Professor Dr Muhammad Rashidul Hasan, Dean of the Faculty of Urban and Regional Planning at Chittagong University of Engineering and Technology (CUET), speaks to The Daily Star about the planning failures behind Chattogram's recurring floods, the costs of losing wetlands and hills, and why the city's future depends on restoring, rather than replacing, its natural systems.

The Daily Star (TDS): Every year, even moderate rainfall causes waterlogging in Chattogram. The recent spell of continuous rain, however, made the situation particularly severe. Why does the city remain so vulnerable to flooding?

Muhammad Rashidul Hasan (MRH): We must begin with Chattogram's topography. The city is surrounded by hills, many of which have loose, sandy soil. During the monsoon, rainwater washes sand and sediment down these slopes and into the city's drainage network.

The problem has worsened because the hills have been cut indiscriminately over the years. Unplanned urbanisation and the destruction of vegetation on the remaining hills have made the soil more vulnerable to erosion. Every spell of heavy rain now carries large quantities of sand into drains, canals and other natural waterways.

The second major factor is rapid and poorly planned urbanisation. This is not unique to Chattogram, but its consequences are particularly visible here. Water-retention areas, agricultural land and wetlands on the urban periphery have been filled or converted without regard for their ecological function.

In the past, these areas temporarily stored excess rainwater during the monsoon. As they have gradually disappeared, water has lost the spaces in which it could collect before draining away. It therefore accumulates in built-up areas, where there are few natural outlets.

Although several drainage projects have been undertaken in Chattogram, their effectiveness is being undermined by sediment and waste. The city generates around 3,000 tonnes of solid waste every day. According to the city corporation, it can manage roughly 2,000 tonnes. This leaves a substantial amount of waste uncollected, much of which eventually ends up in drains, canals and other water bodies. Consequently, the drainage system loses capacity day by day.

Chattogram also differs from many other cities because its drainage water is supposed to flow naturally into the Karnaphuli River. However, the river has not undergone adequate capital dredging for many years. Its bed has become increasingly silted up and elevated.

During high tide, river water can flow back into the city's drainage network. At other times, water trapped within the city cannot be discharged efficiently into the river. Waterlogging becomes severe when these factors, including sedimentation, waste, the loss of wetlands, inadequate drainage, and tidal backflow, operate simultaneously.

This year's flooding became especially extensive because the rainfall itself was exceptional. According to the available records, Chattogram received its highest rainfall in 42 years. The pattern was also highly unusual: June recorded very little rain, while just four days in July produced enough rainfall to break a four-decade record.

This abrupt shift from unusually low rainfall to extreme precipitation reflects the increasingly erratic weather associated with climate change. When such rainfall falls on a city whose natural drainage system has already been weakened, the consequences become disastrous.

The conditions outside metropolitan Chattogram, particularly in southern Chattogram and Cox's Bazar, are somewhat different. There, the declining navigability and water-carrying capacity of rivers such as the Sangu and Matamuhuri have prevented water flowing down from the hills from draining away quickly.

Natural drainage channels have also been obstructed by embankments constructed for fish farming, some built legally and others illegally. At the same time, hills continue to be cut at night across large parts of southern Chattogram. Rain then washes sand from these exposed hills into rivers, canals and low-lying areas.

There is also concern that the construction of the Chattogram–Cox's Bazar railway has obstructed some of the region's natural drainage routes. Proper research is needed to determine the extent to which the railway alignment has disrupted water flow. 

A broader problem is the fragmented way in which development has taken place. Chattogram has both a general master plan and a drainage master plan, yet development projects have often been implemented in isolation, without adequate coordination.

The drainage project, worth roughly Tk 12,000 crore, for example, introduced sluice gates and several other new components. But operating these gates properly has become a major institutional and technical challenge in itself.

TDS: The Chattogram Development Authority prepared the city's drainage master plan, but other agencies, including the city corporation and WASA, have been implementing separate development projects. Has this fragmented approach created conflicts on the ground?

MRH: Soon after the Chattogram Development Authority (CDA) was established in 1961, a master plan was prepared for the city. Another master plan was developed in 1995, including a detailed drainage plan. A new master plan is now being prepared as a continuation of that process.

The 1995 drainage plan proposed an integrated system of primary, secondary and tertiary drains, with clear connections between them. It also identified four new canals that needed to be excavated to accommodate future urban expansion. Their alignments and estimated costs were clearly specified.

Unfortunately, these proposals were never implemented with the seriousness they required.

A development authority may prepare a citywide master plan, but it cannot implement every component on its own. Responsibility must be shared among all the relevant public agencies.

The CDA may prepare the overall plan, but the city corporation must implement the components that fall within its mandate. Chattogram WASA, the Bangladesh Water Development Board, the Chattogram Port Authority and Bangladesh Railway must do the same within their respective jurisdictions.

The difficulty is that other government agencies have rarely treated the CDA's master plan as a framework that they themselves must follow. Instead, each institution has implemented its own infrastructure projects piecemeal. The result has been institutional fragmentation and physical systems that do not always connect properly.

Drainage projects are generally implemented by WASA or, in some cases, the city corporation. Chattogram has been a major exception. The CDA itself is implementing the drainage components of the project, worth approximately Tk 12,000 crore.

This has already produced administrative complications. The CDA has said that it wants to transfer the drains to the Chattogram City Corporation once the project is completed. The city corporation, however, has indicated that it may not be able to manage them properly.

A city cannot be improved by addressing a single isolated problem while ignoring its relationship with land use, drainage, transport, housing and the environment. A project designed primarily for immediate political popularity is unlikely to deliver lasting benefits.

It does not have an approved staffing structure adequate to operate such an extensive system. Nor does it currently have the financial capacity to maintain the infrastructure. Managing this new drainage network will also require heavy mechanical equipment and specialised technical support.

The same problem applies to the sluice and regulatory gates. Responsibility for operating some of these gates has been assigned to the city corporation, but its organisational structure does not include the necessary pump operators and technical personnel.

If the drainage system is transferred without sufficient funding, approved posts, machinery and operational support, the city corporation will not be in a position to manage it effectively.

Our concern is that, once construction ends, administrative uncertainty will delay maintenance. The drains may not be cleaned at the appropriate time, and the waterlogging problem could become even more severe despite the enormous investment.

Citizens also have an important responsibility. Public agencies must improve waste collection, but residents must stop using drains to dispose of household rubbish.

Even if the city corporation receives more personnel and modern equipment, no authority can keep the drainage network functional if millions of residents continue to dump waste into it. Institutional reform and behavioural change must therefore proceed together.

TDS: Across Bangladesh, we see canals being occupied, water-retention areas being filled, and environmentally destructive projects being approved for political reasons. Within this culture, what should urban planning look like in theory and in practice?

MRH: Unfortunately, Bangladesh has developed a culture of politically driven development planning. Urban planning is a technical and interconnected process, but decisions are frequently taken to satisfy particular constituencies or produce visible short-term results.

A city cannot be improved by addressing a single isolated problem while ignoring its relationship with land use, drainage, transport, housing and the environment. A project designed primarily for immediate political popularity is unlikely to deliver lasting benefits.

The occupation of canals is not limited to Chattogram; it is a nationwide problem. But one example from Chattogram illustrates how deeply embedded the practice has become. At one point, even a private university had a building constructed on an occupied section of a canal. The structure was eventually removed during the implementation of the drainage project.

Public institutions themselves have sometimes contributed to encroachment. Private individuals and commercial organisations have also encroached extensively on canals and other water bodies.

We have repeatedly argued that simply designating a strip of water as a canal is not enough to protect it. Unless the surrounding space is incorporated into public life, gradual encroachment is likely to continue.

Canal banks should therefore be developed as public green spaces, with walkways, vegetation and recreational areas. When residents regularly use and observe these spaces, illegal occupation becomes much more difficult. A canal integrated into a public park or green corridor is easier to protect than one left isolated behind buildings and boundary walls.

Hill-cutting is equally serious. For years, hills in southern Chattogram have been cut secretly at night, and we are now seeing the consequences.

Because of the region's distinctive topography, exposed hills release large quantities of sand during rainfall. This sediment gradually fills natural drains, canals and other water bodies, reducing their capacity to hold and transport water. Surrounding areas then become inundated. We have even seen sections of the Chattogram–Cox's Bazar highway submerged.

The central problem is not an absence of plans. If you visit the Chattogram Development Authority, the Cox's Bazar Development Authority or the municipalities in the surrounding region, you will find that these risks were identified clearly in their master plans.

The crisis has emerged because government agencies have given too little importance to those plans during implementation. Planning documents cannot protect a city when the institutions responsible for development are free to disregard them.

TDS: Chattogram faces a striking hydrological paradox. It suffers from waterlogging during the monsoon but experiences water shortages in the dry season. What does this mean for the city's long-term future?

MRH: Chattogram has already entered a period of long-term hydrological risk.

Because we have failed to manage freshwater resources properly, saline seawater travels farther upstream along the Karnaphuli River during the dry season. Consequently, the water collected and treated for urban supply contains higher levels of salinity.

At times, the treatment system cannot adequately remove this salinity. Chattogram WASA has therefore had to bring water from the Kaptai area, roughly 70 kilometres from the city, because freshwater sources closer to metropolitan Chattogram have become increasingly saline.

During the dry season, this creates a severe challenge for the urban water supply. The decline in freshwater is also changing aquatic ecosystems and affecting biodiversity.

Freshwater scarcity is no longer merely a service-delivery problem. It is emerging as an environmental disaster. Chattogram faces excessive water mismanagement during one part of the year and too little usable freshwater during another.

TDS: Efforts to address waterlogging still rely heavily on concrete-based "grey infrastructure", such as retaining walls, culverts and drains. Given Chattogram's hills, rivers and canals, what should a nature-based urban planning blueprint look like?

MRH: The drainage project currently being implemented in Chattogram includes silt traps. These are designed to capture sand washed down from the hills at specific points so that it can be removed regularly.

But silt traps address the symptom, not the source. A natural solution must begin with the hills themselves.

Indiscriminate hill-cutting must stop. Tree felling must also be prevented, and vegetation on the remaining hills must be restored. Stable, green hills will retain soil far more effectively and reduce the volume of sediment entering the drainage network.

Second, the Natural Water Reservoir Conservation Act must be enforced. Ponds, wetlands and other water bodies within and around the city should be formally designated and protected as water-retention areas.

Master plans for major Bangladeshi cities have traditionally identified green belts and retention zones around urban areas. Yet industrial establishments and real estate projects have repeatedly filled these areas with sand and converted them for construction.

Even well-managed cities experience temporary waterlogging during extreme rainfall. The crucial difference is that they preserve spaces where water can be stored and maintain routes through which it can eventually drain away.

If Chattogram protects its remaining ponds, wetlands and retention areas, these spaces can absorb and temporarily hold stormwater. They would also help address the urban heat island effect, in which densely built parts of a city become several degrees warmer than their surroundings.

Water bodies and green spaces are therefore not decorative additions. They are part of the city's drainage, cooling and climate adaptation infrastructure.

Rainwater should also be detained at the building level. We have long argued that rooftops and building designs should be able to hold rainfall temporarily. If each building could retain rainwater for even 15 to 30 minutes, the drainage network would gain valuable time to carry away water already on the streets.

Building approval rules should gradually require such measures as part of a transition towards green infrastructure.

At the neighbourhood level, every ward should protect or create small water bodies, playing fields, parks and planted areas. These spaces allow rainwater to infiltrate the soil and help recharge the groundwater table.

Extensive concretisation has made urban surfaces largely impermeable. Water can no longer enter the soil, so it remains on roads and moves rapidly into an already overloaded drainage system.

These issues cannot be addressed separately. Hill conservation, wetland protection, waste management, drainage maintenance, rainwater retention, permeable surfaces, urban greenery and institutional coordination are all parts of the same system.

Only by treating them as an integrated urban and ecological challenge can Chattogram begin to escape its recurring cycle of waterlogging.

The interview was taken by Khairul Hassan Jahin.

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