Experts urge rooftop, vertical gardening to reduce Dhaka's heat

Environmental scientists are encouraging rooftop gardening and vertical gardening on building walls to reduce the urban heat island effect in the capital. 

They said everyone should come forward to promote rooftop gardens in urban areas to reduce the risks of intense heat waves, water-logging and other environmental hazards caused by climate change.

Experts said that to address water-logging, the Rajdhani Unnayan Kartripakkha (Rajuk) must place the highest priority on strengthening its institutional and technical capacity to prevent the filling up or encroachment of floodplains, flood-flow zones and protected water bodies.

Rajuk officials said that if the Climate Resilient Green Action Plan (CRGAP) is successfully implemented at Hazaribagh and Lalbagh, the Green Action Plan could gradually be expanded to other old and climate-vulnerable areas.

Rajuk Chief Town Planner Md. Ashraful Islam told BSS that small-scale urban forestry and tree planting along with canals, which function like the veins and arteries of Dhaka, are needed to reduce the city's temperature. Rooftop gardening and vertical gardening should also be encouraged in densely populated areas. Otherwise, the city will become uninhabitable, he said.

On the other hand, Rajuk Town Planner Mahfuza Akter told BSS that the Purbachal New Town, a mega project, has been developed as the country's first planned green and smart city, where a large lake is being preserved, a central sewage treatment plant (STP) is being established and extensive tree plantation is being carried out.

She said the Rajuk's objective is not merely to control the construction of buildings based on their numbers, but to guide Dhaka's future urbanisation along with a planned, safe and sustainable path. Dhaka is not merely a city; it is the centre of employment and dreams for millions of people.

Ashraful Islam said the risks caused by climate change, including intense heat waves and sudden water-logging, are being felt constantly. Rajuk's core responsibility is to ensure planned land use and develop urban infrastructure capable of addressing these climate risks.

Regarding Dhaka metropolitan city, Rajuk Chairman Md. Reazul Islam said integrated climate and disaster resilient development is being given the highest priority in building a climate-friendly city. 

He said the legal framework for Rajuk's new law and amendments to the building construction regulations has been prepared keeping these two issues in mind.

He said a major obstacle to the development of Dhaka metropolitan city is a lack of coordination. Efforts are being made with all stakeholders, including Wasa and Desco, to clean up the Gulshan-Banani Lake and take action against buildings constructed in violation of regulations.

Town Planner Mahfuza Akter said the Detailed Area Plan (DAP) 2022-2035 is a climate and environment friendly plan. Under the plan, efforts are being made to develop Dhaka as a "blue-green network," combining water bodies and greenery to maintain a sustainable balance between the modernity and nature.

She said flood-flow zones have been identified in the DAP through detailed hydrological analysis and construction of all types of permanent structures has been completely prohibited in those areas. This will help to keep the city's natural drainage system functional.

Mahfuza Akter said all existing ponds, canals, low-lying areas and floodplains within and around Dhaka have been provided legal protection under the water-body conservation policy so that they cannot be filled in under any circumstances. This will increase the city's water-retention capacity and help eliminate sudden water-logging. A blue-green network combining water bodies and linear parks is being developed to regulate the city's temperature and restore biodiversity.

She said all parts of Dhaka do not have the same characteristics and the challenges of historic and densely populated areas such as Old Dhaka are completely different. That is why the Climate Resilient Green Plan (CRGP) was initially adopted with a focus on the Hazaribagh and Lalbagh areas.

The town planner further said the main objective of the CRGP is to restore the vast environmental void created after the relocation of tanneries from Hazaribagh by creating an environment-friendly green belt and open spaces, while increasing climate-adaptation capacity in Lalbagh while preserving its traditional and historical significance. Under the plan, it will be possible not only to reduce climate risks but also to improve the quality of life of local residents and restore the balance of the natural environment.

She said the Urban Resilience Project (URP) has been successfully completed to strengthen Rajuk's capacity and ensure the structural safety of buildings. During the approval of new building designs, every high-rise building is required to have a rainwater-harvesting system and sufficient open space, in accordance with regulations, to allow water to be absorbed directly into the ground.

She said effective measures have been taken to ensure the preservation of water bodies, flood-flow areas and open spaces alongside housing and infrastructure development without hindering economic growth and the development of the housing sector. In the overall development of Dhaka, besides Rajuk, the two city corporations, Dhaka Wasa, the Water Development Board and the Department of Environment are working within their respective legal jurisdiction

Noting that numerous high-rise buildings are being constructed in the capital, Rajuk Chief Town Planner Md. Ashraful Islam said most of the recently constructed high-rise buildings are covered with glass. As these buildings are air-conditioned, they contribute to carbon emissions outside the buildings. The city has lost 8 to 10 percent of its natural water bodies, resulting in a reduced capacity to absorb heat.

He said Dhaka has a history of more than 400 years as the capital city. Although the city has expanded over this long period as far as Narayanganj and Gazipur, no new parks or gardens comparable to Ramna Park.

Suhrawardy Udyan and Zia Udyan have been created. The way out of this situation is to create area-based parks and retention ponds. Energy-efficient technologies and green building materials should be encouraged in the construction of new buildings.