Why in the News?
- A cloudburst in Uttarkashi, Uttarakhand caused landslides, disrupted key pilgrimage routes, and left several workers missing.
- Districts prone to flash floods and landslides have been placed on high alert.
Key Points:
About Cloudburst:
⇒ A cloudburst is a sudden, intense rainstorm that results in more than 10 cm of rain in less than an hour over a small area (approximately 10 km²).
⇒ It can also be accompanied by hail and thunder.
⇒ Cloudbursts are common in mountainous areas, especially in the Himalayas.
⇒ Due to their localised nature, cloudbursts are hard to predict or detect but can unleash sudden, devastating rainfall, leading to flash floods and landslides.
Landslide:
- Definition:
- A landslide is the downward movement of rock, soil, or debris on a slope due to gravity.
- It is a form of mass wasting, where earth materials move down a slope under the influence of gravity.
- Causes:
- Natural factors like heavy rainfall, earthquakes, and water seepage weaken slopes, while human activities such as deforestation and construction increase risks.
- Geological factors, such as soil composition and terrain, also affect slope stability and can lead to landslides.
Flash Floods:
- Definition:
- Flash floods are sudden increases in water levels during or immediately after intense rainfall.
- They are highly localized and short-lived events, typically occurring within 6 hours of rainfall.
- Causes:
- Flash floods are primarily caused by intense rainfall that overwhelms the soil’s absorption capacity and drainage systems.
- Apart from heavy rain, flash floods can also result from rapid snowmelt due to sudden temperature rise, dam or levee breaches, ice or debris jams, and sudden glacial lake outbursts.
- Additionally, urbanisation with impervious surfaces like roads and buildings increases runoff, reducing water absorption and intensifying flood risks.