Mitigating flash floods in cities
THE flash flood that swept through Presint 11, Putrajaya on Dec 8 has raised questions about the resilience of urban infrastructure in the face of climate change.
Despite being a meticulously planned city with rainwater retention ponds and a systematic drainage system, Putrajaya could not escape the devastating effects of an hour-long downpour.
According to the Malaysian Meteorological Department, rainfall intensity has increased by 40% over the past five years with heavier and more frequent storms becoming the norm.
Driven by climate change, this alarming trend underscores the vulnerability of urbanised regions to extreme weather events. Global warming has significantly altered rainfall patterns as rising sea temperatures accelerate evaporation rates, producing more intense rainfall over shorter periods.
The Intergovernmental Panel on Climate Change (IPCC) has highlighted that tropical regions like Malaysia are particularly susceptible to such phenomena.
But heavy rainfall alone does not fully explain the recurring flash floods in urban areas. Uncontrolled urbanisation exacerbates the problem by replacing permeable natural surfaces with impermeable concrete, preventing rainwater from seeping into the ground.
Putrajaya, Malaysia’s administrative capital, was designed with significant green spaces, including 38% of its area dedicated to parks, lakes and wetlands, such as the 600ha man-made Putrajaya Lake, which helps moderate the local climate.
However, recent urbanisation and infrastructure development have strained its drainage system. In the past two decades, according to research by the Department of Irrigation and Drainage (DID), this urban sprawl has increased surface runoff by 35%, overwhelming its drainage system and causing flash floods.
The Town and Country Planning Act 1976 (Act 172) grants local authorities the power to regulate development and urges stricter control over land use activities.
The continuous disposal of waste into drains remains a major cause of flash floods too. Often caused by domestic waste generated by residents, clogged drains have severe impacts, especially in residential and commercial areas. Flash floods in cities like Ipoh have been characterised by dirty, oily floodwaters, raising public health concerns.
Moreover, ageing and inefficient drainage systems often fail to handle the increased water volume.
The Solid Waste Management and Public Cleansing Act 2007 (Act 672) emphasises the responsibility of local authorities in waste management. However, community-level compliance remains low, exacerbating the issue.
A holistic approach is essential to address these challenges. Urban planning must prioritise sustainable development, integrating green infrastructure like green roofs made from waterabsorbent materials, and drains and pedestrian pathways made with permeable pavements.
Cities like Singapore offer valuable lessons with initiatives such as the ABC Waters Program successfully incorporating water-absorbing features into urban designs.
Malaysia has made strides with its National Green Technology Policy (2009), but the implementation must expand to cover a wider range of urban areas.
Collaborative efforts among authorities, communities and the private sector is crucial. Strict development controls, regular maintenance of drainage systems, and the adoption of eco-friendly technologies are crucial in mitigating flash floods.
Equally important is public awareness. Educating communities about waste management and the impact of littering on drainage systems is vital for sustainable urban living.
Cities, including Putrajaya, must strive to balance modernisation with environmental stewardship to ensure long-term resilience against climate-related challenges. Flash floods are no longer isolated incidents but warning signs of a changing climate. With concerted efforts and innovative solutions, Malaysia can pave the way for a sustainable and resilient urban future.