News: A cloudburst led to flash floods in the high altitude villages of Uttarkashi, killing four people, leaving at least 60 people missing.
About Flash Floods and Cloudbursts
- A flash flood occurs when an overwhelming quantity of water rushes into an area over a very short time – often within minutes or hours of intense rainfall.
- In some cases, they are triggered by sudden dam breaches or obstructions in rivers giving way.
- Features
- Unlike regular floods that rise gradually, flash floods strike swiftly and with force.
- Water levels can rise in under 30 minutes, catching people off guard and leaving little time to evacuate.
- Common causes of flash floods include:
- Intense rainfall over a short duration
- Steep slopes that rapidly channel water downhill
- Urban drainage systems that prevent water absorption
- Dry or hardened ground, especially after drought or wildfires
- Sudden release of blocked water or dam breaches
- Past examples
- India – 2013, Uttarakhand disaster where flash floods, triggered by melting glaciers and torrential rain, left thousands dead or missing.
- Spain – 2018, a flash flood in Majorca, Spain, turned streets into rivers within an hour, killing more than a dozen people.
- Germany – 2021, floods in Germany washed away entire villages after days of relentless rain overwhelmed rivers and reservoirs.
About Cloudbursts
- A cloudburst refers to an extreme amount of rain falling in a very short duration over a limited geographical area, typically less than 20-25 kilometres.
- The India Meteorological Department (IMD) defines a cloudburst as rainfall exceeding 100 mm per hour over a small region.
- Cloudbursts often occur in mountainous regions like Himachal Pradesh, Uttarakhand, or Jammu and Kashmir.
- Reason: It is due to orographic lift i.e. when moist air rises rapidly due to terrain and cools quickly, releasing massive rainfall.
Relation between Flash floods and Cloudbursts
- Cloudbursts can trigger flash floods, especially in hilly terrain, but they are not the same.
- A cloudburst refers to the rainfall event, while a flash flood refers to the result – the sudden overflow of water.
- One can occur without the other.
