Mumbai flood has become an annual event that puts the life of Mumbaikars in perishing mode every year during monsoon. Why does it happen? What should be the way out of this problem?
“More dreams are realised and extinguished in Bombay than any other place in India.” – said Australian author Gregory David Roberts. The city abutting the Arabian sea has walked a long way since it changed its name from Bombay to Mumbai in 1995, shedding the British colonial flavour and adopting its typical ‘Aamchi Mumbai’ fragrance. However, the city that Madhuri Dixit once compared with Manhattan still makes and breaks people’s lives, lures many to nourish a dream.
Not only for the outsiders who go to Mumbai in search of luck but the ‘Aam Mumbaikars’ too are probably in search of luck, seeking respite from their annual monsoon mayhem. Heavy rain during monsoon and a flooded Mumbai with the daily lives of Mumbaikars being disrupted has become a very common sight in the last several years. The latest in this list of plight was the series of events that unfurled in Mumbai when heavy rains accompanied by lightning lashed the metro since late Saturday night.
According to Indian Meteorological Department (IMD), the city received nearly 300 mm rainfall in few hours from Saturday night till Sunday morning, recording the highest rainfall in seven years. The roads were flooded, the city’s lifeline Mumbai local trains were suspended, cars and two-wheelers were swept away, buildings collapsed, power outage, water supply suspended, a total of 22 people killed in various incidents related to the heavy rainfall… This list goes on similarly every year. While the whole country watches these plights, Mumbaikars forget and enters their regular schedule as usual after the disruption behaving as nothing happened. They call it the spirit of Mumbai.
Even after the first shower of 2021’s monsoon in June, Mumbai went underwater. What makes the city face such a harrowing situation every year during the monsoon? There are some key factors that play a crucial role in bringing down the city underwater and maximum of it to a standstill. Clogged and overflowing rivers, no existence of wetlands, receding mangroves are automatically leading to flooding in the financial capital of the country and its suburbs as well.
- Poorly planned construction
- Low lying areas
- Clogged, overflowing rivers and no wetland
- Heavy silting in stormwater drainage
- Deforestation of coastal mangrove belt
Poorly planned construction
Mumbai that was originally composed of seven islands has been converted into a metropolis through extensive construction works and many of them are poorly planned. The incessant poorly planned construction has made the city prone to flooding, compromising its safety. As the city is constantly expanding, both laterally and vertically, large scale construction activities are running at a frenetic pace.
This is converting more and more natural space into built-up areas. The land area of Mumbai swelled by almost 50 sq km in the last three decades since 1991. The natural water absorption capability of the land is reducing significantly. The debris and waste generated by the massive construction works are clogging up the drains, preventing the water from escaping.
Low lying areas
Most of the reclaimed land in Mumbai is essentially low lying and as a result, flood-prone. The average height of some stretches from the sea level is less than one metre. Parts of the city are six-eight metres below sea level. Several buildings on the reclaimed land are just above sea level. This becomes a key reason for flooding the city when torrential downpours are accompanied by high tides.
Clogged, overflowing rivers and no wetland
Once the rivers in and around Mumbai used to act as natural stormwater drains, but illegal construction and encroachment have turned the rivers into mere sewers. Take the example of the Mithi river, which is choked with domestic and industrial waste. This clogged river overflows every monsoon. Other rivers like Dahisar, Poisar and Oshiwara too are in a similar situation.
Overall, Mumbai’s natural river drainage system has now been reduced to less than 50% of its original capacity owing to the silt, waste and plastic. The wetlands along with the rivers too are non-existent due to rampant landfills and construction. These wetlands used to act as buffer zones protecting the localities from floods and rising tide levels. But, now with the wetlands gone, there is no buffer between the waterline and residential establishments. When the rivers overflow, the localities too get flooded.
Heavy silting in stormwater drainage
While Mumbai’s natural drainage system’s flow capacity has been reduced by the incessant construction works, pollution and encroachment, the city’s man-made drainage system doesn’t fare much better as well. Built in 1860 by the British colonial rulers, Mumbai’s underground drainage system is more than 160 years old. It was originally built to support the 19th-century population of the city and drain merely 25 mm of rainfall per hour during low tide.
The increasing amount of silts, plastic, construction waste has reduced the water flow capacity of the underground sewers significantly. Rainfall exceeding the 25 mm per hour limit results in floods in the city. In the case of high tide, the situation gets worse. Additionally, major outlets to flush the water away from the city are all below sea level. This means during high tide or heavy rainfall, these underground drains are incapable of flushing out the water from the city
Under the Brihanmumbai Storm Water Disposal System (BRIMSTOWAD), the water flowing capacity of Mumbai’s underground drainage system is being increased to the capacity of 50 mm rainfall per hour. But, the project that was actually conceptualised in 1993 was taken up only after the devastating 2005 Mumbai flood and it is still going on.
Deforestation of coastal mangrove belt
Urbanisation takes place at the cost of deforestation and it was no different in the case of Mumbai. Massive deforestation of coastal mangrove belts has taken place there. This is considered as another contributing factor behind the frequent flooding of Mumbai, especially during monsoon. The city reportedly lost its 40% coastal mangrove cover between 1990 and 2005. While the government’s State of Forest Report 2017 contradicts the data stating that the mangrove forest there has increased since 2015, the present mangrove cover is not adequate for Mumbai.
What’s way ahead
The city and its authorities must find a sustainable solution to this major problem that recurs every year during the monsoon. Pulling the plug on the incessant poorly planned construction work, barring plastic usage, dredging the rivers in and around Mumbai are some of the key steps that should be taken.
Also, the underground drainage system should be updated considering the fact that water levels in the sea are rising due to global warming and the rainfall volumes too could increase substantially in the coming days due to climate change. Forestation in the coastal areas is another step the authorities should take very seriously.