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Why a flood-free Mumbai is wishful thinking

Forget being flood-free, Mumbai needs to urgently prepare to face annual floods and bounce back with minimum damage 

June 14, 2021 / 03:50 PM IST
 (Image: News18)

(Image: News18)

This year the monsoon arrived in Mumbai on June 9, two days before schedule, and brought in a spell of heavy to extremely-heavy rain. The romance of the first rain falling on a hot and concretised city retreated rather quickly, as it always does, and was replaced by the nightmare that Mumbai monsoon is now synonymous with: flooding and disruptions.

It took barely three hours of hard rain that day for a number of areas to be water-logged. Vehicles struggled to stay on ground and people afloat, suburban train services were suspended for a few hours when tracks were inundated, several bus routes were cancelled, and airport operations were severely disrupted. The Brihanmumbai Municipal Corporation (BMC)’s claim of having de-silted storm water drains last month making Mumbai ‘rain ready’ fell flat yet another year. The story of the past many years repeated itself.

Will Mumbai ever be flood-free? The BMC officials aver that Mumbai has been facing occasional floods but that’s par for the course in a large, uneven and dense coastal city. Economists and industry leaders, worried about the enormous losses that pile up every monsoon, believe Mumbai can coast along like other international cities do with additional infrastructure.

Climate Change advocates point to the urban heat island effect, denudation of open green spaces, and continued reclamation of the sea to foretell that Mumbai may have more — not fewer — floods in the coming years. Many politicians blame rival parties or politicians for civic mismanagement which they hold responsible for the water-logging.

The reality is more complex than all these together.

Close

Making Mumbai flood-free is neither a simple infrastructural issue nor only a matter of electing the right party to govern. The BMC with its annual budgets of Rs 25,000-30,000 crore in the last few years should not ideally cite a resource crunch to address this vital issue which disrupts urban life every year.

Since the watershed flash flood in July 2005, targeted anti-flood measures have been adopted. These include cleaning the Mithi River, augmenting the capacity of storm water drains, setting up radars and Advance Warning Systems in 60 locations, de-silting the drainage system before the monsoon, and installing water pumps to drain out rain water. More can be done, but these do not seem to have helped.

Perhaps, the question to ask is: Can Mumbai ever be flood-free? The answer flows into many realms.

First, Mumbai’s natural and unique topography renders the city somewhat like a saucer with dips in its centre where rain water tends to collect. Also, popular culture paints Mumbai as an island city, but the complex reality is that it is more an estuary with rivers running into spaces between little natural islands which were made contiguous by reclaiming the sea in between them. Together, this means several low-lying areas across the city where rainwater will naturally collect, sometimes for hours.

Second, the natural disadvantages are compounded by human factors: construction permits were issued in the last four decades without foregrounding the topographical factors, rampant concretisation of pavements and private areas reduced the soaking capacity of top soil, Mumbai’s four major rivers — Mithi, Oshiwara, Poisar and Dahisar — have been used as sewage drains severely compromising their capacity to carry rain water to the sea.

New infrastructure such as the Worli-Bandra sea link and under-construction coastal road disrupted the inter-tidal areas and mangroves which were like Mumbai’s kitchen sinks, urban footprint increased by three-four times in the last four decades reducing open areas where rainwater stood and gradually seeped in, continued reclamation and shifting coastline brought the sea closer to the city when its level has risen due to Climate Change. Therefore, tides hit the city harder than earlier. When severe rainfall coincides with high tides, as it does twice-thrice every monsoon, drains are thoroughly overwhelmed by tidal water and rain water, leading to floods.

Third, floods and water-logging have increased in the last 15 years or so. Academic studies show that Mumbai has had more extremely heavy rain days during every monsoon in this time than any time earlier, that these are a feature of the annual monsoon and not an outlier phenomenon, that the average heavy to very-heavy rainfall tends to be 120 to 280 millimetres in 12 hours, which is the equivalent of six to 12 days of rain in half a day, and that the inconsistencies in rainfall across the city — south Mumbai records in two digits while suburbs get over 200 mm the same day — challenges most urban planning and mitigation measures.

In August 2017, when Mumbai came to a standstill, Andheri, where the airport is located, recorded a staggering 315 mm rain in a day; the overflowing Mithi and storm water drains could not carry it all to the sea. Last August, the city recorded 331mm rain in a day. Urban planners say it is hard to design or construct drainage systems to handle such a load; there is no option but to build Climate Change mitigation measures into the city’s flood management.

Forget being flood-free, Mumbai needs to urgently prepare to face annual floods and bounce back with minimum damage — that’s being flood-resilient.
Smruti Koppikar is a senior Mumbai-based journalist and urban chronicler. Views are personal.
first published: Jun 14, 2021 03:50 pm

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