rom an oppressive heatwave that tormented the people to heavy rains that bring to mind the familiar threat of urban flooding, Karachi has become a microcosm of climate change exacerbated by unplanned urbanisation.

Sindh Provincial Disaster Management Authority weather forecast says that more than 100 per cent more rains are expected in July and August.

Talking to TNS, chief meteorologist, Dr Sardar Sarfraz, says that urban flooding occurs when a large amount of rain falls within a short time span, say one or two hours. If the same amount is spread over 24 hours, the rainwater drains away easily.

“Theoretically speaking 80 mm-100 mm of precipitation in one hour can create serious problems in Karachi. If the same amount is spread out over a whole day, no harm is likely,” says Dr Sarfraz.

“In Karachi, the mean July rainfall is 53.2mm, August precipitation 64.6mm and September 23.6mm. This time around there is a higher probability of beyond-normal rains in Karachi and the southern districts,” he cautions.

This is reminiscent of one of the worst crisis the city experienced in the aftermath of 2020 rains that flooded large parts of the city.

The 46 major and 500 minor storm drains that are heavily clogged, blocked and encroached on cannot accommodate torrential rain. Over the years this has brought Karachiites to a point where hardly anyone gets to enjoy the rain. Instead, the citizens worry about the possibility of urban flooding.

“Karachi’s storm drains and nullahs can sustain only low-to-moderate rains. A medium-to-high rainfall is bad news,” says Dr Noman Ahmad, dean of architecture and sciences at the NED University. However, he adds a caveat; “…the management of low-to-moderate rains is entirely dependent on periodic desilting of the beds and channels flowing into these drains.”

The much-anticipated rains that break the heat spell are seen by most Karachiites with consternation. Over the years, the spectre of hours of traffic snarls, the possibility of wading through stagnant pools on most roads while worrying about a snapped electricity wire or an open manhole or caved-in roads is too horrifying to allow any pleasant thoughts.

Against this backdrop, Mayor Murtaza Wahab says that the necessary preparations have been made to prevent urban flooding this year. He says that the drainage of rainwater has improved a lot with the removal of encroachments and clearance of bottlenecks around Gujjar and Mehmoodabad nullahs.

The mayor tells TNS that Karachi Metropolitan Corporation has undertaken the de-silting of 46 major drains and 500 minor drains. “The provincial cabinet provided Rs 250 million for the purpose,” he says.

The sludge and muck removed from some of the drains is still piled along the drain banks. The mayor is hopeful that the exercise will be completed ahead of the rains. He says staff, machinery and pumps will be dispatched to keep the major roads clear and ensure rainwater drains away from all towns.

Regarding illegal settlements constructed on the drains, Murtaza Wahab says “Encroachments from other storm water drains will also be removed to ensure smooth drainage in the future.”

Kiran Khan, a local media person, criticises this ritualised cleaning ahead of the monsoons instead of “…of an ongoing, year-long process to spare the city of the recurring torment.”

This brings us to the heart of the problem: the development projects that leave the topography topsy-turvy, “…disturbing and disrupting the natural drainage pattern. “ Dr Noman Ahmad explains, “Every time road building, repairs and real development projects are taken up, they pose connectivity issues for the houses and the side lanes. As a result, the rainwater gets trapped.”

The much-anticipated rains that break the heat spell are seen by most Karachiites with consternation.

Karachi has a high population density (>20,000 people/sq km) spread over an area of 3,600 sq km. Years of neglect, poor infrastructure, weak institutions, political-ethnic conflict and unchecked, unsustainable urban sprawl have made the city even more vulnerable to climate change effects.

The storm drains are teeming with illegal settlements that have largely blocked their flow causing almost annual flooding of adjoining neighbourhoods. Gujjar nullah, Orangi nullah, Mehmoodabad nullah, Lyari nullah, Manzoor Colony nullah and Malir nullah are the major drains that routinely overflow giving the city the look of a giant cesspool. The city has witnessed at least five episodes of catastrophic urban flooding in 2006, 2011, 2012, 2013 and 2020.

The worst disaster struck in 2020 when on August 27, it rained 230mm in 24 hours. That inundated large parts of the megapolis. Besides, the loss of life and massive property damage, the city resembled a giant stinking sewer.

The situation forced an abrupt reawakening for the administration and government. The PTI-led federal government announced a Rs 1,100 billion Karachi package and tasked the National Disaster Management Authority, the Frontier Works Organisation and the National Logistics Cell to clean the Gujjar, Orangi and Mehmoodabad nullahs, besides the DHA storm drain. The plan was to deepen and widen them, construct box culverts, install stormwater channels and sewer lines and build a road and pavement to prevent any new settlements.

The Manzoor Colony nullah, which discharges into the sea had been reduced to 8-14 feet, from its original 100-200 feet width and was heavily clogged and silted. This was before the widening project was finally taken up in 2021. The knee-jerk reaction saw the ruthless demolition of up to 12,000 homes, evicting 96,000 people ‘overnight’ without any resettlement and rehabilitation plan. This led to the suspension of the campaign on the orders of the superior courts. Even the UN took notice.

Come 2024, experts fear that despite the improvements, the nullah is still congested. The shops along its banks have taken over pedestrian space and the drain remains prone to solid waste dumping. Its exit into the sea also needs desilting. The case study is illustrative.

The 2020 rains did not spare the Defence Housing Authority (. The DHA Storm Water Drain Project, a 74km drain is under construction four years on.

The projects to fix the problematic nullahs have somewhat addressed the immediate issue but the inherent design flaws have created some more issues. According to Dr Noman, while the Manzoor Colony project has improved the natural flow, it is not aligned with the perpendicular streets that used to open in the nullah.

“While the project has addressed the immediate problem of flooding in a particular area, the real benefit of this intervention will only be achieved when it is aligned with adjoining lanes and streets of the neighbourhood. The same has happened with the Orangi and Mahmoodabad nullahs. Rainwater inflows into the nullahs have to be ensured by making adjustments in flow levels and removal of physical barriers,” he says.

“The city is riddled with projects that have disrupted the natural drainage pattern. Real estate development along the M 9 (Super Highway) ignored the basic principle. As a result the Thado Dam breaches flood the critical artery connecting Karachi with upcountry for hours every year,” says Dr Noman.

A similar problem resulted from the construction of the retaining walls of the Lyari Expressway in the middle of the channel. Dr Noman says instead of using pillars for the purpose, as advised by experts, a retention wall was built. It not only obstructed the natural flow but also caused ‘needless’ eviction of a large population living near its banks. Not only did it multiply the cost of the project but “…to this day the banks of the channel regularly flood during rains,” he says. Upon completion, the upcoming Malir Expressway is feared to pose similar problems, obstructing the natural flow of flood waters.

Karachi urgently needs to upgrade its drainage infrastructure to mitigate the looming climate change threats. Effective solid waste and sewage management are also crucial. Only a revamped system can keep it afloat.

The contributor works for The News International