Heavy rainfall is nothing unusual in tropical Malaysia. For many urban residents, however, the sight of dark clouds gathering brings a familiar sense of dread.
Will the roads flood again? Will the drains overflow? And will the journey home turn into another frustrating exercise of navigating jammed and waterlogged streets?
Previously, when the effects of climate change were moderate, conventional flood mitigation strategies were focused on directing excess water away from developed areas through drainage networks, retention ponds and other engineered infrastructure. These systems are still widely used today but experts have highlighted that increasing urbanisation is introducing a host of challenges that requires thinking outside the box.
What if cities could be designed to accommodate excess water rather than simply directing it elsewhere? What if public parks, landscaped spaces and even neighbourhood streets could play an even bigger part in managing heavy rainfall?
A different approach to flooding
This is the thinking behind the concept of sponge cities where urban spaces are designed to absorb, retain and manage rainwater. In Malaysia, one example is Sarawak’s Sibu Cloudburst Masterplan, an initiative that could offer valuable lessons for future property developments.
Sitting along the Rajang River, Sibu is no stranger to flooding. Its low-lying geography, coupled with heavy rainfall and changing river levels, has left parts of the town vulnerable to rising waters over the years.
For residents and businesses, flooding can mean more than the inconvenience of waterlogged roads, with damage to homes, commercial premises and infrastructure adding to the problem.
Flooding has also taken a financial toll on Sarawak. According to the Statistics Department, the state suffered RM61.2mil in flood-related losses in 2025, compared with RM27.4mil the year before. Of that amount, RM32.6mil came from damage to living quarters, putting Sarawak ahead of every other state in this category.
Although the figures cover the whole of Sarawak and not just Sibu, they show how costly flooding can be for homeowners.
Against this backdrop, the Sarawak government, through the Land Custody and Development Authority, engaged international engineering consultancy Ramboll to look into ways to address Sibu’s flood problems.
The resulting Sibu Cloudburst Masterplan takes a different approach to managing excess rainwater. With the planning stage completed in 2024, it is described by Ramboll as Asia’s first city-wide cloudburst planning initiative.
Instead of relying solely on drains and other flood mitigation structures, the masterplan looks at how existing and future urban spaces can help manage water during heavy rainfall.
According to the Sarawak Public Communication Unit, the planning exercise all started with a flood risk assessment covering approximately 39,000 acres, followed by a conceptual cloudburst masterplan that covered 6,700 acres.
The third component focused on an integrated infrastructure and urban redevelopment masterplan for Bukit Assek, covering approximately 815 acres. Central to the initiative is the integration of blue-green infrastructure which combines natural features such as vegetation, wetlands and waterways with conventional engineered systems.
Giving water room to flow
The principle behind sponge cities is pretty straightforward. Rather than allowing rainwater to flow immediately across paved surfaces into drains, urban spaces can be designed to absorb, store, filter or redirect part of that water.
In Sibu’s case, Ramboll’s proposed blue-green infrastructure network includes three wetlands intended to provide stormwater storage while functioning as public green spaces.
Streets could also be designed as cloudburst corridors, incorporating landscaping and permeable surfaces to guide excess water towards designated storage areas. Conventional drainage systems would still be needed but they could work alongside these features to better manage excess rainwater.
This would also allow parks and other public spaces to serve a practical purpose beyond their usual recreational functions.
This approach was also explored at the Malaysia Green Building Council’s (malaysiaGBC) Cities Climate Connect 2026 conference in August, where climate adaptation and nature-based infrastructure featured in discussions about the future of urban development.
At the conference, Ramboll director of sustainable design and climate adaptation Sripragas Nadaraja outlined climate adaptation through three priorities, namely, retrofit, integrate and scale. His approach highlighted how grey infrastructure, such as engineered drainage systems, could work alongside blue infrastructure involving water and green infrastructure built around vegetation and natural processes.
A similar perspective was presented by Henning Larsen Asia Pacific regional director for landscape Jia Xin Chum, who discussed how urban landscapes could accommodate stormwater while supporting biodiversity and providing recreational spaces.
One example was Singapore’s 13ha Bidadari Park where the 1.8ha Alkaff Lake can hold up to 40,000 cu m of stormwater. The park incorporates wetlands, swales, marshes and creeks that help capture and cleanse rainwater.
Redeveloping with resilience
The Sibu Cloudburst Masterplan also ties in with plans to redevelop Bukit Assek, an older part of the town where flood management is among the issues being addressed.
The project took another step forward in early 2026 when the Sarawak government announced that all three main components of the redevelopment masterplan had received approval from the Sarawak Planning Authority.
The redevelopment is expected to be carried out in four phases over approximately 15 years.
Unlike new townships where infrastructure and land uses can be planned together from the beginning, urban redevelopment must take into account existing buildings, roads, businesses and residents.
For Malaysia’s property industry, cloudburst planning also has implications for decisions before construction begins, including influences on how stormwater moves through a development.
Land allocated for landscaping could also provide temporary water storage where technically suitable.
However, developers must consider construction costs, land requirements, engineering specifications and maintenance responsibilities because poor maintenance, sediment accumulation or blocked outlets could undermine the effectiveness of even a well-designed system.
And of course, there are practical limitations to consider.
In densely built-up neighbourhoods, finding enough land for these features may be difficult, especially when existing roads and infrastructure leave little room for modifications.
For developers planning new townships, there is more room to experiment with different ideas and make flood management part of the overall township design.
Beyond flood protection
For homebuyers, the possibility of having to deal with frequent floods could make an otherwise attractive neighbourhood less appealing. Repeated flooding can also leave property owners facing hefty repair bills and disruptions to their daily routines.
Having proper flood mitigation measures in place is important, although landscaped water management features alone may be insufficient.
There is no single solution suitable for every Malaysian city. Urban flash floods, river overflows and coastal flooding involve different conditions, requiring combinations of engineering, land-use planning and environmental management.
The Sibu Cloudburst Masterplan shows how flood resilience can be considered alongside urban redevelopment ambitions. It all depends on the implementation, funding and the performance of the completed infrastructure.
As Malaysian cities continue to expand, the biggest challenge will be to ensure that development does not come at the expense of the natural systems that help manage water.