Heavy rains in Hilly areas

Why in news?

Over the past few days, Dehradun and several other districts in Uttarakhand have experienced very heavy rainfall, triggering landslides in multiple areas.

• Cloudbursts - It is an extremely high amount of precipitation in a short span of time.
• It is a localised but intense rainfall activity that can cause widespread destruction, especially in hilly regions.

To know more about cloudburst, click here

• Reasons for heavy rainfall in Himalayan region -
  • Geographical location - The Himalayas lie at the intersection of moist tropical monsoon winds and mid-latitude westerlies, creating strong uplift and instability have experienced very heavy rainfall.
  • Unstable terrain - These areas naturally have steep slopes, inherently more susceptible to gravitational movement of rock, debris, or soil.
  • Tectonic Activity - These zones are often young, fractured, and highly weathered, making them structurally weaker and more prone to failure during intense rainfall or seismic activity.
  • Low-pressure systems - The consecutive rain-bearing low-pressure systems formed in the Bay of Bengal have travelled farther north than normal, causing intense rainfall in the region.
  • Atmospheric conditions – It can help the air rise swiftly, which leads to the formation of massive clouds and cause higher-than-normal precipitation locally over the hilly region.
  • Monsoon climate - The Himalayan region experiences heavy monsoon rains during the summer months.
  • Population density - The Himalayan region is densely populated, with communities living in valleys.
  • Anthropogenic activities – Like constructions on unstable slopes, disrupting natural drainage systems, deforestation, rapid urbanization, etc leading to destabilising the terrain.
• Vulnerable to disasters – The hilly regions more vulnerable to disasters such as -
  • Flash floods and cloudbursts - Caused by intense rainfall over the mountainous terrain, leading to debris-filled torrents that sweep away infrastructure and cause loss of life.
  • Landslides - Often triggered by heavy rainfall and soil instability, exacerbated by deforestation and unscientific construction.
  • Subsidence - Events like the sinking of Joshimath are linked to factors like unmanaged tunneling and construction in fragile hill slopes.
  • Glacial Lake Outburst Floods (GLOFs) - Melting glaciers can create large lakes, and the sudden breach of their natural dams can lead to devastating floods downstream.
• Role of climate change –
  • Shifting of weather system - The southward shift of western disturbances and their interaction with massive southwest monsoonal systems creates complexity to rainfall prediction.
  • Global warming - Meteorologists warn that extreme rainfall events will become more common in the future due to climate change, particularly in hilly regions.
  • Arctic sea ice melting – It could represent yet another factor in this deepening mystery of monsoon variations in the hills.

Reference

Indian Express | Heavy rainfall in hilly areas