Why in news?

Flash floods have emerged as a deadly and recurring hazard across India, claiming thousands of lives and damaging infrastructure annually. Tragedies in Himachal Pradesh (July 2025), Kerala’s Wayanad (July 2024), Ladakh (June 2024), and Sikkim (October 2023) underline the severity of the crisis.

These sudden and intense floods, primarily triggered by extreme rainfall, have become more frequent with rising global temperatures — increasing from 132 events in 2020 to 184 in 2022, as per the Union Jal Shakti Ministry.

Despite the mounting threat, there remains a lack of detailed research to pinpoint the most vulnerable regions, hampering the effectiveness of mitigation strategies like early warning systems.

What’s in Today’s Article?

• Study Related to Flash Floods in India
• Key Drivers Behind Flash Floods in India
• Climate Change Intensifies Flash Flood Risk in India
• Region-Specific Adaptation Key to Mitigating Flash Flood Risks

Study Related to Flash Floods in India

• A recent IIT Gandhinagar study, published in Nature Hazards, addresses the lack of granular data on flash flood vulnerability in India.
• The study, ‘Drivers of flash floods in the Indian sub-continental river basins’, identifies the Himalayas, western coast, and Central India as key hotspots, using hydrological and geomorphological data to map sub-basin susceptibility.
• In the Himalayas, steep terrain and elevation drive flood risk, while in the West Coast and Central India, rapid runoff—termed "flashiness"—plays a key role.
• The study finds that nearly 75% of flash floods result from a combination of extreme rainfall and already saturated soil, with only 25% due to precipitation alone.
• Alarmingly, even previously low-risk basins are witnessing rising extreme rainfall, suggesting that climate change may create new flash flood zones in the future.

Key Drivers Behind Flash Floods in India

• The study reveals that only 25% of flash floods in India are caused solely by extreme rainfall.
• Most incidents result from a combination of heavy precipitation and pre-existing soil saturation.
  • When the ground is already wet, it cannot absorb additional rainfall, leading to rapid runoff and increased flood risk.
• Notably, only 23% of extreme rainfall events trigger flash floods within six hours. Instead, prolonged periods of both low- and high-intensity rain are more likely to cause such disasters.
• The study also highlights regional variations.
  • In the western coast and Central India, sub-basins react quickly to rainfall due to their high "flashiness" — the tendency of water levels to rise rapidly.
  • In the Himalayan region, steep terrain and high relief further elevate the risk.
  • Within major river basins like the Ganga, flash flood susceptibility differs — sub-basins in the southern Himalayan stretch are more prone, while central areas show lower risk.
• This points to how terrain and local climatic conditions strongly influence flash flood vulnerability.

Climate Change Intensifies Flash Flood Risk in India

• Rising global temperatures are significantly contributing to the increase in frequency and severity of flash floods.
• As the atmosphere warms, it retains more moisture — about 7% more for every 1°C rise — leading to heavier rainfall events.
  • In India, from 1981 to 2020, the incidence of extreme rainfall during the pre-monsoon season doubled.
  • During the monsoon, post-monsoon, and winter seasons, extreme precipitation increased by 56%, 40%, and 12.5% respectively.
  • Notably, over 75% of flash floods between 1980 and 2018 occurred during the monsoon season.
• The study also shows that flash floods have risen sharply since 1995, especially in the Brahmaputra, Ganga, and Krishna river basins.
• Interestingly, many regions that were not previously flood-prone are now experiencing more "wet hours" and higher streamflow due to warming temperatures.
  • 51% of non-prone sub-basins showing increased rainfall and 66.5% showing higher streamflow.
• Conversely, some existing flood-prone areas are seeing a decline in wet hours, indicating shifting climate patterns and flood vulnerabilities.

Region-Specific Adaptation Key to Mitigating Flash Flood Risks

• The study highlights the need for region-specific adaptation strategies tailored to topography, soil conditions, and not just rainfall intensity.
• Such localized approaches can strengthen early warning systems, improve disaster preparedness, and support long-term resilience planning.
• Researchers emphasize the urgency of identifying emerging flash flood hotspots and investing in climate-resilient infrastructure to reduce the impact of extreme events.
• Additionally, with shifting rainfall patterns and rising temperatures, improved land-use planning and integrated flood management are essential for effective mitigation.