Extreme Hydro Hazards

Recent Events: Torrential rain in Ramban, J&K, caused casualties, infrastructure damage, and forced relocations due to cloudbursts, landslides, and flash floods.

Cloudburst Definition: Sudden, intense rainfall exceeding 10 cm per hour over approximately 10 km². Common in mountainous areas like the Himalayas due to orographic lift. Difficult to predict.

Cloudburst Causes: Orographic lift (warm air rising over mountains, cooling, and releasing moisture), monsoon dynamics (moisture-laden clouds from Bay of Bengal/Arabian Sea release rain in Himalayas).

Landslide Definition: Downward movement of rock, soil, or debris on a slope due to gravity. Increased by rainfall.

Landslide Causes: Natural factors (heavy rain, earthquakes) and human activities (deforestation, construction) weaken slopes. Geological factors like soil composition also contribute. Water adds weight, lowers strength and reduces friction, leading to landslides.

Landslide-Prone Areas in India: North East Himalaya, North West Himalaya, Western Ghats, Konkan hills, and Eastern Ghats.

Flash Flood Definition: Sudden rise in water levels during or after intense rainfall, typically within 6 hours.

Flash Flood Causes: Intense rainfall overwhelming drainage systems, rapid snowmelt, dam breaches, glacial lake outbursts, and urbanization increasing runoff.

Impact: Cloudbursts lead to flash floods and landslides. Flash floods are sudden and life-threatening. Landslides can crush and trap people, block roads, and cause waterbodies to flood.