In the last few days, Mumbai floods have once again dominated headlines. Local trains stopped, roads submerged, and large parts of the city almost came to a standstill. This isn’t new. Mumbai witnessed severe floods in 2005, 2017, 2020, and now again.
For UPSC aspirants, Mumbai floods are not just a current affair — they are a classic case of urban flooding shaped by geography, history, tides, and climate change.
Contents
- 1 1. Mumbai’s Low Elevation: A Core Geographical Constraint
- 2 2. Drainage System vs High Tides
- 3 3. Historical Geography: Mumbai Was Once Seven Islands
- 4 4. Role of Marshes, Mangroves and Reclaimed Land
- 5 5. Spring Tides: The Hidden Trigger
- 6 6. Climate Change and Sea Level Rise
- 7 7. Global Comparison: Mumbai Is Not Alone
- 8 8. The Way Forward (UPSC Answer-Oriented)
- 9 Check out our GS Geography Course – Click Here
- 10 FAQs
1. Mumbai’s Low Elevation: A Core Geographical Constraint
Mumbai is a coastal city located barely above mean sea level.
Key facts:
- Average elevation: 10–15 metres
- Large parts of the city: 0–3 metres above sea level
- Areas like Hindmata, Dadar, Lower Parel, Dharavi, Sion, Kurla lie extremely low
- Even premium areas like Nariman Point and Cuffe Parade are less than 1 metre above sea level
During heavy rain or high tides, Mumbai behaves like a basin, trapping water.
2. Drainage System vs High Tides
Mumbai’s drainage is gravity-based, meaning water flows into the Arabian Sea naturally.
The problem:
- During high tide, sea water level rises
- Drain outlets (outfalls) must be closed to prevent seawater entering the city
- When drains are closed during heavy rainfall, water has nowhere to go
Mumbai relies on pumping stations, but:
- Total pumping capacity is limited
- Extreme rainfall overwhelms the system
This creates compound flooding:
👉 heavy rain + high tide = urban flood
3. Historical Geography: Mumbai Was Once Seven Islands
Mumbai was originally a group of seven low-lying islands:
- Colaba
- Worli
- Mazgaon
- Parel
- Mahim
- Little Colaba
- Bombay Island
During British rule:
- Islands were connected using causeways
- Large-scale land reclamation filled shallow waters, salt flats, and marshes
- Projects like the Hornby Vellard Project (1784) altered natural water flow
Many reclaimed areas remain marshy and unstable, making them flood-prone even today.
4. Role of Marshes, Mangroves and Reclaimed Land
Areas like:
- Mahim Creek
- Dharavi marsh
- Sion–Kurla salt flats
were natural flood buffers.
With:
- Mangrove destruction
- Unplanned construction
- Poor drainage maintenance
Mumbai lost its natural flood protection system, increasing vulnerability.
5. Spring Tides: The Hidden Trigger
A key geographical concept UPSC loves — Spring Tides.
Spring tides occur when:
- Sun, Moon, and Earth align
- Happens during New Moon and Full Moon
- Tidal height can reach 4.5 to 5.8 metres
Mumbai becomes extremely vulnerable when:
- Spring tides coincide with heavy monsoon rainfall
This exact overlap often happens in August, making it the most dangerous flood period.
6. Climate Change and Sea Level Rise
According to IPCC reports:
- By 2050, sea level rise could displace ~3 million people in Mumbai
- By 2100, with ~1 metre sea level rise:
- South Mumbai
- Dharavi
- Navi Mumbai
- Coastal belts
could face permanent submergence
Mumbai is among the world’s most climate-vulnerable coastal megacities.
7. Global Comparison: Mumbai Is Not Alone
Similar problems exist in:
- Jakarta (also sinking due to groundwater depletion)
- Bangkok (Chao Phraya River + tides)
- Ho Chi Minh City (Mekong Delta)
- London (Thames Barrier)
- Rotterdam (sea walls and flood gates)
- Kolkata
Cities that invested early in flood barriers and zoning laws fare better.
8. The Way Forward (UPSC Answer-Oriented)
Key measures:
- Strict Coastal Regulation Zone (CRZ) enforcement
- No construction in low-lying reclaimed areas
- Large-scale mangrove restoration
- Expansion of pumping capacity
- Construction of high sea walls and tidal barriers
- Long-term planned retreat and relocation
Urban flooding in Mumbai is not a governance failure alone — it is a geography-driven crisis intensified by climate change.
Check out our GS Geography Course – Click Here
FAQs
- #MumbaiFloodsUPSC: Why does Mumbai experience floods almost every year despite heavy drainage infrastructure?
- #UrbanFloodingIndiaUPSC: How does urbanisation and land reclamation increase flood risk in Indian cities?
- #SpringTidesGeographyUPSC: What are spring tides and why are they dangerous for coastal cities like Mumbai?
- #SeaLevelRiseIndiaUPSC: How will sea level rise impact Indian coastal cities by 2050 and 2100?
