About Flash Floods
- They are sudden floods characterized by a rapid rise and recession of water levels, usually developing within six hours of intense rainfall or other triggering events.
- Status in India
- Occurrence: 75% of events occur during the Southwest Monsoon (June–September).
- Increased frequency: From 132 events (2020) to 184 events (2022). (Union Ministry of Jal Shakti)
- Major flash flood hotspots: In the Himalayas, West Coast and Central India.
- Among river basins, the Brahmaputra records the highest number of events, followed by the Ganga and Krishna basins.
Major Drivers of Flash Floods
- Meteorological Drivers: Extreme rainfall, cloudbursts, monsoon depressions, cyclones and thunderstorms, sometimes driven by climate change.
- Hydrological Drivers: Saturated soil, prolonged rainfall, high basin flashiness and impervious urban surfaces reduce infiltration and accelerate runoff.
- Geomorphological Drivers: Steep slopes, high relief, dense drainage networks and basin shape accelerate runoff.
- Cryospheric Drivers: Glacial Lake Outburst Floods (GLOFs), glacier melt and landslide dam failures trigger sudden floods in Himalayan river basins.
- Anthropogenic Drivers: Floodplain encroachment, urbanisation, poor drainage, deforestation, reservoir releases and embankment breaches amplify flood risk.
Way Forward to Reduce Flash Flood Risk
- Strengthen early warning systems (Automatic Weather Stations (AWS), Doppler radars, satellite monitoring and real-time forecasting).
- Prepare scientific hazard maps and identify vulnerable sub-basins.
- Promote nature-based solutions such as wetland, forest and mangrove restoration.
- Enforce floodplain zoning and climate-sensitive land-use planning.
- Develop climate-resilient infrastructure and improve reservoir management.
