Here’s Why Kolkata Will Remain Vulnerable To Waterlogging

Vast swathes of Kolkata remained under water for a few hours on Saturday and Sunday, and some pockets in the city remained marooned on Monday as well. This, despite the 250-odd pumps working round-the-clock to drain out storm water.

The city received a record 191 mm of rain, more than half its average August quota of 335 mm, in a little over 24 hours since Friday (16 August) afternoon. But the intense downpour alone cannot be blamed for the the city going under water.

Generations of Kolkata’s short-sighted and inefficient planners, its negligent citizenry, avaricious builders and the city’s topography itself is responsible for the mess the city finds itself in after every heavy downpour.

These are the reasons behind Kolkata getting submerged, and remaining so for hours, during intense rain spells:

Topography

The natural gradient of the city is from west to east, with the Hooghly (a tributary of the Ganga) forming its western boundary (see map). The central part of the city is like a soup bowl with storm water flowing into it from surrounding areas.

Earlier, the eastern part comprised vast marshlands and wetlands where storm waters would flow into and which were natural soak-pits for the city’s sewage.

Soil Conditions

The city’s soil is semi-pervious alluvial clay, which does not soak in water very fast. The densely-populated western and central parts of the city have new alluvial clay which is more impervious, and so rainwater does not readily permeate the soil.

Choked Canals

Canals which used to drain off storm water to the marshlands and wetlands to the east of the city have got completely choked and virtually nothing has been done by the city’s civic authorities to dredge them. Hence, they can no longer carry the large volumes of storm water that used to flood the city even three decades ago.

Studies have shown that their drainage capacity has decreased by more than 50 per cent over the last four decades.

Plastic Menace

Kolkata’s irresponsible citizenry is also to blame for the mess. Despite awareness programmes and appeals, Kolkatans continue to use plastic bags and throw them into drains.

Segregation of waste is unheard of and garbage-collection itself is not very efficient. This results in the city’s drains and sewers getting clogged. The efficiency of pumps meant for draining out water thus gets severely constricted.

Rampant Urbanisation

Kolkata becoming a concrete jungle is a major reason for it getting water-logged. Residential high-rises impose a severe strain on the city’s 135-year-old sewers that were built by the British for just a small fraction of the city’s current population of 4.5 million (2011 census).

Also, concreting has obliterated the limited prospects of rain water getting absorbed into the soil. With more high-rises coming up, this problem is only going to get worse.

Filling Up Water Bodies

Avaricious builders, in league with corrupt civic officials, have filled up almost all water bodies that ringed the city. Salt Lake, which was a marshland, has become an exurb, and the city has expanded into Rajarhat-Newtown where, too, many water bodies have been filled up for building concrete structures. Thus, there is no place for most of the city’s storm water to drain out to.

Even the East Kolkata Wetlands, a Ramsar site, is being encroached upon surreptitiously by land sharks.

Unplanned Growth

Since 1947, and especially after the early 1970s when tens of thousands of hapless refugees from the then East Pakistan fleeing religious persecution flooded into Kolkata and settled down in the city and its outlying areas, the city’s growth has been totally unplanned.

Slums came up all over the city and new middle and lower middle class townships mushroomed, especially in the southern, eastern and northern fringes, without proper drains and sewers. These are the areas that remained submerged for 48 hours and more after last weekend’s downpour.

Siltation Of Hooghly

Heavy siltation has drastically reduced the carrying capacity of the Hooghly river. Dredging is mostly perfunctory and even so, it is impossible to pump out the city’s storm water to the Hooghly when it gets swollen during high tide.

Given all these factors that cause waterlogging, it is quite certain that Kolkatans have to resign themselves to remaining under water after every heavy downpour for a few hours, at least in the immediate future.

Installing more pumps, as is often demanded, won’t solve the problem at all. Only dredging the Hooghly to increase its carrying capacity, foregoing the use of plastic, cleaning all clogged canals and creating more waterbodies can mitigate the waterlogging woes of Kolkata.