By Vishal Anand
Mumbai Floods 2005 to 2017
the story keep repeating itself?
A 2015 report by the UN Office for Disaster
Risk Reduction (UNISDR) estimated that flooding in India causes an average
economic loss of $7 billion annually, with Mumbai – India’s financial capital,
possessing a total wealth of $82 billion – contributing substantially to the
losses. On August 29th, 2017, Mumbai
received 200 mm of rainfall in 12 hours: the equivalent of 11 days of average
daily monsoon rainfall in half a day. The rains brought the city to a
standstill for about a day, disrupting road, rail and rail travel, and causing
damages to life and property.
This was called the worst case of flooding
since 2005. In 2005, in just 24 hours, Mumbai received 944 mm of rain.
The floods caused the death of over 500 people and halted business
activities for days. The floods caused direct economic damages estimated at almost
two billion USD. Insurance
agencies paid Rs. 3,000 crores that year to vehicle owners and shopkeepers. Research indicates that the intensity of similar
extreme weather events is increasing. Climate change projections clearly
indicate an increase in high-intensity rainfall, and that precipitation events
greater than 100 mm have dramatically increased in number over the past 100
Why is flooding an annual phenomenon in Mumbai?
Historically, Mumbai has been predisposed to
flooding, albeit in a less drastic manner; records corroborating it have been
found in old Portuguese and British journals and gazettes. Being a coastal
city, its flooding is also tightly linked to the tidal movements. In the
previous century, there was a large belt of mangrove swamps along the periphery
of the city that served as a critical buffer against the floods.
reduce storm surge levels by up to half a meter for each kilometer of mangrove
forests that the storm surge passes through. Today, given the astronomical real
estate prices, the ever-growing population and the increasing scarcity of land,
Mumbai has sacrificed its ecology for the sake of development. These mangroves
are now in severe decline, with clearly evident consequences.
Mumbai’s drainage system is also designed to
be able to manage only about 25 mm of rain per hour. In the suburbs, the
drainage capacity is 50 mm per hour through the Brihanmumbai Storm Water
Disposal system projects. However, every year, Mumbai records several days of
heavy rainfall, exceeding 65 mm per hour, which means that even the proposed
enhanced drainage capacity of 50 mm per hour would not be able to accommodate
The issue is further compounded by the changing, urban,
land-use-pattern that prevents water from getting absorbed into the ground. In
areas outside the city, nearly 80% of the rain water is absorbed, and
percolates until it recharges the aquifer. In Mumbai that is replete with concrete
and tar, impervious areas get artificially created. This inhibits water
absorption, that then has no other option but to flow into the already
inadequate drains, eventually causing flooding.
Another aspect that reduces the efficiency of
drains in urban Indian cities is the use of storm water drains as effluent and
sewage disposal systems. Deposits from untreated effluents cause silt to
precipitate to the bottom of water bodies, reducing their volume and capacity. This
is further compounded by the immense volume of garbage produced by the city,
which inevitably finds its way into storm water drains, sewage lines and river
systems such as that of the Mithi river, blocking them, and thereby, lowering
Development and construction of infrastructure on flood-prone
areas and along naturally-occurring watershed channels further hampers the
movement of water and reduces Mumbai’s resilience to withstanding serious
flooding. Thus, the need of the hour is the urgent
revival to the pre-existing ecology of the area along with significant
improvements in waste disposal, and the implementation of environment-conscious
sustainable development practices.
About the author
Vishal Anand is a Research Analyst in the Information Services team of Mitkat Advisory. He graduated from from St. Joseph’s
College, Bangalore,with a Bachelor’s degree in Environmental Science and from Gujarat
Forensic Science University with a post graduate degree in Forensic Science.
Disclaimer: Any views or opinions represented in this blog are of the author and do not represent those of MitKat. Any views or opinions are not intended to malign any religion, ethnic group, club, organization, company, or individual.