(The article was first published on 30 August 2017 after heavy rainfall lashed Mumbai on 29 August. It is being republished from The Quint’s archives in light of the incessant rainfall the city has been receiving since 19 September.)
As Mumbai faced its heaviest rainfall since 2005, many have called out the ineptitude of the Brihanmumbai Municipal Corporation (BMC) that caused a complete collapse of the megalopolis’ infrastructure.
Mumbai’s British-era drainage system, in particular, has been deemed unfit to handle the heavy rains that the city experiences every monsoon.
An Archaic Drainage System
Mumbai’s storm water drainage system (SWDS) was originally designed in 1860 when the British ruled India, to carry a run off resulting from 25 mm rainfall, according to SD Chawathe, consultant and former director (technical), Indian Water Works Association.
As has been seen in recent times as well as in the past, Mumbai experiences more rainfall than its archaic drainage systems can handle. On 29 August alone, Mumbai experienced around 315.8 mm rainfall between 8.30 am and 8.30 pm, according to The Indian Express.
Mumbai’s storm water drainage system is a complex web of drains and rivers, creeks, and drains and ponds, according to a research paper. The same article says that this grid consists of a “hierarchical system of roadside surface drains, underground drains and laterals, major and minor canals, and over 180 outfalls.”
While many of these outlets flow directly into the Arabian Sea, some also drain into the Mithi river, which happens to be an important natural storm water drain in Mumbai.
Urban Flooding Reports Ignored
However, over the years, the Mithi river’s catchment area has been encroached upon by a large number of hutments, processing industries, and scrap yards, which have disrupted the river’s storm water drainage system, according to a paper by two IIT-Bombay researchers.
Also, factories along the catchment area have continued to discharge untreated sewage, wastewater, and industrial effluents, further damaging the river, the research paper by Ravi Ranade and Asad Hasan said.
In 1985, soon after a massive flood, the BMC initiated the Brihanmumbai Storm Water Disposal System (BRIMSTOWAD) project.
After thoroughly studying Mumbai’s SWDS till 1993, the team working on this project submitted a report to the BMC making recommendations. However, these suggestions have for the most part not been implemented, claimed Ranade and Hasan.
In the aftermath of the 2005 Mumbai floods, Kapil Gupta, urban flooding expert from IIT-Bombay, had convened an expert panel under the National Disaster Management Authority. The committee filed India’s first-ever urban flooding report, which emphasised upon the need to treat ‘urban flooding’ as a category unto itself and which needs “to be treated holistically in a multi-disciplinary manner,” reported The Indian Express.
We had recommended that for planning the drainage system in urban areas, watershed (catchment) should be the unit of planning rather than administrative boundaries.Kapil Gupta, urban flooding expert
A report by the School of Planning and Architecture provides a list of major defects in the SWDS, which result in flooding. They are:
- Numerous flat gradients
- Several drains found to be of sparse capacity
- Blockage in larger drains
- Lack of attention to drain repair work
- Links between the storm water drains and sewerage networks
After the 2005 floods, Mumbai had strengthened its flood prediction and warning systems upon the suggestion of a state fact-finding team under Madhav Chitale, a member of the National Ganga River Basin Authority.
However, Mumbai is yet to up the ante as far as city planning and infrastructure are concerned. With a deadline of 2019, BMC has to implement the recommendations of the Chitale committee, mainly doubling the water receding capacity of the drains.
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