UPSC Mains 2020 GS Paper 1 Q15: model answer

On 13–14 October 2020, Hyderabad received about 190 mm of rain in a day; over 30 people died and colonies built on lake beds stayed under water for a week. Pune had flooded a year earlier when the Ambil Odha stream overflowed.

Natural causes

• Extreme rainfall events are rising: a warmer atmosphere holds more moisture, so short, intense bursts are more common.
• Topography: cities in bowls (Hyderabad's Deccan rocks), on coasts (Mumbai, Chennai) or by rivers (Patna, Guwahati).
• High tides blocking outflow in coastal cities.

Human causes

• Lakes lost to building: Hyderabad's 'city of lakes' lost many of its tanks; the old cascade that moved water from one tank to the next is broken.
• Nalas narrowed or built over: Pune's streams and Mumbai's Mithi river.
• Impervious cover: concrete and asphalt raise run-off sharply.
• Old drains sized for 20–40 mm an hour and choked by solid waste.
• Sprawl into floodplains and low-lying areas through unauthorised layouts.

Governance gaps

• Many agencies, no single owner of drainage.
• Master plans ignore watersheds; smart city projects focused on IT rather than drains.
• Weak early warning and poor dam release coordination.

Lasting remedies

• Map and protect lakes, nalas and floodplains as no-build zones; restore tank cascades.
• Redesign drainage for higher rainfall intensity using watershed-based plans.
• Sponge city measures: rain gardens, permeable surfaces, rooftop harvesting.
• Early warning: Doppler radars, real-time flood models (Mumbai's IFLOWS).
• Urban flood cells under one authority; implement NDMA's urban flood guidelines.
• Housing for the poor away from flood zones.
• Use the 15th Finance Commission's urban flood mitigation funds.

Conclusion

Cities flood where they have forgotten their water. Lasting safety comes from restoring the city's natural drainage, not from bigger pumps alone.