Heavy monsoon rainfall triggered flooding in cities such as Delhi and Surat, disrupting normal life and drawing attention to the recurring challenge of urban floods in India. 

What is Urban Flooding?

• Definition: Urban flooding is the temporary inundation of land or property in urban areas caused by excessive runoff overwhelming the drainage system.
• Differs from rural flooding: as urbanization increases flood peaks by 1.8–8 times and flood volumes by up to 6 times (as per NDMA).
• Impact: displacement, loss of life & property; damage to critical infrastructure (power, water supply); Public health hazards (water-borne diseases, contamination); Environmental degradation (Pollutes water bodies), etc.

 Causes of Urban Flooding 

• Extreme Rainfall & Climate Change: High-intensity rainfall, cloudbursts and changing monsoon patterns, e.g., Mumbai 2005.
• Unplanned Urbanisation: Rapid concretisation and expansion of impervious surfaces reduce infiltration and increase surface runoff.
• Encroachment of Natural Drainage & Water Bodies: Encroachment of lakes, wetlands, floodplains, and storm water drains, e.g., Bengaluru has lost 65 lakes in last two decades.
• Inadequate Storm-Water Drainage: Poorly designed, undersized and poorly maintained drainage systems, often clogged with solid waste.
• Poor Urban Water Management: Sudden release of water from reservoirs/dams and loss of natural catchments, e.g.,2015 Chennai floods due to Chembarambakkam reservoir.