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Three landslides, one after the other hit Shimla recently, leaving dozens dead and several grievously injured in their wake. These landslides are among the 113 that have ravaged Himachal Pradesh within just 55 days- roughly six times more than the previous year, as there were only 117 major landslides recorded in all of 2022 compared to only 16 in 2020. Himachal Pradesh has now been designated a “natural calamity affected area” by the state government.
These landslides have been triggered by the extremely high rainfall that the region has been receiving this monsoon. An alert has been issued in the region as heavy rainfall is expected over the next few days. The India Meteorological Department (IMD) has forecast isolated spells of heavy rainfall with thundershowers and moderate rainfall in a few spots in Shimla, Solan, Mandi, Chamba, and the surrounding areas.
All 12 districts classified as landslide-prone:
All twelve of Himachal Pradesh’s districts are at risk for landslides, according to the Landslide Atlas of India created by the National Remote Sensing Centre, ISRO, Hyderabad.
The majority of Himachal Pradesh, covering an area of more than 38,000 square kilometres, is classified as being in the “high” hazard zone by the National Institute of Disaster Management (NIDM), which also includes areas that are among the second most prone to landslides. The most vulnerable “very high to severe” landslide hazard zone covers a smaller area, roughly 7,800 sq km.
The image below shows the landslide zones of India as per NDMA report. It is important to note that Northwest and Northeast Himalayas and the Western Ghats are the two regions of high vulnerability, prone to landslides.
Can Climate Change be held responsible?
Experts are saying that climate change has a definite role in increasing the intensity of rainfall.
Madhavan Rajeevan, former secretary, Ministry of Earth Sciences, said, “The message is clear: the monsoon is becoming more variable. Increased variability means more extreme weather and dry spells. What we’re witnessing now aligns with the studies on the impact of climate change on the Indian monsoon.”
According to a veteran meteorologist Dr Ashok Deoras, “the probability of an ordinary rainfall event intensifying into a heavy or extremely heavy one will increase because of global warming.”
The triggers:
Himachal Pradesh has historically had a high risk of landslides during the monsoon. Over time, human activity such as deforestation, road construction, terracing, and changes in agricultural practices that require more intensive irrigation have greatly increased the vulnerability of the steeply sloping, geologically young, and unstable Himalayan ranges.
The unusual shift of monsoon trough
As per the information given by IMD, “The monsoon trough is expected to shift northward towards north of its normal position.” It is predicted that most of India is going to witness a break in the monsoon from the middle of the third week of August. However, the hilly regions of Himachal Pradesh and Uttarakhand which are battered by rains, could be prone to another wet spell.
Increase in rainfall intensity
According to a study, Climate change can affect the intensity and frequency of precipitation. Oceans that are warmer cause more water to evaporate into the atmosphere. More intense precipitation, such as heavier rain and snowstorms, can result from more moisture-laden air moving over land or converging into a storm system.
Overtourism
The flourishing tourism economy in Shimla has led to many houses being converted into hotels. The NIDM document states that the state’s authorities and the Tourism Ministry have actively encouraged this, turning a blind eye to the potential risks of such unchecked development. Notably, the document says such disasters cannot be ruled out in the future.
Construction work
According to geological expert Prof. Virender Singh Dhar, the main causes of the increase in landslides are the extensive cutting of hill slopes for construction and road widening, blasting for tunnels, and hydro projects. He added that Himachal had seen vertical mountain cutting for road construction with only 5 to 10 foot retaining walls.
According to experts, the state of Himachal’s slopes have become extremely vulnerable to landslides as a result of rock-cutting at the foothills and a poor drainage system, and heavy rainfall is making matters worse.
Mitigation Measures:
To reduce the impact of landslides NDMA has specified certain guidelines:
- Early warning system (EWS) and development of low cost landslide monitoring methods
- Involvement of Artificial Intelligence in monitoring
- Training program on landslide mitigation and DPR preparation
- Collaboration with local administration
- Public awareness generation and landslide strategy
References:
https://indianexpress.com/article/explained/landslide-himachal-old-story-8898739/
https://ndma.gov.in/index.php/Natural-Hazards/Landslide
https://www.epa.gov/climate-indicators/climate-change-indicators-heavy-precipitation
