Several devastating flash floods events have recently been occurred in India. First, on August 5, Dharali village in Uttarkashi was struck by flash floods in three consecutive waves that led to the killing of 60 people. Now, in Jammu, at least 65 people were killed in Chasoti in Kishtwar district due to flash flood triggered by torrential rain.
What is Flash Flood?
- According to IMD, flash floods are sudden and rapid floods that occur typically within hours of intense localized rainfall over a short duration or other intense water accumulation events.
- Flash floods are a significant and growing threat in India, particularly in the Himalayan region and parts of central and western India. While traditionally associated with the heavy monsoon season, recent studies and events suggest that their frequency and intensity are increasing, partly due to climate change and human-induced factors.
What are high risk zones in India?
- Western Himalayas: Uttarakhand, Himachal Pradesh and Jammu & Kashmir
- Northeast India: Arunachal Pradesh & Sikkim
- Western Ghats: Kerala, Karnataka, Maharashtra
- Urban Areas: Mumbai, Chennai, Bengaluru, Hyderabad
Examples:
- Kedarnath (2013): Glacial Lake + Cloudburst
- Chamoli (2021): Glacial burst
- Sikkim (2023): Cloudburst
- Uttarkashi (2025): Continuous Rainfall
How flash floods are different from normal floods?
| Normal Floods | Flash Floods | |
| Speed & Duration | Normal floods are a much slower, more gradual process. They can take days or even weeks to develop and can last for extended periods. | Flash floods are incredibly fast, occurring within a very short period, typically less than six hours after the causative event. They build up and dissipate quickly. |
| Causes | Normal floods are generally caused by prolonged, widespread rainfall over a large area, or by snowmelt over a long period. | The primary cause is intense, heavy rainfall in a short amount of time, such as from a slow-moving thunderstorm or a cloudburst. Other triggers include dam or levee failures, sudden glacier melt (GLOFs), or debris jams. The ground simply cannot absorb the immense volume of water quickly enough. |
| Area of impact | Normal floods typically affect a much larger geographic area, following the course of a river system. The flooding is widespread and can inundate entire floodplains, farmlands, and multiple towns. | Flash floods are often localized and can affect small-scale areas like urban streets, dry creek beds (washes), or mountain canyons. |
| Risk & Warning | Normal floods come with much more lead time, allowing authorities to issue warnings and for residents to prepare or evacuate safely. While property damage can be extensive, the risk to human life is generally lower than with a flash flood. The water in a normal flood rises gradually and is often slow-moving. | Flash floods are considered the most dangerous type of flood because of the little-to-no warning time. This leaves people with very little time to evacuate, leading to a higher number of fatalities. The water in a flash flood is a fast-moving, destructive torrent. It can carry a significant amount of debris. |
What are its causes?
NATURAL CAUSES:
- Cloudbursts: This is the most common and devastating cause, especially in the Himalayan states. A cloudburst is an extreme rainfall event where a large amount of rain (over 100 mm) falls over a small area in a very short time, typically less than an hour. The steep slopes of the Himalayas cause this water to rush downhill with immense force, triggering flash floods and landslides.
- Intense Monsoon Rains: The Indian monsoon, which delivers most of the country’s rainfall between June and September (80% of annual rainfall in just 3 months), is a major trigger. Intense, short-duration rainfall events can overwhelm the capacity of rivers and drainage systems, leading to rapid flooding.
- Geological Fragility: The Himalayas are young, tectonically active mountains with fragile geology. Heavy rain and seismic activity can easily destabilize slopes, leading to landslides and debris flows that can block river channels. When these natural dams fail, they release a sudden surge of water, causing a flash flood downstream.
- Topography: Areas with steep terrain, such as canyons and mountains, are highly susceptible to flash floods. Gravity pulls the water downhill at a high velocity, and it can gather in low-lying areas, turning a small creek into a raging river in minutes.
- Glacial Lake Outburst Floods (GLOFs): A GLOF is a sudden and fast-flowing flood that happens when the dam (usually made of ice or moraines) holding back a glacial lake suddenly fails — causing huge amounts of water to rush downstream.
- Wildfires: Recently burned areas are at high risk. The fire-scorched soil becomes hydrophobic (water-repellent), preventing it from absorbing rain and leading to rapid runoff.
ANTHROPOGENIC CAUSES:
- Deforestation: The cutting down of trees reduces the soil’s ability to absorb water, increasing surface runoff and the risk of flash floods.
- Unplanned Development: Unchecked construction, particularly in hazard-prone areas like riverbeds and floodplains, has increased vulnerability and amplified the damage from flash floods.
- Urbanization: In cities, concrete and asphalt surfaces prevent water from soaking into the ground. This creates a high amount of runoff that can quickly overwhelm storm drains and cause streets to flood.
- Poor Drainage: In urban areas, a lack of proper and maintained drainage systems, combined with a high percentage of impermeable surfaces like concrete, leads to rapid water accumulation and urban flash floods.
- Dam Failure: The sudden and catastrophic failure of a man-made dam or a natural ice or debris dam can release a massive amount of water in a very short time, causing a destructive flash flood downstream.
What are its consequences?
- Loss of Life: Flash floods are among the deadliest natural disasters. The sheer force of the water can easily sweep away people, vehicles, and even entire buildings. The lack of warning and the speed of the water leave little chance for escape, especially for the elderly, children, and those with disabilities.
- Destruction of Property: Flash floods can completely destroy homes, businesses, and critical infrastructure. The force of the water, often carrying boulders and debris, can level buildings and wash away bridges, roads, and railways.
- Agricultural Damage: They can devastate agricultural lands, washing away fertile topsoil, destroying crops, and killing livestock. This can lead to food shortages and severe financial losses for farmers, impacting the entire local and regional economy.
- Erosion and Landslides: The powerful flow of a flash flood can cause severe soil and bank erosion, carving out new channels and destabilizing hillsides, which can lead to more landslides and debris flows.
- Habitat Destruction: The sudden and violent change in water flow can destroy natural habitats, uprooting trees, and killing plant and animal life.
What are the various initiatives taken to address the issue of flash floods?
- Flash Flood Guidance System (FFGS): The IMD has implemented the South Asia Flash Flood Guidance System (SASIAFFGS) in collaboration with other South Asian countries. This system provides location-specific flash flood guidance and alerts with a lead time, helping to warn vulnerable communities.
- Early Warning Systems: Efforts are being made to establish early warning systems at the district level, especially in vulnerable mountainous regions. These systems rely on meteorological data, satellite imagery, and real-time monitoring of water levels.
- Disaster Management: The National Disaster Response Force (NDRF) and State Disaster Response Force (SDRF) teams are trained to respond to flash flood events, and their rapid deployment is crucial for search and rescue operations.
- Policy and Planning: There is a growing focus on the need for climate-resilient infrastructure, updated dam design standards, and stricter regulations on development in hazard-prone areas to mitigate the human impact of these natural disasters.
- Hydrological Monitoring: The Central Water Commission (CWC) monitors water levels in major river basins, issuing flood warnings and maintaining a network of flood forecasting stations.
What can be the way forward?
- Strengthen Early Warning Systems and Real-Time Monitoring: Expand the use of Doppler radars, satellite imagery, and artificial intelligence for accurate, real-time prediction and tracking of flash floods.
- Afforestation and Watershed Management: In the Himalayas and other hilly regions, large-scale afforestation and soil conservation projects help the ground absorb more water, which reduces surface runoff and the risk of landslides.
- Improved Drainage Systems: In urban areas, improving and expanding drainage networks is crucial to handle intense rainfall. This includes clearing natural waterways, preventing encroachment on floodplains, and using permeable paving.
- Community-Based Disaster Management: The National Disaster Management Authority (NDMA) and State Disaster Response Force (SDRF) work with communities to train volunteers in search and rescue operations, first aid, and basic emergency response.
- Mock Drills: Conducting regular mock drills helps communities practice evacuation procedures and ensures that residents and first responders are prepared to act quickly when an event occurs.
Conclusion:
With rapidly increasing intensity & frequency of flash flood events across the country, India needs to immediately adopt mitigation & adaptation measures to prevent further loss of lives & property. Authorities need to identify new potential flash flood hotspots & take measures like building climate-resilient infrastructure to limit the limit of extreme weather events.
| Read More: The Hindu, The Indian Express UPSC GS-3: Disaster Management |
