Why in news?
A sudden cloudburst over Uttarakhand’s Dharali region on 6 August 2025 caused flash floods and landslides, sweeping away houses and claiming at least four lives. The event renewed attention on extreme rainfall episodes in the Himalayas.
What is a cloudburst?
A cloudburst is an intense burst of rainfall over a very small area in a very short time. The Indian Meteorological Department earlier considered rainfall greater than 100 mm in an hour over 20–30 km2 to be a cloudburst. Research in 2023 suggested redefining it as 100–250 mm of rain within an hour over just one square kilometre. Such events usually involve towering cumulonimbus clouds, orographic lifting of moist air and sudden release of trapped moisture.
Why are hilly areas more prone?
- Topography – steep slopes encourage rapid runoff. Water accelerates down these slopes and cannot infiltrate, so streams become torrents.
- Orographic lift – moist monsoon winds are forced upwards by mountains, cooling quickly and releasing rain.
- Rocky terrain – thin soils and exposed rock limit absorption, causing rain to collect on the surface.
- High altitudes – settlements often cluster in narrow valleys where any excess water becomes dangerous.
Historical cloudburst disasters
India has seen several tragic cloudbursts: Hyderabad’s Musi River flood of 1908 killed thousands; in 1970 a cloudburst on the Alaknanda River caused mass casualties in Uttarakhand; in 2010 a cloudburst in Ladakh’s Leh region left 179 dead and many injured. In the last few years there have been multiple cloudburst‑triggered disasters in Uttarakhand and Himachal Pradesh.
Mechanism and climate link
- Rapid condensation: Strong updrafts in a storm hold huge amounts of moisture. When these currents collapse, the entire water column falls suddenly, causing catastrophic rainfall.
- Climate change influence: Warmer air can hold more moisture. A warmer Himalaya allows more water vapour to accumulate before releasing it in a short burst.
- Lightning and delayed rain: Electrical disturbances in thunderclouds delay the merging of droplets, allowing clouds to store more water before releasing it all at once.
- Carbon loading: Soot from vehicles, fires and crop burning in the Himalayas acts as cloud condensation nuclei, increasing the likelihood of intense rain under orographic pressure.
Hazards of cloudbursts
- Flash floods: sudden deluges overflow rivers and destroy homes, fields and roads.
- Landslides: water saturates steep slopes, triggering landslides and trapping people under debris.
- Mudflows and debris slides: saturated soil mixes with rock and flows at high speed, sweeping away everything in its path.
- Infrastructure collapse: bridges, roads and power lines often fail during these events, hindering rescue.
Challenges in prediction and preparedness
Cloudbursts occur on very small scales and last less than an hour, making forecasting extremely difficult. Existing weather radars have coarse resolution and cannot detect such localised events. There is also no unified national strategy to monitor and respond to cloudbursts.
Suggestions and way forward
- Predictive infrastructure: Expand Doppler radar and automatic weather station networks in the Himalayas; use AI‑based forecasting models for short‑term prediction.
- Institutional coordination: Develop a National Cloudburst Monitoring Programme under the NDMA and ISRO; carry out village‑level micro‑risk assessments using satellite data.
- Land‑use planning: Enforce no‑construction zones in high‑risk slopes; update zonal rainfall intensity maps for all Himalayan towns.
- Community preparedness: Prepare disaster plans in local languages; involve panchayats and self‑help groups in evacuation and relief drills.
- Resilient infrastructure: Use eco‑engineering to stabilise slopes; promote flood‑proof homes and green roofs.
Conclusion: Cloudbursts are not just isolated disasters but symptoms of an accelerating climate crisis. Addressing them requires improved forecasting, resilient infrastructure, responsible land‑use and strong community awareness.