KARACHI: The city needs strict monitoring to completely prevent any development that obstructs the path of floodwater entering rivers/storm-water drains, which should be regularly de-silted and maintained. Besides, there is an immediate need to carry out a flood path study that must take into account the natural features, existing and proposed physical developments and drain channels in the city.

These suggestions were put forward by seasoned architect and urban planner Dr Noman Ahmed while speaking to Dawn about what the government needs to do in the aftermath of recent rains to prevent flooding in the city.

“The study may be conducted by hydrologists and other related experts to establish the path of the flood. Mathematical modelling around various anticipated quantities of floods may also be done to provide finesse to this exercise,” said Dr Ahmed.

Explaining Karachi’s topography and the city’s vulnerability to flooding, he said that the north, north-east and eastern edge of Karachi comprised series of longitudinal hills and valleys.

The spatial terrain where the metropolis was located comprised low-lying hills stretching all the way into the south, up till the coast.

“The north-west of Karachi is bound by the Hub River valley and the hills of Lasbela district in Balochistan. Due to this surrounding undulating topography, the possibility of rainwater gushing towards the city gets enhanced,” he said.

In this respect, he referred to the recent rains in which rainwater collected in the vast and largely uninhabited suburbs and then moved towards the neighbourhoods that were located along the fringes of the city. “The water moved largely from the north and north-east towards the south in expanded volumes. Wherever the natural topographical connection with the natural outfall was obstructed due to a settlement or another type of development, it caused damage,” he pointed out.

Rainwater harvesting

Asked how the city could harvest rainwater, Dr Ahmed emphasised the need to learn the wisdom of traditional farmers who developed natural ditches into small-scale reservoirs and made such paths that led the rainwater enter into those reservoirs.

“This locally stored water enabled the local agriculture to survive in relatively dry years when rain was less. In built areas, underground tanks can be created which can store the water accumulated on the roofs through an integrated piping system,” he said, adding that this water could serve the domestic gardening and other similar purposes.

He described filling of Lath and Thaddo dams in recent rains as good news for farmers, though few were now left due to enormous land-use change.

“Efforts should be made to designate such locations as permanent reservoirs with a moratorium on land-use change. The land allocated for a reservoir must not be altered at all,” he said.

Responding to a question as to why some newly developed housing societies built on the routes of natural drains remained safe in the recent rain spell, he said these residential developments were done by altering the existing levels of the regional topography.

“Many of these developments were done after a massive cut and fill exercise where the levels of development were relatively raised from the surroundings.

“A regional levelling study may also be done to establish the level benchmarks for facilitating flood prevention and guiding the floodwater to rivers without any obstruction,” he noted.

Relying to a question about areas like Scheme No. 33 (Gulzar-i-Hijri) spread over 26,000 acres, which remains prone to flooding, he said the intent and purpose of this vast scheme launched by the Karachi Development Authority in 1965 along the Superhighway was to allocate land to registered cooperative societies formed by various employees’ welfare and other similar organisations.

“Due to enormous time lag between the allotment of societies, internal management discords within various societies and poor quality development of internal and external infrastructure, this development could not become attractive for the middle classes of the city,” he said, adding that under this scheme only land was allocated and no provision was made to protect natural drainage routes.

Published in Dawn, August 16th, 2019