Recently, heavy pre-monsoon thundershowers in Bengaluru led to severe Floods. Unlike riverine floods, urban floods are highly localised, rapid-onset, and short-duration, but cause disproportionately high economic and infrastructural damage.
Causes of urban flooding
Natural causes
Natural meteorological phenomena like cyclones, cloud bursts. Eg- Cyclone Tauktae in Mumbai.
Climate Change – Increase in short-duration, high-intensity rainfall events. Eg- In 2005 Mumbai witnessed 37 inches of rainfall in only 24 hours.
Sea level rise: by 2050, Mumbai will witness a 25% increase in the intensity of flash floods accompanied by a half-meter rise in the sea level (McKinsey India report)
Topography: Many Indian cities are located in floodplains or low-lying coastal zones. Eg- Mumbai on the Konkan coast, Kolkata in the Ganga-Brahmaputra delta.
Anthropogenic causes
Inadequate Stormwater Drainage Infrastructure – Old, undersized, and poorly maintained drainage networks. Eg- Mumbai’s British-era drainage
Poor urban planning and encroachment on wetlands
Bengaluru has lost 80% of its lakes
Chennai has lost 85% of its wetlands. (WWF)
Concretisation – Expansion of concrete roads, pavements, and buildings reducing infiltration.
Unregulated dumping of solid waste blocks drains, and stormwater systems
Deforestation reduces the land’s ability to absorb water, causing rapid runoff into urban areas.
Weak Enforcement – Lack of floodplain zoning and non-compliance with building regulations.
Sudden release of water from dams and lakes – Eg- Pune Floods due to Opening of Khadakwasla dam.
Illegal river sand mining reduces the water retention capacity of the waterbody, increasing the speed and scale of stormwater flow. Eg- Cauvery River bed, Tamil Nadu.
Two major urban floods in the last two decades in India
Mumbai Floods – 2005
Trigger – Extremely heavy rainfall (~944 mm in 24 hours)
Key Features
Complete failure of stormwater drainage system.
Severe flooding along the Mithi River floodplain due to encroachment.
Massive disruption of transport, power supply, and economic activity.
Exposed vulnerability of coastal megacities to extreme rainfall.
Chennai Floods – 2015
Trigger – Intense northeast monsoon rainfall
Key Features
Encroachment of wetlands like Pallikaranai marsh.
Poor coordination in reservoir water release aggravated flooding.
Prolonged waterlogging in residential and industrial zones.
Policies and Frameworks in India to Tackle Urban Flooding
NDMA Guidelines on Urban Flooding (2010) – Recommend city-specific urban flood management plans.
National Disaster Management Plan (NDMP), 2016 – Integrates urban flood risk reduction within disaster preparedness and mitigation.
Atal Mission for Rejuvenation and Urban Transformation (AMRUT) – Investment in stormwater drainage, sewerage, and water infrastructure.
Smart Cities Mission – Use of GIS mapping, real-time sensors, and flood monitoring systems.
Early Warning Systems – IMD and CWC providing impact-based rainfall forecasts.
Protection of wetlands under Wetlands (Conservation and Management) Rules.
Model Building Bye Laws by MoHUA – all buildings having a plot size of 100 sq.m. or, more shall mandatorily include the complete proposal of rainwater harvesting.
MoHUA has issued Standard Operating Procedures (SoPs) on Urban Flooding in 2017 and published manual on Storm Water Drainage Systems in 2019
As per NITI aayog, over 40% of India’s population will reside in urban areas by 2030. Thus, flood resilient urban future is essential for Viksit Bharat @2047
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