Editorial 1: Topography, climate change: Behind heavy rains in Himalayas
Context:
The Himalayan region has increasingly witnessed episodes of extreme rainfall leading to flash floods, landslides, and significant destruction. The recent spell of intense rainfall once again highlights the interplay between the unique topography of the Himalayas and the impacts of climate change, which together make the region highly vulnerable.
Reasons for high rainfall in Hilly regions:
- The Himalayas act as a massive barrier for the southwest monsoon winds. When moisture-laden winds strike the mountains, they rise, cool, and release rainfall.
- Unlike the plains where rainfall is more spread out, the steep mountain slopes cause sudden and concentrated downpours.
- Such rainfall patterns often lead to cloudbursts, flash floods, and landslides, especially in narrow valleys and river basins.
- In recent years, the monsoon system has shown greater variability. Traditionally, monsoon rains are evenly distributed over the June-September season, but now heavy rainfall often comes in a few intense bursts.
- These cloudbursts and extreme spells are devastating in fragile mountain terrains.
- This year, during the south-west monsoon season from June to September, the region has received more than 30% surplus rainfall.
- During this time, the low-pressure systems formed in Bay of Bengal- have travelled north than normal, causing intense rainfall in the region.
Topographic, Geographic and Geologic Vulnerabilities:
- The Himalayan terrain is young and unstable, made up of fragile rock formations. Its steep slopes, narrow river valleys, and ongoing tectonic activity make it prone to landslides.
- These landslides are triggered due to the mud, loose soil, grave, and all materials which the descending rainwater carries along with itself.
- Roads, dams, and hydropower projects have further destabilized slopes, reducing their natural resilience.
- But in the plain areas such rainfall drains out into locally available water sources or into rivers.
- Urbanization and haphazard construction along riverbanks, combined with deforestation, increase the risk of flooding. Rivers like the Beas, Sutlej, and Chenab swell rapidly when intense rains occur, causing destruction downstream.
- The gushing water, mudslides or landslides from these swollen rivers force enters the human settlements cutting across roads, bridges.
- Thus, while the Himalayas naturally experience intense rainfall, anthropogenic interventions magnify the disasters.
Role of Climate Change:
- There has been the observation that large—scale weather systems have shifted downwards. The western disturbances have shifted downwards.
- Western Disturbances are moisture laden eastward-propagating wind bands that cause precipitation in the form of snow or rain along their route. These winds originate in the Mediterranean Sea that has a pronounced impact on India particularly during winter months.
- The southward shifting if Western Disturbances and their interaction with South-West monsoon system is creating complexity to rainfall prediction over the Himalayas.
- Global warming is the main reason for southward movement of these winds.
- Such extreme rainfall events may increase in the near future, particularly in hilly areas.
- Arctic sea ice melting may further increase the monsoon variations in the hilly areas.
Way Forward:
- The heavy rains in the Himalayas are not isolated incidents but outcomes of a dangerous interplay between topography, fragile geology, and human-induced climate change.
- While the region’s unique geography makes it inherently vulnerable, unplanned development and rising temperatures worsen the impact.
- To reduce risks, India must adopt sustainable development practices, integrate climate resilience into policies, and strengthen early warning and disaster preparedness.
- The Himalayan experience is a stark reminder of the costs of ignoring climate realities and the urgent need to act before disasters become more unmanageable.