Rising flash flood risks threaten fragile Himalayan regions

Source: The post Rising flash flood risks threaten fragile Himalayan regions has been created, based on the article “Rain, landslides, flash floods: an uncertain mix” published in “Indian Express” on 9th August 2025

UPSC Syllabus Topic: GS Paper 1- Important Geophysical phenomena such as earthquakes, Tsunami, Volcanic activity, cyclones, etc.

Context: The August 5 flash flood in Dharali village, Uttarkashi, Uttarakhand, killed at least four people and left many missing. The disaster, with widespread destruction and hundreds homeless, has renewed concern about extreme weather threatsin India’s hill states and the growing unpredictability of such events. Rising flood risk in Himalayan regions

Impact and Immediate Circumstances

1. Human and Material Loss: The flood swept away homes, damaged infrastructure, and stranded people. Four deaths have been confirmed, and several remain missing. Hundreds are left without shelter.
2. Wider Regional Pattern: In the last month, Himachal Pradesh saw similar disasters, with dozens killed and thousands affected, showing a rising trend of extreme weather in hill states.

Possible Triggers of the Dharali Flood

1. Rainfall Data: On August 5, Uttarkashi received 32 mm of rain — double the normal for that day but not extreme. In the preceding days, rainfall there was less than in other districts like Haridwar and Udham Singh Nagar.
2. Glacial Lake Breach Hypothesis: A senior glaciologist suggested a possible breach in an upstream glacial lake. Ice-breaks can trigger floods, as seen elsewhere, but this remains unconfirmed.
3. No Cloudburst Evidence: The India Meteorological Department defines a cloudburst as 100 mm rain in about an hour over a 10 km x 10 km area. There was no record or indication of such an event in Uttarkashi.

Understanding Flash Flood Causes

1. Multiple Contributing Factors: Flash floods usually result from heavy rain, landslides or mudslides, and steep slopes causing run-offs into rivers. Not all intense rains or landslides cause floods, and debris may not always reach a river.
2. Role of Glacial Breaks: In Chamoli (2021), 3–4 million cubic metres of water were suddenly released after a glacier collapse. A similar event in Uttarkashi is under investigation.
3. Fragile Geological Conditions: The young Himalayan mountains, with unconsolidated rocks and weak formations, are highly prone to landslides and floods. Saturated soils and erosion can make even low-intensity rain dangerous.

Special Vulnerabilities of the Himalayas

1. Geological Youth: Compared to the older Aravalis, the Himalayas are less stable and more disaster-prone.
2. Seismic Risks: Frequent earthquakes increase instability, making rainfall impacts worse.
3. Human-Induced Stress: Large-scale construction, riverbank activity, and heavy traffic worsen ecological fragility.

Challenges in Prediction and Mitigation

1. Limits of Forecasting: Heavy rain and landslides can be predicted, but it is difficult to forecast if they will cause a flash flood. Dharali showed even moderate rainfall can cause devastation.
2. Need for Preventive Action: Measures include avoiding construction near rivers, relocating villages, and safe disposal of boulders and debris to prevent river blockages.
3. Importance of Preparedness: Unpredictability demands robust planning, early warning improvements, and strict land-use controls to lower risks.

Question for practice:

Discuss the factors contributing to flash flood risks in the Himalayas.