KARACHI: The Sindh High Court on Wednesday directed all stakeholders, including the management and residents of the Defence Housing Authority, to find out a mutual solution in the light of suggestions/recommendations made by engineering experts of the NED University of Engineering and Technology and the DHA to improve the existing and proposed drainage system in the upscale neighbourhood of the metropolis.

The bench also directed the DHA residents to propose experts and seek their assistance in coming up with “practical solutions at their sole cost”.

It further said that the first proposed meeting be convened within the seven days, and the follow-up meetings may be conducted within the next 30 days.

The bench adjourned the case for six weeks, directing the parties to submit a report in this regard by the next date, said the residents’ counsel Barrister Mohsin Shahwani.

A two-judge bench headed by Justice Syed Hasan Azhar Rizvi issued these directives while hearing a petition about the sewerage infrastructure that caused flooding during the torrential rains in DHA and CBC in 2020.

It may be recalled that in September last year the SHC had directed the NED University to conduct an evaluation of the drainage infrastructure within the jurisdictions of the CBC and DHA and also asked the two institutions and the petitioners to provide requisite information and documents to the vice chancellor of the university.

On the last hearing, the NED University of Engineering and Technology had submitted a report about evaluation of the drainage infrastructure in the DHA stating that existing design would be inadequate if storm-water drainage system was also used for sewage disposal.

The report suggested that sewage must be drained out separately to get maximum benefit from the existing and proposed drainage system in future.

It further said that sewer water and deposition of solid waste had reduced the capacity of storm-water drains and warned that more inundation was possible at hotspots and in overall areas of DHA and Cantonment Board Clifton.

It recommended in the report that major drains were clogged due to sewage flow and solid waste, which required a regular cleaning and maintenance to ensure drainage of storm-water in future.

“It is also important to mention that the simulations made in this vetting study and in the design report, the amount of inundation is still underestimated because model has the assumption that drains are empty at the start of rainfall; therefore, the amount of drained water from the area could be a lot less than shown as discharge. Consequently, more inundation is possible at the hotspots and overall in the area,” the report had cautioned.

The report further said that even at a 10-year return period, with no sewage flow in the existing drainage system, a total of 15 manholes were found inundated for more than one hour with the spread of water at pavement greater than standard six feet and depth at curb exceeding six inches.

Referring to the recent heavy monsoon rains that caused urban flooding across Karachi, the NED report stated that the current rainfall warranted the use of a return period larger than 10-year as Karachi was witnessing a recurrence of rainfall events like 2020 and 2022, and suggested to use at least a 50-year return period rainfall intensity for redesigning of the storm-water drainage system, which is also supported by international design criteria and guidelines.

“Part 4 of SWD Plan 2007, which was the Sewerage Master Plan for DHA, must be implemented by authorities to ensure no [flow of] sewage into the existing drainage system (SWD Plan 2007),” the report further recommended.

It said that the extreme flooding conditions in 2020 and 2022 in Karachi in general and DHA in particular were the recent examples of flooding due to lack of planning and maintenance of storm-water drainage system of a cosmopolitan city.

The NED varsity in its report said that floodwater accumulation was also related to solid waste management and it had tendency to clog the drainage system if not removed accordingly while another possible problem was that Karachi was using same infrastructure for both sewerage and storm-water drainage.

It stated that the main objective of this study was to vet the “Construction of leftover storm-water drainage network in Phase-I to VIII, DHA Karachi design validation” for improvement of existing/suggested drainage system.

Published in Dawn, September 15th, 2022