Why Bangladesh urgently needs a heat disaster management plan

One of the most significant impacts of climate change in the modern world is the abnormal rise in temperature in urban areas. In Bangladesh, as well as in many developing countries around the world, rapid urbanisation, concrete-based infrastructure, and unplanned construction are causing cities to become increasingly warmer. 

This phenomenon is known as the "Urban Heat Island" (UHI) effect, where urban temperatures remain significantly higher than those of surrounding rural areas. Recent studies have shown that urban architectural patterns, building density, road structures, and the amount of greenery directly influence urban temperatures.

As heatwaves grow more frequent and intense, Bangladesh's rapidly expanding concrete cities are turning into dangerous heat traps. Researchers warn that without climate-responsive urban planning, greener infrastructure and urgent heat action plans, urban heat could evolve into a major public health and economic crisis.

What the research shows 

According to research findings, the Urban Heat Island effect is not solely a consequence of climate change; rather, it is deeply connected to the human-made built environment. Materials such as concrete, asphalt, and glass absorb solar heat rapidly and retain it for long periods. During the day, these materials absorb excessive heat and gradually release it at night, preventing the urban environment from cooling down. In particular, high-rise buildings and narrow streets obstruct air circulation, which further increases urban temperatures. This phenomenon is referred to in research as the "Urban Canyon Effect."

In the context of Bangladesh, this problem is even more evident. A study conducted on Dhaka city found that during heat waves, the Urban Heat Island effect becomes more intense, and temperatures inside the city remain much higher than in surrounding areas. Due to rapid urbanisation, open spaces, water bodies, and greenery in Dhaka have decreased significantly. At the same time, the growing number of concrete-based high-rise buildings is obstructing natural ventilation. As a result, urban residents are experiencing heat-related discomfort both day and night.

A recent study by Abeda Tabassum revealed that over the past 25 years, the intensity of Dhaka's Urban Heat Island has shown an increasing trend, rising by 0.21°C per decade. The average UHI intensity in Dhaka is 0.48°C. Seasonally, UHI is highest during winter (0.95°C) and lowest during the monsoon season (0.23°C). In all seasons, the UHI effect is strongest at 9:00 PM local time. 

A recent study by Abeda Tabassum revealed that over the past 25 years, the intensity of Dhaka's Urban Heat Island has shown an increasing trend, rising by 0.21°C per decade. The average UHI intensity in Dhaka is 0.48°C. Seasonally, UHI is highest during winter (0.95°C) and lowest during the monsoon season (0.23°C). In all seasons, the UHI effect is strongest at 9:00 PM local time. 

Dhaka's daily maximum average UHI intensity reaches 2.15°C. The study also found that the frequency of heat wave events in Dhaka during the monsoon season has increased significantly, rising by 5.8 days per decade. In Bangladesh, heat waves are generally associated with anticyclonic circulation and high-pressure anomalies in the middle and upper troposphere during the pre-monsoon season and with similar anticyclonic circulation and pressure anomalies in the lower and middle troposphere during the monsoon season. 

During heat waves, UHI intensity increases further during both day and night in the pre-monsoon season and mainly at night during the monsoon season. Reductions in relative humidity and cloud cover further strengthen the interaction between UHI and heat waves.

The impact of heat stress 

Heat stress has profound impacts on human health and daily life. Excessive heat increases the risks of heatstroke, dehydration, high blood pressure, respiratory problems, and cardiovascular diseases. Research also indicates that the Urban Heat Island effect can negatively affect mental health. 

Children, the elderly, and low-income populations are the most vulnerable to these risks. People who work outdoors, such as construction workers, rickshaw pullers, and agricultural labourers, are especially exposed to severe health hazards due to prolonged heat exposure. Excessive heat also reduces work efficiency and negatively impacts economic productivity.

What needs to be done 

To address this problem, architecture and urban planning have crucial roles to play. Research suggests that reducing building density, properly regulating building height and arrangement, and ensuring adequate greenery can significantly lower urban temperatures. Building placement should be designed in a way that allows natural airflow to circulate easily. Likewise, high ceilings, verandas, sun-shading systems, and cross-ventilation can help maintain lower indoor temperatures.

At present, "cool roof" technology is considered an effective method for reducing urban heat. Reflective-coloured roofs absorb less solar heat and reduce indoor temperatures. Studies have shown that using light-coloured materials and heat-reflective surfaces can significantly lower urban temperatures. 

Similarly, green roofs and vertical gardens play important roles in temperature regulation. Vegetation creates shade and reduces heat through evaporation and transpiration processes. Researchers have emphasised that increasing urban greenery is one of the most effective ways to reduce the Urban Heat Island effect.

The selection of building materials is also extremely important. The increasing use of concrete and asphalt in most cities has raised the level of heat absorption. Research suggests that using materials with lower heat absorption and higher reflectivity can help keep urban environments comparatively cooler. 

Traditional Bangladeshi architecture used natural materials such as earth, bamboo, and other local resources, which naturally supported thermal comfort. Reintroducing this local knowledge and climate-responsive design into modern architecture is now a necessity.

Integrated initiatives are essential in urban planning. Research indicates that preserving parks, playgrounds, water bodies, and open spaces can effectively reduce urban temperatures. Planting trees along roadsides, creating shaded pedestrian corridors, and preserving ventilation corridors can help cool cities. 

At the same time, reducing excessive building coverage ratios and maintaining sufficient open spaces within urban areas are necessary. Under such planning, it is also important to implement early heat warning systems through the meteorological department, ensure emergency medical preparedness in hospitals and healthcare centers, establish adequate shaded rest areas in urban zones, and conduct public awareness campaigns. Special guidelines should also be enforced in schools, workplaces, and construction sites during heat waves.

Government initiatives are equally important in this regard. Climate-responsive building codes, incentives for energy-efficient construction, and urban greening programmes must be implemented. At the same time, comprehensive heat action plans and public awareness measures are urgently needed to combat heat waves. Through research- and technology-based urban planning, future cities must be made more livable and heat-resilient.

In conclusion, the Urban Heat Island effect is no longer just an environmental issue; it has become a major challenge for public health, the economy, and urban life. Unplanned urbanisation and concrete-dependent architecture may intensify this crisis in the future. Therefore, adopting sustainable architecture, environmentally friendly urban planning, and science-based policies is now the greatest necessity for building a cooler, healthier, and more sustainable urban environment.

Professor Sajal Chowdhury is an architect, educator and head of the Department of Architecture, CUET and a researcher focusing on Environmental Experience Design, IEQ, Architectural Science and Wellbeing.