UPSC Mains 2016 GS Paper 3 Q15: model answer
The frequency of urban floods due to high-intensity rainfall is increasing over the years. Discussing the reasons for urban floods, highlight the mechanisms for preparedness to reduce the risk during such events.
What the question wants
Discuss why high-intensity rain increasingly floods cities and the preparedness mechanisms to reduce risk.
How to structure it
Reasons, then preparedness.
- The trend
- Reasons
- Preparedness mechanisms
How to think it through
Mumbai 2005 (944 mm in 24 hours), Chennai 2015, Srinagar 2014, Bengaluru 2022, Delhi 2023. Reasons: extreme rainfall rising (climate), encroachment of lakes and floodplains, concretisation, clogged and old drains, solid waste, poor planning, unplanned construction in low areas, tides in coastal cities, release from reservoirs (Chembarambakkam 2015). Preparedness: NDMA Urban Flood guidelines 2010: Urban Flood Cell, DWR network, real-time rainfall, drainage master plans, watershed-based, encroachment removal, sponge city, early warning (Mumbai iFLOWS 2020, Chennai CFLOWS), stormwater design upgrades, rainwater harvesting, community awareness.
Model answer
On 26 July 2005, Mumbai received about 944 mm of rain in 24 hours. The city stopped. A decade later, in 2015, Chennai drowned after heavy rain and a sudden release from the Chembarambakkam reservoir. Urban floods have become a regular feature of Indian monsoons.
Reasons
- More extreme rainfall as the climate warms: more rain falls in fewer, heavier bursts.
- Lost lakes and wetlands: Bengaluru and Chennai built over tanks and floodplains.
- Concrete everywhere: water cannot soak into the ground.
- Old, narrow drains designed for much lower rainfall.
- Garbage and plastic choking drains.
- Encroachment on rivers and nullahs, like Mumbai's Mithi river.
- Poor reservoir management upstream.
- High tides blocking outflow in coastal cities.
Preparedness mechanisms
- NDMA Urban Flood Guidelines (2010): a separate urban flood cell and watershed-based drainage planning.
- Doppler radars and dense rain gauges for real-time warning.
- Flood warning systems like Mumbai's iFLOWS and Chennai's CFLOWS.
- Drainage master plans with higher design capacity.
- Removing encroachments and restoring lakes and wetlands.
- Sponge city ideas: permeable pavements, rain gardens, rainwater harvesting.
- Pre-monsoon desilting and waste management.
- Building rules that ban basements in flood-prone areas.
- Community alerts and evacuation plans for low-lying areas.
- Mapping flood-prone wards and keeping emergency pumps ready. Cities flood because they forgot where water
used to go; preparedness begins by giving it room again.
Draw: A city cross-section: rain → concrete → overflowing drain, vs rain → park and lake → recharge.
Keywords, cases and data to drop in
Mumbai 2005 944 mm, Chennai 2015, Chembarambakkam, Bengaluru 2022, concretisation, encroachment, Mithi river, NDMA urban flood guidelines 2010, DWR, iFLOWS, CFLOWS, sponge city.
Where most answers lose marks
- Blaming only heavy rainfall.
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Question text as printed in the official UPSC Civil Services (Main) question paper. The model answer is original Battle IAS work; use it to learn structure, not to memorise.
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