In heavy rain, Mumbai’s new drainage system failed

As Uddhav called it an ‘unprecedented rainfall’, civic chief admits to delay in receding of waters; probe will ascertain if Metro work blocked the drains

Written by Sandeep Ashar | Mumbai | Published:August 31, 2017 1:17 am
Mumbai rains, Mumbai floods, Mumbai rainfall, Uddhav Thackeray, Uddhav Thackeray on mumbai rain, Uddhav Thackeray on mumbai failed drainage system  Shiv Sena chief Uddhav Thackeray with Municipal Commissioner Ajoy Mehta and Subhash Desai at Mayor Bungalow in Dadar on Wednesday. (Express Photo by Dilip Kagda)

When Shiv Sena chief Uddhav Thackeray briefed the media on Wednesday about the heavy rain that had paralysed the financial capital on Tuesday, he claimed that the city had “experienced unprecedented rainfall and you can’t fight against nature beyond a point.” Parts of Mumbai had received 315 mm of rain in 12 hours. Six people were reported dead, several parts of the commercial capital were plunged into darkness, and thousands of commuters were stranded as public transport — suburban railway and the BEST services — failed to run most of Tuesday. Likening Tuesday’s rains to the July 26, 2005, deluge when Mumbai had received three times as much rain, Thackeray, whose party controls the Mumbai municipality, went on to give a clean chit to drain-cleaning works undertaken before the monsoon.

Mumbai Municipal Commissioner Ajoy Mehta also rejected suggestions that poor drain cleaning and training works were responsible for the flooding. While Thackeray was defiant, Mehta admitted that in some places, the rainwater took more time than anticipated to recede.

Meanwhile, data obtained from the civic body contradicted some claims. It showed that several areas in Central Mumbai and suburban Khar and Bandra were flooded even before the hourly intensity of rain increased to 50 mm, which is also the maximum capacity of the city’s upgraded stormwater drainage system. While the gravity-based drainage network was originally designed for a rainfall of 25 mm per hour, the state government and the civic body spent close to Rs 2,200 crore since 2006, for doubling this capacity. Amid rapid construction activity in the commercial capital, the run-off coefficient — percentage of rainfall that can be drained out from a surface — has also increased from 0.5 to 1. Senior sources admitted that the upgradation exercise was implemented following the July 26, 2005, deluge to “better city’s response to extreme rain events.”

But after eleven years and a spend of Rs 2,200 crore, the upgradation project is nowhere near complete. In 2006, the entire project was expected to cost Rs 1,200 crore. The cost has now risen to over Rs 3,500 crore, said sources.

The civic body has already missed two deadlines — 2011 and 2015 — for the completion of the project. While the work for widening the Mithi river that had overflown in 2005 is nearly complete, Mehta admitted that the work for widening and deepening of drains, and that of construction of new drains as part of the upgradation was incomplete. “We have so far completed 84 per cent of this work,” Mehta said. In 2013, the Comptroller and Auditor General (CAG) of India had come down heavily on the state government and the civic body over the “inordinate” delay and irregularities in the execution of the project.

Another worrying indicator is the data that the accumulated rainwater in several parts took more time than expected to drain out, again pointing to the “diversion, narrowing, or clogging of drains.” Data shows that rains had eased across Mumbai by 5 pm.

While the civic administration has contended that torrential rain accompanied by strong winds and a high tide of 3.23 metres slowed the rainwater discharge process between 3 pm and 5 pm, several water-logged areas remained inundated till midnight. In fact, in low-lying belts such as Elphinstone, Hindmata junction, and Sion, the civic disaster cell was receiving complaints of waterlogging till early Wednesday morning.

According to data obtained from the India Meteorological Department, the high tide peaked at 4.48 pm. “We had anticipated that the rainwater will recede by 6.30 pm in most parts. But this took much more time.” On the other hand, Mehta, when contacted, argued that the rainwater had receded in most parts by 8.30-9 pm. Civic chief, however, admitted that there was an unexplained delay in the ebbing of rainwater in the three low-lying belts. The civic body had commissioned a dedicated outfall to pump out water accumulated in the flood-prone Hindmata and Elphinstone Road. While the pumping station was operational, the rainwater still did not recede faster. “This is definitely a concern. We’ll look into it,” Mehta said. Besides the clogging of drains and culverts due to garbage and sewage, senior sources said that the angle that the ongoing Metro construction blocking or diverting some drains or culverts in the Bandra Kurla Complex and Elphinstone is being probed.

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