SHAH ALAM - Despite decades of flood mitigation efforts in Kuala Lumpur and Selangor, the Klang Valley remains vulnerable to increasingly intense rainfall events.
Experts spotlighted that flooding in the region is largely driven by a growing mismatch between ageing drainage infrastructure and changing weather patterns linked to climate change.
They add that long-term resilience will require stronger integration between urban planning and water management systems, alongside upgraded infrastructure and more climate-adaptive approaches to flood management.
Former Malaysian Water Partnership chairman Datuk Ir Nor Hisham Mohd Ghazali said the region’s drainage systems are no longer fully aligned with current rainfall conditions.
“Flooding in the Klang Valley is largely driven by drainage infrastructure that is unable to cope with the volume of runoff generated by increasingly frequent high-intensity rainfall events.
“These short-duration, heavy downpours have become more common over the years, while climate change has also contributed to longer drought periods.
“Because drainage systems are designed based on specific rainfall return periods, flooding occurs more often when actual rainfall exceeds those design thresholds,” he said in an interview with Sinar Daily.
Hisham said that major flood mitigation efforts have been implemented since the 1980s under the Kuala Lumpur Flood Mitigation (KLFM) programme.
The initiative was introduced to reduce flood risks in Kuala Lumpur and Selangor and has continued as part of long-term efforts to address flooding in these areas.
“It involved deepening and widening key rivers such as Sungai Klang, Sungai Gombak and Sungai Batu, as well as constructing infrastructure like the Batu Dam, Batu and Jinjang ponds and the Gombak diversion.
“Together with the Smart tunnel, these measures have helped prevent at least five major flood events in Kuala Lumpur, particularly those linked to monsoonal rainfall,” he added.
However, Hisham said that flash floods remain difficult to fully control due to their highly localised and fast-developing nature.
He explained that the Urban Stormwater Management Manual has introduced a “control at source” approach, requiring new developments to incorporate features such as detention ponds and green spaces to temporarily store runoff before it is released into rivers.
He also highlighted that ongoing rapid urbanisation continues to increase the risk and intensity of flash floods.
“Rapid urbanisation and land use change continue to intensify flood risks. Large-scale paving reduces natural absorption areas, while construction activities can temporarily worsen drainage conditions.
“Coordination challenges across different levels of government also affect flood management effectiveness. Flood prevention infrastructure is designed for specific risk levels; when events exceed those levels, the system can only reduce impact, not fully prevent flooding,” he mentioned.
Hisham said that despite existing constraints, the Klang Valley continues to show relatively strong resilience to flooding. He noted that, compared to many global cities, the region is still able to function even after rainfall events of about 60 to 70 millimetres over a three-hour period.
However, he stressed that future improvements should prioritise more integrated systems as well as measures that can deliver faster impact.
“Further improvements can be made by interconnecting detention ponds, developing offline ponds beside rivers and implementing targeted engineering solutions at known flash flood hotspots,” he suggested.
Water engineering expert from Universiti Putra Malaysia, Associate Professor Dr Syazwani Idrus, said that climate change has significantly changed rainfall patterns in Malaysia.
She explained that rainfall has become more volatile, with short but intense cloudbursts increasingly replacing the previously more predictable monsoon patterns.
According to her, this shift contributes to flooding in the Klang Valley, particularly in Shah Alam, where the situation is further worsened by a combination of structural weaknesses in flood management systems.
She added that extreme rainfall events, especially when combined with tidal conditions, further exacerbate the severity of flooding.
“In many cases, more than 60 mm of rain can fall within two hours, especially when heavy rainfall coincides with high tide in the Klang River, causing backflow in low-lying areas such as Sri Muda.
“Much of the drainage infrastructure was built based on data from the 1970s and 1980s, making it insufficient for current conditions. Rapid urbanisation has reduced natural absorption areas and increased surface runoff,” she told Sinar Daily.
She noted that the Klang River’s capacity has declined over time due to the accumulation of sediment and waste, which has reduced its ability to handle excess water.
At the same time, she added that mitigation efforts are being continuously carried out through infrastructure upgrades and the adoption of new technologies.
“Drainage systems are being enhanced, pumping stations upgraded and large-scale dredging projects are increasing river capacity. Digital twin technology is also being introduced to predict flood levels up to six hours in advance.
“The Sponge City concept is being applied through On-Site Detention tanks, requiring developers to retain rainwater within their properties,” she said.
Syazwani pointed out that cities around the world are increasingly adopting integrated water management approaches.
Urban centres such as Rotterdam, Singapore and Copenhagen have moved away from traditional concrete drainage systems and are now implementing more holistic strategies that combine water storage, green infrastructure and multifunctional urban spaces.
“These cities design spaces that can temporarily store water and use natural systems to slow runoff, rather than relying solely on rapid discharge systems.
“Malaysia is beginning to adopt similar concepts but still relies heavily on conventional infrastructure,” she said.
Experts agree that while Malaysia has invested heavily in flood mitigation infrastructure, rising rainfall intensity, urban expansion and ageing drainage systems continue to challenge long-term flood resilience in the Klang Valley.
A shift toward integrated, climate-adaptive urban water management is increasingly seen as necessary.