Turning the tide: How to revive Dhaka’s canals and fix waterlogging

Throughout this month, we have published six reports on Dhaka's canals, detailing how these water bodies, once the lifeblood of the capital's drainage system, are now clogged, encroached upon, and reduced to narrow, polluted channels.

Many canals have completely disappeared, replaced by roads and structures. This in turn has put the city's draining system into disarray, with the capital drowning every time it rains above a certain threshold. People even die in the waterlogged streets of Dhaka, coming in contact with live wires underneath or simply drowning.

Without immediate and sustained intervention, the waterlogging crisis will worsen, as climate change means the city may experience unusually high rainfall anytime -- already seen in many places near Dhaka this year, according to experts, policymakers, and planners.

THE EXTENT OF THE PROBLEM

Over the years, Dhaka has lost significant canal space due to unchecked encroachment. Major water bodies have been filled, converted into box culverts, or obstructed by infrastructure projects.

Syeda Rizwana Hasan, adviser to the environment ministry, said, "Canals formed the natural drainage system of this city. Regrettably, we lost most of them due to urbanisation, conversion into culverts, and encroachments."

"Then there is pollution. Sewage and industrial effluents are discharged into the canals in a manner as if they are meant to be used as private drainage. Added to this, solid waste and plastic clog the waterways, further obstructing their flow," Rizwana said.

Mohammad Azaz, chairman of the River and Delta Research Centre, said, "Dhaka was a wetland city, but it should have been a sponge city. Due to unplanned urbanisation, we no longer have spaces to retain water for a certain period."

RECOVERING, PROTECTING CANALS

At the heart of reviving Dhaka's canals lies the need to recover encroached areas and establish clear demarcations based on CS and RS maps. Authorities at both the Dhaka North City Corporation (DNCC) and Dhaka South City Corporation (DSCC) have finally begun addressing this critical step.

Md Mahmudul Hasan, administrator of DNCC, said, "We are demarcating 29 canals and setting up pillars to prevent further encroachment. More than 1,000 pillars out of 1,100 have already been set up, and the rest will be completed by December. The army is implementing the project."

Meanwhile, the chief engineer of DSCC, Md Aminul Islam, said they have decided to earmark the boundaries of canals based on CS maps, a step that had not been undertaken earlier.

"We will apply it in the project to develop four canals, which have already been approved by the Ecnec. The design that was prepared earlier did not consider the demarcation of CS maps. As a result, residents on both sides of the canals slowed down the project by creating obstacles," he explained.

"In a recent meeting, it was decided to consider only CS maps during the demarcation of the canals, and the canals will be dug up accordingly," Aminul said.

"If we find even a person with legal documents within the alignment of the canal, we will remove them through due process," he added.

Meanwhile, the Executive Committee of the National Economic Council (Ecnec) on October 11, 2022, approved a Tk 898.73 crore project to revive four canals -- Kalunagar, Jirani, Manda, and Shyampur -- to alleviate Dhaka's chronic waterlogging woes.

Aminul said the work has already started, and they are hopeful to complete the project by February 2026.

While such efforts are promising, experts argued that authorities must take tougher measures against encroachers and ensure accountability.

Adil Mohammad Khan, president of the Bangladesh Institute of Planners (BIP), said, "Vested interest groups that destroyed flood flow zones for housing or industries must be penalised. Culpable officials from Rajuk, the Department of Environment (DoE), and other government offices should also face consequences."

Environmental laws must be strengthened to ensure no one dares to encroach flood flow zones, he said.

Connectivity between different canals, water bodies and water channels with flood flow zones should be restored, he added.

ROLE OF FLOOD FLOW ZONES, RETENTION PONDS

Dhaka's canals do not operate in isolation. Retention ponds and flood flow zones play a vital role in holding excess water and maintaining the natural flow. However, these lifelines have also fallen victim to neglect and encroachment.

At Kalyanpur, a retention pond meant to safeguard Mirpur and adjacent areas from waterlogging has been reduced to just a fraction of its recommended capacity.

Originally designed for 514 acres, only 53 acres have been secured over three decades.

"We will increase the area of the retention pond," DNCC administrator Mahmudul said.

"We are cleaning floating plastic waste and increasing its depths to increase the retention capacity. This project is ongoing, and we hope it will be completed within the next five or six months," he said.

Meanwhile, Adil Mohammad Khan urged strict protection of flood flow zones, saying, "Any development must be completely restricted in these zones. Main flood flow and sub-flood flow zones should be merged under the Detailed Area Plan (DAP) to safeguard them."

TURNING BOX CULVERTS BACK INTO OPEN CANALS

One of the most controversial decisions in Dhaka's drainage history was the conversion of canals into box culverts. While initially seen as a solution to waterlogging, they have proven ineffective. Box culverts quickly accumulate sediment and waste due to poor maintenance, reducing water flow drastically.

Iqbal Habib, vice-president of Bangladesh Paribesh Andolon (BAPA), said, "Box culverts are a faulty design. No country in the world uses this system. The government must turn these back into open canals to achieve lasting results."

Fazle Reza Sumon, convener of the advisory council of Bangladesh Institute of Planners, said box culverts cannot be an alternative to canals as they do not function in the same way.

"Box culverts obstruct natural water flow, leading to gradual sedimentation that reduces capacity over time due to a lack of regular maintenance," he said. "In contrast, open canals allow for better water flow and are easier to clean and maintain."

RESTORING CANAL-RIVER CONNECTIVITY

Reviving Dhaka's canals will also require restoring their connectivity with rivers. Once linked to the Buriganga, Turag, Balu, and Shitalakhya rivers, the canals could seamlessly transport excess water, said experts.

Today, unplanned construction of embankments, sluice gates, and roads has severed these links.

Dr Ainun Nishat, a water resources specialist, called for the revival of circular navigation routes.

"The government must acquire land if necessary to restore smooth navigation and canal-river connectivity," he said.

A HOLISTIC APPROACH

Experts stressed that recovering canals and flood flow zones is only part of the solution. Dhaka's drainage system must also be kept clean and functional.

Dr Akter Mahmud of BIP said, "Protecting retention ponds, recovering canals, and maintaining drainage networks -- both surface and stormwater -- are crucial to reducing waterlogging."

Meanwhile, RDRC Chairman Mohammad Azaz said, "Despite excavation efforts, canals are losing water cover to waste dumping and encroachment. So, protecting what remains is far more critical than digging new ones."

PROMISING INITIATIVES

While challenges abound, there are signs of progress. DNCC's plans for a hydro-eco park at Kalyanpur envision a retention pond surrounded by trees, increasing water-carrying capacity while maintaining ecological balance.

Similarly, DNCC's projects to develop canals like Bounia and Sangbadik Colony include excavation, walkways, and improved vehicular movement.

However, regarding boat communication, Mahmudul said it is still possible from Rampura TV station, but he is not sure whether they will be able to create a boat communication network across all the canals as the widths of many canals are insufficient.

Meanwhile, Adviser Syeda Rizwana Hasan remains cautiously optimistic about the interim government's plans to recover canals and create a blue network -- an interconnected system of canals, rivers, and water retention areas designed to improve drainage and restore natural water flow.

"We are anticipating a final work plan by December and hope to kick off implementation in the new year," she said.