A recent study by IIT Roorkee researchers Shivani Joshi and Srikrishnan Siva Subramanian has highlighted the Alaknanda River as the most vulnerable river to landslide-induced natural dams in the Garhwal region of Uttarakhand. The study, titled ‘Landslide Dam Studies in Uttarakhand, India: Past, Present, and Future’, was published by Springer.
Key Findings of the Study:
- Alaknanda River: Identified as the most susceptible to natural dams caused by landslides.
- Other Vulnerable Rivers: Mandakini, Dhauliganga, and Bhagirathi rivers follow in terms of susceptibility.
Unique Topography of Uttarakhand:
- Uttarakhand’s narrow valleys and gorges make it highly prone to natural dams formed by landslides.
- These dams create upstream lakes that pose the risk of catastrophic events known as Landslide Lake Outburst Floods (LLOFs).
Impact of Climate Change:
- The study emphasizes that climate change has increased the frequency of landslide dams in the higher Himalayan region.
- Narrow valleys in the region significantly raise the likelihood of rivers being dammed.
Most Affected Areas:
- Chamoli District: Identified as the most affected by landslide dams.
- Other Affected Areas: Rudraprayag and Uttarkashi, both in the Garhwal region, are also significantly impacted.
- The study recalls the Gohna Tal incident in Chamoli, where a landslide dam formed in 1893 and breached in 1970, causing extensive downstream damage.
Historical Context of Landslide Dams:
- The study traces landslide dam formations in Uttarakhand back to the Last Glacial Maximum (LGM), which occurred between 29,000 and 19,000 years ago.
- Significant events have been recorded since the 19th century.
Role of Climate Change and Human Activities:
- Climate Change: Increased the occurrence of landslide dams in recent decades.
- Human Activities: Deforestation, road construction, and hydropower projects have exacerbated the problem.
Seasonal Trends:
- August is identified as the peak month for landslide dam events, coinciding with the monsoon rains.
Preparedness and Mitigation:
- Despite fewer major incidents since 2018, the study stresses the importance of preparedness for future risks.
- The unpredictability of dam stability, especially in narrow valleys, poses significant challenges for disaster management.
Triggers of Landslide Dams:
- Heavy rainfall and cloudbursts are identified as key triggers for landslide dams.
- Debris slides are the most common type of landslide causing river blockages in Uttarakhand.
Multiple-Choice Questions (MCQs):
1. Which river is identified as the most vulnerable to landslide-induced natural dams in Uttarakhand?
- A) Mandakini River
- B) Dhauliganga River
- C) Alaknanda River
- D) Bhagirathi River
- Answer: C) Alaknanda River
2. What is the primary risk posed by landslide-induced natural dams?
- A) Earthquakes
- B) Landslide Lake Outburst Floods (LLOFs)
- C) Tsunamis
- D) Deforestation
- Answer: B) Landslide Lake Outburst Floods (LLOFs)
3. Which district in Uttarakhand is most affected by landslide dams?
- A) Rudraprayag
- B) Uttarkashi
- C) Chamoli
- D) Nainital
- Answer: C) Chamoli
4. When did the catastrophic breach of Gohna Tal occur?
- A) 1893
- B) 1945
- C) 1970
- D) 1985
- Answer: C) 1970
5. What are the key triggers for landslide dams in Uttarakhand?
- A) Deforestation
- B) Heavy rainfall and cloudbursts
- C) Earthquakes
- D) Road construction
- Answer: B) Heavy rainfall and cloudbursts
6. What period does the Last Glacial Maximum (LGM) refer to?
- A) 19,000 to 10,000 years ago
- B) 29,000 to 19,000 years ago
- C) 50,000 to 40,000 years ago
- D) 100,000 to 80,000 years ago
- Answer: B) 29,000 to 19,000 years ago
7. Which human activities have exacerbated the occurrence of landslide dams in Uttarakhand?
- A) Mining
- B) Deforestation, road construction, and hydropower projects
- C) Urbanization
- D) Agriculture
- Answer: B) Deforestation, road construction, and hydropower projects