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A global study published in Nature Cities has revealed that India has the highest number of slum clusters in flood-prone areas worldwide, underscoring the nexus between rapid urbanisation, poverty, and increasing climate-related risks. This trend highlights both developmental and governance challenges for India as it seeks to balance inclusive growth with climate resilience.

Global Trends in Flood Risk and Slum Settlements

• India at the Forefront: Over 158 million slum dwellers live in flood-prone areas in India, particularly in the Ganga delta. Nearly 40% of slum residents inhabit high-risk urban and peri-urban zones.
• Regional Pattern: India is followed by Indonesia, Bangladesh, and Pakistan in terms of vulnerable populations. Globally, slum dwellers are 32% more likely to reside in floodplains than other communities.
• Global South Impact: About 33% of informal settlements in low- and middle-income countries are already exposed to flooding. Hotspots include Rwanda, Morocco, and coastal Brazil.
• Cities at Risk: High slum density correlates with flood-prone megacities such as Mumbai and Jakarta.

Drivers of Flood Vulnerability in India

• Riverine Floods: Frequent in the Brahmaputra, Ganga, and Krishna basins, driven by monsoon rains, snowmelt, and dam-related issues.
• Urban Expansion: Between 1985–2015, India ranked third globally in urban growth into flood-prone areas. Cities like Mumbai and Bengaluru have expanded into natural floodplains.
• Flash Floods: Incidents rose from 132 (2020) to 184 (2022), with severe events in Himachal Pradesh (2025), Wayanad (2024), Ladakh (2024), and Sikkim (2023).
  • 75% of flash floods stem from a mix of extreme rainfall and saturated soils.
• Climate Change: Between 1981–2020, extreme rainfall events doubled, with monsoon rains intensifying by 56%, raising flood frequency.
• Poor Drainage & Encroachments: Urban floods in Delhi, Mumbai, Hyderabad, and Chennai worsened by clogged drains and plastic waste (e.g., Chennai floods 2015).
• Weak Local Planning: Absence of region-specific flood risk assessments hampers effective urban land-use planning and disaster preparedness.

Slums in India: Extent and Challenges

• Definitions:
  • Pranab Sen Committee (2010) – compact settlements of ≥20 households with poor housing, sanitation, and water facilities.
  • UN-Habitat – lack of durable housing, secure tenure, sufficient living space, safe water, or sanitation.
• Census 2011: 17% of urban India lived in 1.39 crore slum households.
• NSSO 2012: 33,510 slums identified nationwide.
• Hotspot States: Maharashtra, Andhra Pradesh, Uttar Pradesh, and West Bengal.
• Major Cities: Mumbai and Kolkata host some of the densest slum populations.
• Regulation: The Slum Areas (Improvement and Clearance) Act, 1956 governs slum rehabilitation in Union Territories; “Land” and “Colonisation” are State subjects.

Existing Initiatives

• Pradhan Mantri Awas Yojana – Urban (PMAY-U): Pucca houses with amenities; as of Dec 2024, 118.64 lakh houses sanctioned, 29 lakh for slum dwellers.
• AMRUT & Smart Cities Mission: Infrastructure upgrades in water, sanitation, and drainage.
• Swachh Bharat Mission – Urban 2.0: Target of garbage-free cities.
• IFLOWS-Mumbai and CFLOWS-Chennai: Integrated flood warning systems.

Way Forward: Towards Sustainable Urban Flood and Slum Management

• Region-Specific Flood Strategies: Based on topography and soil; integrate into the National Disaster Management Plan (NDMP).
• Restrict Expansion into Floodplains: Enforce zoning laws and incorporate flood-resilient infrastructure under Smart Cities Mission.
• Sustainable Urban Drainage Systems (SUDS): Rain gardens, permeable pavements, and green spaces.
• Upgrading Slums: Use PMAY-U for resilient housing, raised plinths, and better drainage.
• Data-Driven Risk Mapping: Use NRSC, IMD, and satellite imagery to monitor risks and emerging hotspots.
• Sponge City Model: Adopt Shanghai-style rainwater absorption systems; Mumbai has begun implementing this.
• Eco-Restoration of Water Bodies: Revive urban lakes/wetlands (e.g., Jakkur Lake in Bengaluru) for natural flood control.
• Climate Adaptation Mainstreaming: Integrate climate resilience into urban planning and housing policies.

Conclusion

India’s dual challenge of informal urbanisation and intensifying floods poses a direct threat to sustainable urban development. As the 2030 Sustainable Development Goals (SDGs) approach, urgent focus is needed on SDG 11 (Sustainable Cities), SDG 6 (Clean Water and Sanitation), and SDG 1 (No Poverty).
Strengthening governance, upgrading slum infrastructure, and integrating climate resilience into planning are critical to safeguard millions living at the intersection of poverty and environmental risk.