Landslides threaten Himalayan communities as climate change intensifies

The Himalayas receive the majority of their annual rainfall during the monsoon season from June to September. Intense cloudbursts that occur suddenly and concentrate over a relatively small area, similar to a balloon bursting, characterize this period.

Climate change intensifies Himalayan rainfall events

Climate change is exacerbating these cloudbursts and other heavy rainfall events, making them more frequent and intense in the Himalayan foothills. This increased rainfall is causing the hilly slopes to become saturated and unstable more often, leading to an increase in rainfall-triggered landslides.

In 2023, from July to August, the Indian Himalayas, especially the northern state of Himachal Pradesh, witnessed an unprecedented number of cloudbursts that triggered thousands of devastating landslides.

According to the state’s disaster management authority, by the end of August, heavy rain and landslides had resulted in 509 deaths, destroyed at least 2,200 homes, and damaged an additional 10,000. The estimated losses for Himachal Pradesh during this period amount to US$1.2 billion. The majority of this destruction occurred during two brief periods in mid-July and mid-August.

The extent of the destruction caused to buildings, roads, and bridges is staggering. National and state roads have been eroded, a temple in Shimla collapsed resulting in 20 fatalities, and houses built on sloping ground were swept away by the rain. Even now, houses continue to slide downhill.

Monsoon intensification isolates Himalayan foothills

Damage has affected essential facilities like schools and hospitals, posing a continuous risk to lives. The bridge connecting a school in Kullu district to a town washed away, forcing the school to close for 52 days. Locals are living in tents with minimal amenities, which raises serious concerns about their safety with the onset of a cold and snowy winter.

In July 2023, four days of heavy rainfall led to landslides that blocked approximately 1,300 roads, including five national highways. This left the state virtually isolated from the rest of India. The impact was far-reaching with 1,255 bus routes suspended, 576 buses stranded, over 70,000 tourists evacuated, and people unable to access essential facilities and services. This hindered emergency response efforts, causing crucial delays in search and rescue operations as well as the delivery of aid.

While the summer monsoon and related cloudbursts are decreasing across India, they are significantly increasing in the Himalayan foothills. This is partly due to warm moist air rapidly lifting and cooling when it encounters the Himalayan barrier, forming large clouds that release their rain. With intense rainfall events becoming more frequent in the Himalayan foothills, it’s likely that the disastrous summer of 2023 could be repeated.

While climate change may be contributing to the increase in cloudbursts, landslides shouldn’t necessarily be a direct consequence of rainfall. However, human activities have made the Himalayas more susceptible to such disasters.

Human activities amplify Himalayan landslide risk

Deforestation in the region has removed tree roots that strengthen the ground and prevent soil erosion. Additionally, unplanned development and reckless construction have destabilized already fragile slopes.

Preliminary reports on this year’s landslides indicate that the most severe damages occurred along artificially cut slopes, where proper drainage and slope safety measures were lacking.

Both India and Nepal have constructed many hill roads haphazardly, which increases the likelihood of landslides during rainfall.

Outdated and often disregarded existing construction guidelines and building codes give little consideration to the relationship between urbanization and landslide risk.

One potential solution is to prevent rain from seeping into the ground, thereby maintaining the strength of the slopes. However, if soil absorption is completely prevented, surface runoff could lead to increased flooding downhill.

An engineering solution could involve placing an artificial soil layer above the natural soil to temporarily hold water during heavy rainfall, preventing it from seeping deeper into the slope. This “climate adaptive barrier layer” would then release water back into the atmosphere during a subsequent drying period.

The intensification of heavy rainfall makes it crucial for the Himalayas to implement new, reliable construction guidelines that consider climate change. Even though we can't completely avoid landslides, or immediately reverse global warming and the increase in cloudbursts, India should implement these preventive measures to help communities become more resilient to climate change.

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