Drought-hit Maharashtra now facing floods fury as impacts of climate change get more pronounced
Extremely heavy rainfall paralyses Mumbai city, while a dam breach in Ratnagiri kills 23 people. The Central Water Commission has issued flood alert in parts of the state that was reeling under an acute drought till a week ago.
Nidhi Jamwal 4 July 2019 6:48 AM GMT
Last October, the chief minister of Maharashtra, Devendra Fadnavis, declared almost half the state as drought-hit. Of the total 358 tehsils in the state, 151 had drought conditions by the end of the last southwest monsoon season (June to September). Some tehsils were already facing drought since the beginning of the last year.
In the last eight months, drought only worsened as some rivers went bone dry and water resources dried up causing mass migration in rural parts of the state. By June 26, Maharashtra had only 5.96% water in all its dams.
A late arrival of this year's monsoon made the matters worse.
As against a 'normal' arrival date of June 10, the monsoon arrived in Mumbai only on June 25, the most delayed in the last 45 years. And, the monsoon arrival caused havoc in the financial capital, as heavy rainfall lead to inundation of several low-lying areas in the city, forcing the state government to declare a public holiday on July 2.
Heavy rains unleashed chaos in some other parts of the state, too. Because of incessant rains, Tiware dam in Chiplun taluka of Ratnagiri, with a capacity of 20 lakh cubic metres, breached on July 2 night leading to death of 23 people and flood-like situation in downstream villages.
In Pune, heavy rains lead to two incidents of wall collapse in which a total of 21 people have been killed. Another wall collapse due to heavy rains in Malad area of Mumbai killed 26 people.
Meanwhile, The Central Water Commission (CWC) has issued a flood alert for several districts in the state for the next five days, indicating possibility of flash floods in some rivers. So far, state-wide flood-related death toll is 35.
Monsoon mayhem in Mumbai
Only a month into the monsoon season, the rainfall has already created new records in Mumbai. In his statement to the Assembly on July 2, Fadnavis noted that the state capital had received second highest rainfall in the last 45 years with the entire June month's average rainfall (about 550 millimetre) received in just three days period in Mumbai.
For instance, in 24 hours ending 8.30 am on July 27, the India Meteorological Department's (IMD) observatory at Santacruz in Mumbai suburbs recorded 234.8 millimetre (mm) rainfall within a single day.
Heavy rainfall continued in July month with Santacruz recording 375.2 mm rainfall within 24 hours ending at 8.30 am on July 2, making it the second rainiest day in July month in Mumbai since July 1974.
Moreover, within the initial three days of July (July 1 to July 3), the city (Santacruz observatory) received 501.3 mm rainfall. The entire July month average rainfall for the metropolis is about 840.7 mm. Thus, Mumbai has already received 60 per cent of its July average rainfall within three days period.
Rainfall data with the IMD's Regional Meteorological Centre, Mumbai shows that the cumulative rainfall over Santacruz from June 1 this year till July 3 is above normal. In the four months of southwest monsoon season (June to September), Santacruz observatory receives an average of over 2,200 mm rainfall. Till July 3 this year, Mumbai (Santacruz) has already received 1,000 mm rainfall, or almost half its annual rainfall (see graph: Cumulative rainfall over Santacruz, Mumbai).
Predictably, such heavy downpour unleashed chaos in the financial capital, which had faced unprecedented floods in July 2005 when the city received 944 mm rainfall within 24 hours.
Trains were cancelled, streets were water-logged, people stranded and houses flooded leading to huge losses.
The Municipal Corporation of Greater Mumbai (MCGM), which has an annual budget of Rs 30,692 crore for 2019-2020, received flak from the Mumbaikars for alleged shoddy pre-monsoon works and poor flood-preparedness.
However, the municipal commissioner, Praveen Pardeshi, chose to blame climate change and over concretisation of the city for the monsoon mayhem. Speaking to media, Pardeshi said that whereas the cumulative annual rainfall over Mumbai had not changed, the incidences of heavy rainfall in shorter duration had increased and the city's stormwater drainage system wasn't upgraded to handle such heavy run-off. He also noted that as against other cities where run-off was only 60 per cent of the total rainfall, in Mumbai the run-off was almost 100 per cent, meaning whatever rain falls on the city gets converted to run-off without any amount of rainwater seeping into the ground.
Climate change and extreme rainfall events
But, Pardeshi and Fadnavis should know that impacts of climate change on extreme weather events, such as the heavy downpour and deluge in Mumbai, have been flagged off to the state government in the past. It was upon the authorities to act on those issues.
A decade ago, in May 2009, the Regional Meteorological Centre, Mumbai submitted a report titled 'Environmental degradation, disasters and climate change' to the state chief minister informing that Mumbaikars needed to brace themselves for more natural disasters as extreme weather events, such as the July 2005 floods, may not be a one-off event. The authors of the report argued that human activity induced environmental degradation was responsible for global warming, which could lead to increased incidence of extreme weather events in Mumbai.
This is not all. The state's climate action plan, Assessing Climate Change Vulnerability and Adaptation Strategies for Maharashtra: Maharashtra State Action Plan on Climate Change (MSAAPC), prepared in seven years by The Energy and Resources Institute, too, noted the risks and challenges the state faces due to climate change.
The action plan, approved by the state government in October 2017, delves in detail on the risks of climate change, heavy rainfall events and flooding in Mumbai. It reads that if an extreme rainfall event, like that of July 26, 2005 takes place again, then several areas in the city would be "flooded even at an augmented drainage capacity of 50 mm/hour".
At several locations in the city, the present stormwater drainage capacity is 25 mm per hour, which has been proposed to be upgraded to 50 mm per hour. But, the climate action plan notes that even with an upgraded capacity, the chances of flooding in the city will remain due to instances of extremely heavy downpour in a changing climate.
The risks Mumbai faces are acknowledged internationally. In its 'Climate Change and Environmental Risk Atlas 2013', the UK-based Maplecroft has ranked Mumbai eighth in the global list of total 50 cities (chosen for their current and future importance to global business) that face a range of risks due to climate change. The 2013 atlas clubs Mumbai under "high risk" category in the climate change vulnerability index.
"Due to global warming and climate change, we should expect more and more extreme weather events like intense precipitation and heat waves in the country," M Rajeevan, secretary, Union ministry of earth sciences told Gaon Connection.
Supporting Rajeevan's statement, Sridhar Balasubramanian, associate professor with department of mechanical engineering, Indian Institute of Technology (IIT) Bombay said that climate change has a role to play in such extreme weather events.
"With global warming, the ocean is heating up, fueling more extreme events. The local wind patterns are also affected and therefore, the local weather dynamics has a lot of variability associated," said Balasubramanian. According to him, the authorities should identify highly potential areas of flooding during such extreme events and ensure drainage and the ground recharge mechanisms are intact in those places. "Mumbai's concrete jungle has made it difficult for the rain water to seep into the ground. Therefore, it just keeps flowing rather than seeping in," he added.
According to Rajeevan, because of climate change, urban cities are becoming more and more vulnerable. "City administration should start thinking on these issues and make a comprehensive decision support system for mitigation of these extreme weather events. They should be better prepared with a good strategy to cope up. Also, they should take public support in implementing them," he said.
The IMD is preparing a Mumbai Flood Warning System, which will be ready by the next monsoon season. By that time, the rainfall monitoring network will also be strengthened with four additional doppler weather radars in the city, which will help general public and the government authorities to forewarn and limit damages and save lives, informed Rajeevan.
Several reports and delayed actions
While the city administration and the state government have seemingly sprung into action after the recent heavy rainfall in Mumbai and the resultant water logging, a number of projects and recommendations to control flooding, proposed decades ago, remain in limbo.
Mumbai has an extensive system of stormwater drainage, as documented in the December 2010 report, 'Mumbai: Towards Unique World Class City, of a non-profit Mumbai Vikas Samiti, whose members are the former MCGM officials. This report notes the city has 565 km long closed dhapa drains and 151 kms of arch drains for draining the run-off. Apart from these, Mumbai also has 200 kms long major nullahs (more than 1.5 metre wide) and 129 kms long minor nullahs (less than 1.5 metre wide). Another 1,987 kms of road side open drains empty the runoff into the minor or major nullahs.
All the nullahs and drains empty into the creeks and the Arabian Sea at points known as stormwater outfalls. The island city, the eastern suburbs and the western suburbs together have 186 such outfalls to drain excess rainwater from the metropolis. But, 45 of these outfalls are below mean sea level. Another 135 outfalls are above mean seal level, but below high tide level. Only six outfalls are above the high tide level. Thus, continuous heavy downpour coinciding with high tide is a sure recipe for flooding in the city.
According to Balasubramanian, if there is a rainfall rate of 140 mm per hour, there is nothing much anyone could do about it. During the recent Mumbai rains, some areas (IIT Bombay) received a whopping 450 mm rainfall in 24 hours. "Internationally, stormwater drains are designed for 50-60 mm/hr rainfall events… we need to at least get our drainage system to the global standards. This will curb the extreme flooding events to some extent," said Balasubramanian.
A number of reports in the past have stressed on the need to upgrade Mumbai's stormwater drainage system. For instance, a 1993 report on Bruhan Mumbai Storm Water Drainage project, commonly known as BRIMSTOWAD, suggested increasing nullah capacity from 25mm per hour rain to 50mm per hour rainfall; and increasing the run-off co-efficient from 0.5 to 1 (meaning whatever rainwater falls converts into run-off). But, almost no progress was made on this for 12 years and the city faced unprecedented floods in July 2005 leading to financial losses worth US$ 100 million.
Thereafter, a Fact Finding Committee, also known as Chitale committee, was set up by the state government to look into the reasons for the 2005 floods and suggest remedial measures. The committee submitted an interim report in December 2005 and a final report in 2006, which suggested, among several other things, setting up of eight pumping stations to drain out excess water from the city.
Thirteen years later, only six pumping stations have been set up. Two pumping stations are yet to see the light of the day.
The capacity of some nullahs has been upgraded from 25 mm per hour to 50 mm per hour, but experts point out that keeping in mind the instances of heavy precipitation days, stormwater drainage system should further be upgraded to 75 mm per hour capacity.
Recognise and protect 'green infrastructure'
Apart from the stormwater drainage system that tries keeping the city afloat during rainy days, Mumbai also has an extensive 'green infrastructure', including the forests, rivers, lakes, wetlands, mangroves, creeks, salt pan lands, that offer protection to the city against the vagaries of nature. For instance, rivers such as Mithi, Oshiwara, Dahisar and Poisar are part of the city's natural drainage system. Mangroves along the city's coastline help drain out excess water. Salt pan lands at the outskirts of the city are the sponges that hold excess rainwater during heavy rainfall days.
Writing on the importance of Mumbai's 'green infrastructure', Harini Nagendra, professor of sustainability at Azim Premji University notes in a September 2017 article: "Mudflats, wetlands, floodplains, mangroves and wooded vegetation once slowed down the flow of storm water. The mangrove's complex root systems and the branching architecture of trees acted as a natural barrier to reduce the force of water flow. But now, they are built over. Garbage spread everywhere clogs the waterways. Most channels and waterways that connect water bodies have been built over too, resulting preventing streams from easily reaching the sea – forcing it to spread out into the low lying areas of the city, adding to the severe flooding."
In the name of 'development', the state government has been promoting projects that are a direct attack on the city's 'green infrastructure'. For instance, the Mumbai-Ahmedabad bullet train project is expected to cost at least 54,000 mangroves spread across 13.36 hectares area.
The Navi Mumbai International Airport is coming up on coastal regulation zone (CRZ) by chopping off mangroves, flattening of a hillock, diverting one river and training another river. There are protests against the proposed Metro shed in Aarey 'forest' in Mumbai suburbs, which, allege activists, will lead to cutting down of thousands of trees on 33 hectare area.
While Pardeshi is blaming over-concretisation of Mumbai for flooding, it is the city planning authorities that have been promoting such urban 'development'.
According to Rajeevan, the city administrations should not allow any development, which may hamper the environment. "Water bodies like lakes and marshy land should be retained as during the floods they will act as sinks and reduce the intensity of floods. For example, in the Kerala floods last August, it was very evident that environmental degradation added more miseries," he said.
Rain water harvesting needs to be made mandatory, said Balasubramanian. "We are getting enough rains, but in short bursts. The recent trend has been long break period of rain and very short period of high activity rains. We need to find ways to harvest the rainwater. That and only that is going to save us," he added.
During the recent heavy rainfall activity in Mumbai and the consequent flooding in parts of the city, the MCGM tweeted that the six pumping stations had pumped out more than 14,000 million litres of water into the sea.
The municipal corporation also supplies 3,420 million litres of water daily to the city's residents. Mumbaikars must remember this water comes from over 150 kms away from lakes built in the adjoining Thane district, where local tribal population faces acute water scarcity.
While villages go dry, Mumbai continues to pump its sewage and the run-off into the sea.