Lessons Mumbai didn’t learn

July 2005 deluge was followed by much planning, Tuesday shows city still cannot deal with heavy rain. Dozens of de-watering pumps for localised relief also suffered technical glitches, as conceded by the municipal commissioner.

Written by Kavitha Iyer | Updated: August 31, 2017 8:35 am
mumbai rains, mumbai, Mumbai rainfall, Mumbai waterlogging, Mumbai weather, Mumbai floods, mumbai heavy rain,mumbai monsoon, mumbai drains, mumbai river, mumbai news, In Borivili, after the Dahisar river overflowed into the streets. At least 11 cars were washed away into the river; countless others are still upside down. (Amit Chakravarty)

Tuesday’s rainfall was only one-third of the rainfall that caused the deluge of July 26, 2005. Yet flood waters did not recede hours after the rain stopped, just like in 2005. And the reasons remain much the same.

The old lot of Mumbai’s municipal engineers often said that the giant underground drain or sewer in which a murderous Amitabh Bachchan is chased and fatally shot by his police inspector son, also Bachchan, was inspired by real South Mumbai drains, wide enough to accommodate several gun-toting men, framed by masonry walls. That was colonial engineering dating back to 1860-1900, some of it continuing to serve Mumbai’s flood waters, but limited to South Mumbai.

The suburbs, where the bulk of Mumbai’s millions live, are served mostly by roadside drains and the nullah system, open drains in which hundreds of tonnes of garbage are chucked each year by citizens, to be removed in an ever-inadequate pre-monsoon ‘desilting’ exercise. Much of these nullah networks also have long routes, flowing several kilometres through congested localities before discharging into the sea, often through outfalls located below mean sea level. This simply means tidal flow rushes into the city, and if it’s raining heavily when the tide is sufficiently high, then drainage is impossible.

But Tuesday’s highest tide had subsided by evening, and flood waters in many places — railway tracks, areas near the Mithi and Dahisar rivers, near large nullah systems —did not recede even past midnight. Notwithstanding the BMC’s and Railways’ claims, this is evidence of inadequately de-clogged drains. Dozens of de-watering pumps for localised relief also suffered technical glitches, as conceded by the municipal commissioner.

Planned, unplanned

Planners with a long-term view have also said part of the problem is that Mumbai’s flood waters are simply discharged in the Arabian Sea through gravity. There are international examples of balancing reservoirs and deep tunnel systems for underground storage of flood waters to be pumped out later when the tides are low. Best practices also involve adopting and conserving rainwater within a catchment area itself, through local storage and recharging alongside filtration systems (Mumbai’s flood waters are among the dirtiest).

While Mumbai’s drains had an average capacity of 25 mm of rain every hour, the system was augmented to tackle 50 mm of rain per hour — in theory at least. And yet experts, including members of a fact-finding committee set up after the July 2005 deluge, have conceded that at least major roads and traffic junctions should have drainage systems capable to tackle floods with a once-in-100-years probability.

In the aftermath of the 944-mm deluge, the state and civic agencies undertook a series of projects, key among them being the decision to finally implement the Brimstowad (Brihanmumbai Storm Water Drainage) project, whose cost had more grown manifold since being proposed in the 1990s. Resources were spent on measures such as standard operation protocol for disaster management units, better-equipped disaster cells and control rooms, better forecasting systems, etc.

Yet, incredibly for a city by the sea, a range of long-term measures, accepted in principle, were never undertaken or were left incomplete. Recommendations to protect the Sanjay Gandhi National Park within the city limits, construct detention basins for flood water, demarcate flood-prone zones on Development Plan sheets, were never undertaken. An initiative to prepare contour maps for a flood modelling system remains incomplete — civic officials confirm that contour maps for drains were prepared, not for the rest of the city. (This means in heavy rain, municipal engineers know which drains’ contours will allow for retention of water longer, but no scientific information exists, for example, on which direction the Mithi river’s flood waters will rush out). Other recommendations to empower the Maharashtra Pollution Control Board to ensure compliance of environmental regulations by municipalities, a Mumbai Watershed Council to advise all agencies on planning for days like Tuesday, etc were never undertaken.

mumbai rains, mumbai, Mumbai rainfall, Mumbai waterlogging, Mumbai weather, Mumbai floods, mumbai heavy rain,mumbai monsoon, mumbai drains, mumbai river, mumbai news, Commutters stranded at Hindamatha, Parel as heavy rains lash on Mumbai city on tuesday.
(Express photo by Ganesh Shirsekar)

The rivers

River floods are different from floods caused by undue, sudden pressure on local drainage networks. By Tuesday evening, it emerged that the Dahisar and Mithi rivers were in spate. The arterial Western Express Highway and Lal Bahadur Shastri Marg were both inundated partially because of the overflowing rivers. Mumbai and its immediate suburbs are home to at least four separate river systems. The Mithi runs nearly 18 km, the Dahisar about 12 km, Poisar and Oshiwara nearly 7 km each. Each of these is now little more than a mother drain for suburban nullah networks, extensive encroachments reducing their width to barely a couple of metres in some places.

In fact, one of the key recommendations of an extensive report submitted by a fact-finding committee after the 2005 deluge was to restore degraded rivers and river-banks, to probe pollution and encroachment problems for each river, identify specific boundaries for each river, establish buffer zones, etc.

In reality, a grand plan for the rejuvenation of the Mithi, responsible for the worst destruction in the 2005 deluge, has been abandoned midway. A holistic revival of the river systems and early warning systems for those living along their banks have been long ignored alongside other related recommendations on reviving or upgrading hill slopes, lakes and ponds.

Response

Casualties were fewer than in July 2005, and it was apparent Tuesday that the state’s response has come a long way since then.

The depth and reach of social media have made Twitter, Facebook and WhatsApp critical tools for dissemination of advisories and real-time situation updates. Mumbai’s Doppler radar-based weather forecasting system was recommended after the 2005 deluge, and installed. Various agencies, connected via hotline after 2005, coordinated effectively.

But advisories to stay indoors came too late, only after the trains had slowed due to submerged tracks and after the first visuals of cars and people stuck in knee-high waters emerged. Also, the CCTV camera network, installed after the Mumbai terror attack, can now monitor areas of traffic congestion and rising floods. It’s unclear yet how well or how early on Tuesday this infrastructure was used to manage the traffic chaos.

Early warning advisory systems the world over are built on the understanding that lead time available for gauging the intensity of an impending disaster and disseminating information is a very small window. For Mumbai, flood warnings based on the intensity of rain in any 15-minute duration are easy to build. The tougher challenge will be drafting detailed but precise advisories that are accurate, localised, accessible to everybody including the millions not on Twitter and disseminated in a well-practised drill.


ELSEWHERE THIS MONSOON

assam floods, assam, floods, northeast floods, assam flood, assam weather, Sarbananda sonowal, bihar floods, floods in india, assam flood update, assam floods death toll, indian express news Flood affected villagers move in a boat in search of higher lands in Pokoria village, east of Gauhati, north eastern Assam state, India, Monday, Aug. 14, 2017. Heavy monsoon rains have unleashed landslides and floods that killed dozens of people in recent days and displaced millions more across northern India, southern Nepal and Bangladesh. (AP Photo/Anupam Nath)

Assam

1141 mm, 157 dead

Over 55 lakh affected in 3 successive waves, crops lost over nearly 4 lakh hectares, nearly 30,000 houses damages. Prime Minister Narendra Modi announced a Rs 2,000-crore package for various flood-mitigation measures in the Northeast. Among other states, Mizoram has received 2,553 mm, Meghalaya 2,109 mm, Arunachal 1,386 mm (48 deaths), Tripura 1,554 mm (6 deaths), Nagaland 1,091 mm (19 deaths) and Manipur 596 mm (22 deaths)

Bihar

806 mm, 514 dead

Crops over 63.67 hectares damaged, over 1.71 crore people affected, 293 animals dead. The Prime Minister has announced Rs 500 crore for the state.

Gujarat

723 mm, 247 dead

Crops worth Rs 867 crore damaged over 10.98 lakh hectares, 6.44 lakh farmers affected. Rs 500 crore announced by PM Modi.

Uttar Pradesh

493 mm, 103 dead

Nearly 27 lakh affected, crop loss estimated at over Rs 98 crore

kavitha.iyer@expressindia.com

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  1. J
    Jiiwan
    Sep 1, 2017 at 6:35 am
    She must consult some real engineer and find out why the Mumbai was flooded in 2005 as well as this ear. The amount of rain was enormous. One cannot prepare for such heavy rains. Just writing an article is not sufficient.
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    1. H
      Harsh
      Aug 31, 2017 at 6:10 pm
      It is very much corrects that flood warnings are easy to build, but it requires proper management on ground to minimize the damage. Fortunately, nature is not in our command we have to adjust ourselves according to nature. We thought with little more developed brain we can manage the nature, but it is not possible. Basically, Bombay is not a natural city it was developed by the British to fulfill their interest. However, due to its economics importance it has developed haphazardly and we allow it to happen without any planning on ground. Everyone knows that it comes under heavy rainfall range and there is no engineering design in place that can easily manage it. Some are earning billions and some do not get minimum that can give them some human life. This, results in development of unfriendly establishment, which are totally contrast to the natural demand of the city. We can still manage it if we plan and execute properly however, that's need some humanity and not any God.
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      1. M
        Mistik
        Aug 31, 2017 at 1:13 pm
        Lot of people don't understand the politics behind the underdevelopment of Mumbai. Mumbai muni l corporation is the only corporation in the country which requires approval from Chief Minister of the state for every work done in the city. And the chief ministers of successive governments have blocked even much needed improvements to the city, e.g. slum rehabilitation, construction regulations, population cntrol etc, due to politics. There is always a tussle going on between the corporation and the chief minister's office. The chief minister can also change the commissioner of the city against the recommendation of the elected representatives on the wimp which happened a few years ago!
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        1. S
          Simbly
          Aug 31, 2017 at 12:31 pm
          So you are saying that the old drainage system that the Brits designed and left in place in old south Bombay about 120 years ago works! We have not even taken that design forward with the growth of the city to the suburbs excepting a few nullas. Wonderful! Where is that Sashi Tharoor - We need to re-check if this British amnesia was really as bad as their futuristic city planning. Chu ya.
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          1. H
            Harminder Singh
            Aug 31, 2017 at 8:49 am
            It's unfortunate that the citizens of Mumbai have got used to slavery nothing new as their contribution to the freedom struggle is practically nil like their Gujju neighbours today there tomorrow gone thankfully no hurricane otherwise it would have been bye bye very wishy washy people
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