Bhavaharini B. | Urban flooding- A case study of Mumbai.
URBAN FLOODING- A CASE STUDY OF MUMBAI CITY
Bhavaharini B, B.Arch. (II-Year), School of Architecture and planning, Chennai.
ABSTRACT
Bhavaharini B.
The following paper is about one of the rising issues in our over populated cities of today, 'The School of Architecture and Planning,
Anna University,
Urban Flooding'. Urban floods are caused by heavy rainfall which overwhelm the drainage Chennai- 600025,
India.
capacity of the city. India has been currently affected by such urban floods in many of its major Mail: harini15700@gmail.com
cities. The reasons for such instances in our country is due to the uncontrolled increase in
population of the cities and the unregulated construction of buildings in the cities' wetlands, flood
plains and low-lying areas. New constructions which do not take into consideration of the existing
natural drain and increased restrictions for water to drain naturally have added into the reasons of
such disasters. This report focuses on the study of Mumbai and hence provides a view on the
existing situations of our cities.
Key words | Urban flooding, India, Cities, Mumbai
INTRODUCTION
India had an urbanization rate of about 28.53% in the 2001 census
The Urban cities of India have been constructed at alarming rates
report and has increased to 31.16% in the 2011 census report.
and now it is almost impossible to find alternative ways to tackle
Being the financial capital of India, Mumbai accommodates 22.1
the problem of Urban flooding. These flooding events have been
million people and is the largest metropolis by population next to
the cases of massive loss of life and causes heavy economic loss
Delhi which has 28 million population. It is also the world’s
for the country. The ways to reduce this deluge is by looking into
seventh most populous city. The reason for the increase in the
different approaches to drain the run-off water because
population of the Mumbai city is due to the surplus job
conventional methods of discharge is not possible in these
opportunities that the city can offer and being a major port of
unpanned and densely populated cities. Mumbai is one such city in
India. Most of the city’s population are in the slums and
the state of Maharashtra in India. It is one of the cities affected by
encroached waterbodies of the city which prevent the water from
urban flooding in India. The Mumbai floods of 2019 is the recent
its’ natural drain into the sea. This urbanization of the city has led
occurrence of such event in Mumbai City.
to its’ destruction and frequent deluge.
Bhavaharini B. | Urban flooding- A case study of Mumbai.
MUMBAI FLOODS 2005 BUILT UP AREA
On 26th of July, 2005, Mumbai received the The figure.1 explains about the urban growth of Mumbai clearly.
highest 24-hour rainfall recording with 1045 mm in Vihar the extension of Mumbai is due to its' rapid urbanization and
lake and 944mm of rain as recorded in Santacruz (official hence the cities are overpopulated. In India, the population from
observation center), Mumbai Airport which caused the the villages migrate to the nearby cities in search of better
devastating floods. The density of Mumbai city was at that amenities for their families, in search of job opportunities or in
time at 28,000 persons per square kilometer. About 13
search of a better economic life.
million people were affected by this. More than 1,00,000
residential and commercial buildings were damaged and The increasing population require adequate shelter and amenities
about 30,000 vehicles were also damaged. thus increasing the built up of the city. The buildings are built
Both flash flooding and river flooding contributed to the
faster and neglect most of the regulations and end up creating a
damages. The most affected areas were the Mumbai slums concrete jungle with no proper drains. The constructions start
since they were near the waterbodies. The rivers were filled encroaching the existing water bodies and wetlands which
and also the drainage systems failed to take in the huge contribute to the reduction in capacity of the water-bodies. The
amount of water coming in a short duration of time. Mumbai slums are the most affected during the rainy seasons
because of their location in the banks of Mithi river and these are
Increased built up area leading to the reduction of open
spaces, green spaces, mangrove cover and also disturbance flooded cause damages to life and livestock.
of the natural drain by altering the hills into flat lands for
further developments and the old drains which were built in
the British era were the human causes for the disaster. The
poor planning of the fast-expanding Mumbai city was the
reason for the disaster to have affected the normal life of the
people of Mumbai.
MUMBAI FLOODS 2017&2019
On 31 August,2017, Mumbai was yet again affected by
floods. It was recorded that around 468mm of rainfall in a
day which is the highest ever recorded in a day. The deluge
killed 21 people.
On September of 2019, yet another Urban flooding affected
the Mumbai city. Around 32 were reported dead and
recordings were recorded to 214.4 mm in 12 hours.
CAUSES FOR URBAN FLOODING
1) Built up area
2) Storm water drainage FIGURE .1
3) Destruction of natural drain
Bhavaharini B. |Urban flooding- A case study of Mumbai. |
STORM WATER DRAINAGE(Figure.2) DESTRUCTION OF NATURAL DRAIN OF THE CITY
Mumbai’s drainage system is as old as 100 years
old. It was constructed during the British period Thousands of acres of mangroves once lined the border
with a capacity of 25mm/hour of rain duration but it between the Arabian sea and the city of Mumbai in western
has been found that 50mm/hour is required to avoid India. They acted as the natural buffers against soil erosion and
flooding of the city streets. flooding. Mangroves can store up to four times as much
carbon. Studies show that nearly 40% of the city’s mangroves
Contributing to the already old and vulnerable were destroyed between 1991 and 2001. At least 32,000
drainage system, there are blockages all through the mangroves were destroyed for the construction of India’s first
drains of the systems and the wetlands are clogged bullet train which will run between Mumbai and Ahmedabad.
with solid waste and sludge from various industries.
The commercial hub of Mumbai in the center of the city is full
After the floods of 2005, the government had taken of shopping malls and skyscrapers are built on reclaimed low-
an initiative called the ‘Brimstowad Project’ with lying land on the banks of Mithi river which was once a
the estimate of 1,200 crore rupees but now it has mangrove forest that acted as a natural stormwater drain and
crossed over 4000 crores and are yet to complete the ironically this area was the most affected during the flood of
project. By the completion of the project the 2005.
capacity of the drains could be increased. This
negligence of the government has led to the Many parts of the city were built on reclaimed land from the
continued deluge affecting the life of the people of sea and are low lying and easily susceptible to flooding.
the city.
FIGURE.3
FIGURE.2
Hydrology Research|
Bhavaharini B. | Urban flooding- A case study of Mumbai
In the context of any city it can be taken that the drainage
system of the city should be well maintained and the natural
drain systems should be restored.
When there is no way to restore the natural context of the city
due to the rapid growth, innovative ideas could be taken into
account of utilizing the existing structures to act as carriers of
the excess rain water and drain it into the water. The existing
structures could be manipulated and they could act as a terrain
itself. The terrace cover can be utilized to catch the rain water
and discharge into the ground. The closely packed buildings
can be manipulated by connecting terraces to drain in a
FIGURE.4 particular direction into the wetlands. Also the grounds and
stadia can be used as places of ground water discharge points.
Figure.3 is the google earth map of Mumbai city in
1984 and Figure.4 is the google earth image of the Restoring the waterbodies to their full capacity is the most
present Mumbai City. One could easily observe the important criteria for the situation of urban floods to decrease
decreased water bodies and the increase in the in our cities.
infrastructure. The density of the city is observed
and that implies less points where the rain water ‘Sponge city’ a possible solution which is being initiated in
could be discharged into. China. This new paradigm in the urban design for flood
control is to allow cities to act like sponges and absorb the
excess water during the wet periods and release it during the
POSSIBLE SOLUTIONS: dry periods and hence use it for consumption. This concept
was made popular by the Chinese president, Xi Jimping at the
The solution to this rising concern in our developing central urbanization conference in December 2013.
cities is to stop and look at the studies and
researches and realize the mistakes we have made
and to rectify it. In case of Mumbai, the possible SPONGE CITY-CHINA
ways are creating more open spaces which might be
very difficult but could at least create punctures and China has taken the Sponge city initiative in 30 cities in 16 of
patches of open spaces where the soil can take up its districts. This initiative is taken up to tolerate the urban
water. flooding and water deficiencies faced b y the rapid urbanizing
cities of China. This initiative includes the installation of Low
Restoring the dying mangroves and increasing the Impact Development stormwater infrastructure. They have set
cover, correcting the bye-laws of the buildings and goals to capture 80%-85% of annual precipitation in Beijing.
to recover, restore or renew the antique drainage
systems of Mumbai City.
Bhavaharini B. | Urban flooding- A case study of Mumbai
The concept of the Sponge City (SPC) was that the
city could act as a sponge that has resilience to
China has started the initiative of SPC and have gained the
environment changes and natural disasters, The
attention of the world. The initiative is one of the many innovative
storm water could be absorbed, stored, infiltrated
ideas that designers and planners are coming up with to prevent the
and cleaned with the help of natural or man-made
urban flooding. This study shows how urban flooding can be
facilities. In this way the wastage of surface run off
reduced at a large scale. For a small scale, campuses, apartments,
into the sea could be controlled.
offices, public buildings and even residential units could adopt
these techniques and contribute to the reduction of the flooding
The construction of the SPC system includes urban
situations.
natural ecological protection, ecological restoration
and LID systems, Urban natural ecological
Indian cities must take up these examples and initiate them to
protection as its name suggests is that the steps
prevent further loss. Though implementation of such ideas are too
taken to protect the natural forests, wetlands, green
expensive, they could help in the decrease of the expenses which
covers, water sheds and so on. It is also considered
we have to spend to mitigate the damages caused during the
the basic requirement of the SPC construction.
flooding.
Ecological restoration is to restore the destroyed
natural ecology which were destroyed due to the
CONCLUSION
unplanned and chaotic urbanization. The LID
system is the concept to reduce the impervious areas
This study considered the example of Mumbai city in India to
of the cities, increasing the stormwater storage,
show how the growing population in cities and the negligence
infiltration and cleaning.
of people, government, construction industry has led to the
mass destruction of property and life in the cities during heavy
Each city which was proposed to become a sponge
rainfall. Water management systems should be given
city was studied and each city was given proposals
importance and ideas to prevent such disasters in the upcoming
based on it geology, existing structures and features
future is to be considered. The study also shows how nature
of the city to make sure each of the city achieve the
when exploited can lead to destruction.
goals of the SPC project.
Designers, architects, urban planners and others must consider
The cities are being converted into SPC by
the effects that might be caused on the environment because of
converting little space assigned as ‘sponge sites. In
the designs and constructions carried out and provide solutions
these sites, the land area are being filled with
for the future problems without creating the problems. These
permeable pavements, rain gardens, grass swales,
initiatives of controlling urban flooding should be carried out
artificial ponds and wetlands and converting many
by the government which should prevent the destruction of the
concrete streets corners into green covers and
natural ecologies of our cities and people should take up the
wetlands. This has also created a pleasant look to
responsibilities of protecting their cities from the disasters by
the cities and creating environments with the lush
following guidelines and creating a better environment for the
greenery and beautiful wetlands.
future.
Hydrology
Research |
Bhavaharini B. | Urban flooding- A case study of Mumbai
Mumbai rains: City receives 418 mm of rain in 12 hours; IMD
ACKNOWLEDGEMENTS predicts more of the same today, First post, August 31 ,2017
This study was supported by the Department of
Architecture, School of Architecture and Planning, Anna Mumbai rains: Flood in Mithi river reason for massive water-
University.
logging, cancelling of local trains, India Today, September
5,2019
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