Severe Waterlogging in Delhi

On July 9, 2025, heavy rainfall accompanied by strong winds and lightning caused severe waterlogging and traffic disruptions across several key areas in Delhi. The India Meteorological Department (IMD) issued a Red Alert for further rainfall within the next 24 hours.

Urban flooding

Definition and Nature

• Urban flooding refers to the inundation of land or property in densely populated areas due to excessive rainfall, poor drainage, or overflowing water bodies.
• Unlike rural floods, it is intensified by impervious urban surfaces such as concrete and asphalt that hinder natural percolation of rainwater.
• Consequences include waterlogging, traffic paralysis, infrastructure damage, and health hazards.

Causes of Urban Flooding in India

• Rapid Urbanisation and Impervious Surfaces
  • Drastic increase in built-up areas (e.g., 99.9% in Mumbai over 27 years).
  • This leads to 30x more runoff, burdening outdated urban drainage systems.
• Obsolete Drainage Infrastructure
  • Systems often date back several decades (e.g., Delhi’s 1976 master plan).
  • Choked drains due to poor maintenance and increasing waste volumes reduce capacity.
• Climate Change and Extreme Rainfall Events
  • Increase in intensity and frequency of short-duration, high-intensity rainstorms.
  • Example: Chennai recorded 6 mm rainfall in Nov 2015, highest in a century.
  • Central India: Tripling of extreme rain events since 1950.
• Loss of Urban Water Bodies
  • Lakes, wetlands, and ponds are encroached for real estate.
  • Example: Bengaluru has lost 79% of its lakes, reducing water absorption capacity.
• Construction in Eco-Sensitive Zones
  • Unregulated building activities alter natural drainage flows.
  • g., Unplanned development near Kedarnath contributed to 2013 flood devastation.
• Inadequate Solid Waste Management
  • India generates 1.5 lakh tonnes of MSW/day; only <30% treated.
  • Uncollected waste chokes stormwater drains and causes backflow.
• Coastal Vulnerability
  • Coastal cities like Mumbai, Chennai face dual threats: sea-level rise + subsidence.
  • By 2050, Mumbai could face 25% increase in flash floods and 5m rise in sea level.

Impacts of Urban Flooding

• Economic Losses
  • Mumbai (2005): USD 2 billion loss; Chennai (2015): USD 3 billion loss.
  • World Bank projects USD 1 trillion/year global urban flood damage by 2050.
• Public Health Hazards
  • Exposure to sewage-contaminated water spreads diseases (e.g., Leptospirosis).
  • Post-floods in Patna (2019) saw a spike in malaria and diarrhoea.
• Transport and Productivity Disruption
  • IT sector in Bengaluru (2022): Loss of ?225 crore/day due to commuting halt.
• Disproportionate Impact on Urban Poor
  • Slum dwellers in low-lying areas face highest vulnerability.
  • Example: 41–42% of Mumbai’s population lives in slums located in flood-prone zones.
• Mental Health and Trauma
  • Flood-affected populations show 30–40% prevalence of PTSD.
  • Long-term psychological impacts reduce societal productivity and resilience.
• Damage to Cultural Heritage
  • Flooding in Hampi (2019) severely affected a UNESCO World Heritage Site.
  • Loss of cultural landmarks also affects tourism-based urban economies.

Government Initiatives

• Jal Shakti Abhiyan (JSA): Promotes water conservation and aquifer recharge.
• AmritSarovar Mission: Rejuvenation of water bodies for resilience.
• Atal BhujalYojana: Focuses on sustainable groundwater management.
• AMRUT 2.0: Aims for stormwater management and urban drainage reform.

Recommended Solutions for Flood Resilience

• Sponge Cities
  • Use of permeable pavements, rain gardens, and bioswales.
  • China’s pilot sponge cities retain 70–90% of annual rainfall.
• Smart Stormwater Systems
  • IoT-enabled sensors monitor real-time water flow.
  • Singapore’s SWAN project is a global benchmark.
• Urban Wetland Protection
  • Example: East Kolkata Wetlands treat 750 MLD wastewater naturally.
  • Wetlands absorb 1 million gallons/acre of rainwater.
• Green Buildings as Rain Barriers
  • Vertical forests like Bosco Verticale (Milan) reduce runoff and air pollution.
  • Skyscrapers can absorb up to 70% of rooftop rainwater.
• Flood-Resilient Architecture
  • Examples include FLOAT House (New Orleans) and amphibious housing.
  • Elevated, permeable design protects from surface water accumulation.
• Community-Led Interventions
  • Local rainwater harvesting, community-based planning (e.g., Nagdarwadi, Maharashtra).
  • Public spaces like Rotterdam’s water squares serve dual purpose: recreation + flood buffering.