Landslide dams form when a landslide blocks a river, creating a natural barrier that can lead to the accumulation of water upstream. The Alaknanda River, in particular, is highly vulnerable to such natural dams in the Garhwal region, which could have serious consequences for downstream areas.
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According to a recent study conducted by IIT Roorkee researchers Alaknanda River flowing through the Garhwal region has been identified as most vulnerable to landslide-induced natural dams.
A landslide dam is a natural blockage in a river caused by a landslide, debris flow or rock avalanche. They can be formed by a number of factors including: Heavy rain, Earthquakes, Volcanic eruptions and Snowmelt.
Landslide dams can be very high and some are as tall as the largest artificial dams. They can pose a serious threat to lives and property downstream if they fail causing catastrophic outburst floods.
Some common causes of landslide dam failure include:
Overtopping: When the water level upstream exceeds the lowest point of the dam crest.
Seepage: A process that can lead to dam failure, especially when combined with overtopping.
Slope instability: Can cause failure.
Impact waves: Caused by mass movements into the lake or heavy rains.
The frequency and scale of landslide dam events has been increasing in recent years due to extreme climatic and geological hazards.
Some examples of landslide dams include:
The dams formed along short river reaches after the 1999 Chi-Chi earthquake, the 2004 Chuetsu earthquake and the 2008 Wenchuan earthquake.
The 18 landslide dams formed by the 2009 Morakot typhoon in Taiwan.
Tangjiashan Lake formed by the 2008 Sichuan earthquake.
Aspect |
Details |
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Main Tributary |
One of the two main tributaries of the Ganga (along with Bhagirathi River) |
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Origin |
Melting waters of the Satopanth and Bhagirath Kharak glaciers in the Garhwal Himalayas, Uttarakhand. |
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Major Confluences |
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Confluence Worship |
The confluences of these major tributaries are worshipped. |
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Ganga Formation |
The Alaknanda contributes more significantly to the Ganga's flow than the Bhagirathi at the time of formation |
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Pilgrimage Sites |
Badrinath, Hemkund Sahib, Joshimath, part of the Char Dham Yatra |
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Char Dham Yatra |
Includes Badrinath, Kedarnath, Gangotri, and Yamunotri, with Alaknanda being a significant part of the route |
READ ABOUT
Uttarakhand Winter Char Dham Tourism: Off-Season Pilgrimage
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PRACTICE QUESTION Q.Consider the following pairs regarding the tributaries of the Alaknanda River and their confluences (Prayags): Tributary Confluence (Prayag)
Which of the pairs given above are correctly matched? (a) 1 and 3 only (b) 2 and 4 only (c) 1, 3, and 4 only (d) 1, 2, 3 and 4 Answer: a Explanation: Vishnuprayag: Alaknanda meets Dhauliganga. Nandprayag: Alaknanda meets Nandakini (not Rudraprayag). Karnaprayag: Alaknanda meets Pindar. Rudraprayag: Alaknanda meets Mandakini (not Devprayag). Devprayag: Alaknanda meets Bhagirathi to form the Ganga. |
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