Treat Delhi’s natural drains as waterways

By: | Published: August 1, 2018 1:34 AM

As pressures of urbanisation lead to greater concretisation in our cities, we need to work harder to rejuvenate our urban water bodies, use parks and green spaces for rainwater harvesting.

Treat Delhi’s natural drains as waterways (Illustration: rohnit phore)

This is the time of the year when Delhiites suffer floods, and often know not what to do and who to blame because the multiple government authorities are busy pointing fingers at each other. Monsoon used to be the season when my generation, as children, used to look forward to a respite from the scorching heat of summer. Now, we protect our children from waterlogged areas in the city, worried that much of the water on the ground may well be mixed with sewage.

A long-awaited report on How to Make Drainage Work in the National Capital Territory of Delhi, prepared by Prof AK Gosain and his team from IIT Delhi, has just been submitted to the Department of Irrigation and Flood Control of the government of Delhi. The contributors to the study include ‘insiders’, i.e. people from municipal corporations, Public Works Department (PWD), Irrigation and Flood Control Department, Delhi Jal Board (DJB) and Delhi Development Authority (DDA). The report spells out what is needed to ensure that the drainage system in Delhi works efficiently.

There are three major drainage basins in the NCT of Delhi, i.e. Najafgarh, Barapullah and Trans-Yamuna basins, and there are 22 natural drainage systems in these basins which outfall into Yamuna somewhere during its 46-km run through Delhi. There are 201 sub-segments of the natural drains in these networks. These ‘drains’ are actually the waterways that carry the run-offs from the plains to the river Yamuna, and also recharge groundwater and support biodiversity. Calling them natural drains that provide safe exit to storm water, including flood waters, understates their ecological significance.

The IIT team reports that many of these channels/drains have been encroached and are disappearing; 19 out of the 201 natural drains in the 1976 Master Plan cannot even be traced today. Of the rest, some are filled with solid waste and sometimes construction debris; others are carrying sewage and hence functioning as sewers.

The IIT team did not have all the necessary data and had to take recourse to interpolation and engineering judgement on cross-sections and invert levels of drains, flow directions, outfalls, etc, to conduct simulations of the storm water management model for each of the three basins. Armed with these simulations, they have come up with detailed recommendations on how to make Delhi’s drainage work. They have looked at large drains (4 feet and deeper), while drawing attention to the importance of other drains being functional for the system to be efficient. City managers also need to evaluate the road system in the city for design flaws that might be aggravating water-logging problems.

The recommendations that emerge from the complex exercises in the IIT report are very simple and doable. The major ones are discussed below:

(i) No encroachment of any storm water drain should be allowed. Special drives must be conducted to remove existing encroachments. It would require tremendous political will to implement this recommendation. A typical pattern seems to be first to use the open drain as garbage dump and then, with the passage of time, clear the dump, cover the drain and use the area for the purpose of building a market or a bus depot or any other urban amenity, thus sacrificing the resilience of the city. A lot of wrongs that have been done will have to be undone. The public and the media should highlight encroachments as they begin, to prevent their completion.

(ii) No construction should be allowed inside any storm water drains. Two egregious examples of violating this principle are laying utilities inside the storm water drains and building pillars of elevated roads/metro inside the drains.

(iii) The sewerage network should be totally separated from the drainage network. Only storm water and treated sewage of acceptable quality as per the norms of the Central Pollution Control Board should be allowed in the storm water drains. Thanks to a ruling by the National Green Tribunal (NGT) in 2015, DJB has come up with a Master Plan for interceptor sewers to trap the sewage coming out of unsewered and unauthorised colonies, and to take the same to the nearest sewer line rather than dumping it in the nearest storm water drain. They are working to implement the plan by December 2018.

However, in the areas which are connected to a sewerage network, DJB has for years been following a practice of puncturing sewer lines and draining sewage into storm water drains in the event of blockage. The recommendation of the IIT team is that this must be explicitly forbidden and that DJB should use other available equipment for de-clogging the sewer lines.

(iv) No solid waste or garbage is to be allowed to be dumped into storm water drains, for example Pankha Road (‘Choking the city’, The Indian Express, August 31, 2016; goo.gl/imn4dN). Not only is this a public health hazard, but it also provides temptation to cover the drain with the passage of time, as happened in Defence Colony and South Extension, among other places. The NGT order of March 2014 on river Yamuna rejuvenation and a Policy Statement by Delhi government in response to directions from the High Court of Delhi, specifically prohibit covering any natural storm water drain in the city.

(v) No silt from the road (before or after road sweeping—manual or otherwise) should be allowed to be dumped into the bell-mouths that lead to drains on the side of the road. The report emphasises that this would require a complete overhaul of the road sweeping process and suggests a monitoring mechanism to ensure compliance.

(vi) No construction and demolition (C&D) waste should be allowed to be dumped into storm water drains, and further that the amount of waste from a construction site should be estimated in advance and lifted by government-appointed contractors for dumping at C&D processing sites. This is also likely to be resisted by developers and builders, and enforcement must be taken up on a war footing.

(vii) Access points for covered drains must be provided at appropriate distances so that de-silting of drains can be carried out regularly. Most of the covered drains currently do not have access for de-silting. The report recommends that a schedule of de-silting should be displayed in a manner that is understood clearly by general public.

There are many more recommendations. The problem arises because there are multiple government departments involved, with overlapping responsibility and no clear accountability. The storm water drains are under the jurisdictions of the different municipal corporations, PWD or the Irrigation and Flood Control Department, depending on their size. The sewerage network, on the other hand, is the responsibility of DJB.

Whether or not there is a single institution responsible and accountable for drainage management as recommended by the report, it is clear that there is an urgent need for strong coordination across departments and fixing accountability at every level. We also need a mechanism for public oversight and prompt remedial follow-up.

Finally, as pressures of urbanisation lead to greater concretisation in our cities, we need to work harder to rejuvenate our urban water bodies, use parks and green spaces for rainwater harvesting, and also use bio-swales to manage and filter the storm water run-off.

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