01 · The problem
What is happening
Mumbai receives most of its annual rainfall during the southwest monsoon. When very heavy rain coincides with high tide, outfalls into the sea can be blocked, and water backs up through an ageing drainage network. Much of the city sits on land reclaimed from the sea and from the channels that once separated its islands, and natural drainage paths such as creeks, rivers and mangrove areas have been narrowed or built over. The extreme rainfall of 26 July 2005 caused catastrophic flooding and loss of life, and prompted major reviews of drainage and flood preparedness.
High severity. Serious, widespread effects requiring sustained action. Severity is descriptive editorial metadata summarising documented effects. It is not a measured index or a score.
02 · Causes
Why it is happening
- 01
Extreme monsoon rainfall
Short, intense bursts of rain can exceed the capacity of storm drains designed for lower intensities.
- 02
Tidal backwater effects
High tides reduce or block discharge from drains into the Arabian Sea.
- 03
Encroachment on rivers and creeks
Construction along the Mithi River and other channels reduces their capacity to carry floodwater.
- 04
Solid waste in drains
Plastic and other waste block drains and culverts, worsening local waterlogging.
03 · Impacts
Who and what it affects
- 01
Disruption to transport and work
Suburban rail and road networks can be halted, affecting millions of daily commuters.
- 02
Risk to life and property
Flooding, building collapses and landslides during heavy rain cause deaths and damage, especially in informal settlements.
- 03
Waterborne and vector-borne disease
Floodwater contact and standing water are associated with leptospirosis and other disease risks after heavy rain.
- 04
Economic losses
Business closures and damaged goods impose costs on households and firms.
04 · Solutions
Documented approaches
Storm drain upgrades and pumping stations
Widening drains and building large pumping stations at outfalls to discharge water during high tide.
Expected effectReduces the duration and extent of waterlogging in served areas.
Protecting mangroves and river corridors
Legal protection and restoration of mangroves and clearing encroachments along the Mithi River.
Expected effectRestores natural drainage and storage capacity and buffers coastal flooding.
Climate action planning and early warning
The city's climate action plan and automated weather stations support forecasting and targeted response.
Expected effectImproves preparedness and prioritisation of investment.
05 · Key indicators
What can be measured
- Landmark event
- 26 July 2005 flood2005
Record rainfall caused severe flooding across the metropolitan region and led to a major review of drainage infrastructure.
06 · Sources
Where this comes from
- [1]Municipal Corporation of Greater MumbaiBrihanmumbai Municipal Corporationmcgm.gov.in(opens in a new tab)
- [2]India Meteorological DepartmentGovernment of Indiamausam.imd.gov.in(opens in a new tab)
- [3]Climate Change 2022: Impacts, Adaptation and VulnerabilityIntergovernmental Panel on Climate Change · Feb 2022ipcc.ch(opens in a new tab)
Links open the publishing organisation's site. Some point to the publisher's main page, where the named report or dataset can be found.