  • Key Triggers of Landslides: 
    • Heavy rainfall and cloudbursts are identified as major triggers of landslides. 
    • Debris slides are the most common type of landslide responsible for blocking rivers in Uttarakhand’s hills. 

 Alaknanda River 

• It is one of the headstreams of the Ganga. 
• It rises at the confluence and feet of the Satopanth and Bhagirath glaciers in Uttarakhand. 
• It meets the Bhagirathi River at Devprayag after which it is called the Ganga. 
• Its main tributaries are the Mandakini, Nandakini, and Pindar rivers. 
• The Alaknanda system drains parts of Chamoli, Tehri, and Pauri districts 
• The Hindu pilgrimage center of Badrinath and the natural spring Tapt Kund lie along the banks of the Alaknanda River. 

 Bhagirathi River 

• It is a turbulent Himalayan river of Uttarakhand, and one of the two headstreams of the Ganges. 
• The Bhagirathi rises at the foot of Gangotri Glacier, at Gaumukh, at an elevation of 3892m and fanning out into the 350 km wide Ganga delta, it finally empties into the Bay of Bengal. 
• The Bhagirathi and Alaknanda join at Devprayag in Garhwal and are thereafter known as the Ganges. 

 Dhauliganga 

• It originates from Vasudhara Tal, perhaps the largest glacial lake in Uttarakhand. 
• Dhauliganga is one of the important tributaries of Alaknanda, the other being the Nandakini, Pindar, Mandakini and Bhagirathi. 
• Dhauliganga is joined by the Rishiganga river at Raini.