By Teh Eng Hock
There was much ado over the recent flooding along Persiaran Kewajipan in USJ, even though the flash flood lasted only 15 to 20 minutes and the road remained passable to traffic throughout.
But for the authorities to dismiss residents’ concerns as an overreaction would be a mistake.
As the water levels crept upwards, many residents were transported back to the traumatic floods of 2019. Several residents reported that while floodwaters did not enter their homes this time, they came uncomfortably close. Imagine watching the water rise minute by minute, unsure whether your home would once again be engulfed by floodwater.
To its credit, MBSJ had undertaken a flood mitigation project, including a 750.6-cubic-metre on-site detention facility aimed at addressing persistent flooding in the area. Subang Jaya assemblywoman Michelle Ng said the investment “fulfilled its immediate containment role and averted severe property damage”. In short, the project appears to have played a significant role in preventing floodwaters from entering nearby homes during the latest incident.
Nevertheless, this is hardly the time to pat ourselves on the back and declare victory.
Before the next episode of “unprecedented” or “extreme” rainfall arrives, we must look beyond short-term mitigation and focus on long-term resilience. Extreme weather events are becoming more frequent and more intense. If climate change is indeed the new normal, then our drainage and retention systems must be designed with sufficient buffer capacity to cope with conditions that were once considered exceptional.
Seeking a technical perspective, I asked a former city councillor, who is also a civil engineer specialising in flood mitigation, for his opinion.
His response was simple, though by no means easy: increase the capacity of the Klang River through infrastructure such as bunds and other flood management measures.
“All the rainwater eventually flows into the Klang River. And when the Klang River itself is at or near full capacity, what happens then?” he said.
A little Flood Mitigation 101 may be useful here.
Even if the Klang River does not overflow its banks, elevated river levels can severely impair the effectiveness of the internal drainage system. When river levels are high, they create a hydraulic barrier at the discharge points where Subang Jaya’s drains empty into the river.
Instead of flowing out smoothly, stormwater runoff encounters a wall of water downstream. The result is a backflow effect. Water accumulates in the drains, backs up through the system and eventually spills onto the streets, creating flash floods even when the river itself remains within its banks.
Residents do not need engineering qualifications to notice another worrying trend. Subang Jaya continues to develop at a rapid pace, bringing with it more concrete, asphalt and rooftops, while reducing the amount of permeable land available to absorb rainwater.
During heavy storms, natural ground that once absorbed rainfall is replaced by hard surfaces that channel water rapidly downhill. In effect, urban development creates a giant speedway for rainwater, directing it towards lower-lying areas such as Persiaran Kewajipan and parts of USJ 1, both of which sit close to the Klang River.
This raises an important question: have town planners fully accounted for the cumulative impact of new developments?
The drainage system serving a particular development in USJ 7 or USJ 14 may well meet all regulatory requirements within its boundaries. But have planners sufficiently considered the additional runoff generated from higher-ground neighbourhoods such as USJ 5 and USJ 11? Water, after all, does not respect planning boundaries. What happens upstream inevitably affects those living downstream.
Another observation frequently raised by residents’ concerns road cleaners who sweep or blow leaves into roadside drains. The perception is that this contributes to clogged drains and worsening floods.
Personally, I believe non-organic litter such as plastic packaging, food containers and discarded rubbish pose a far greater threat to drainage systems. On that front, stronger enforcement against littering would certainly be welcomed.
As for leaves, I suspect their contribution to flooding is negligible in comparison to larger structural issues within the drainage network. That said, sweeping leaves into drains is neither proper nor professional. I am certain it runs contrary to KDEB Waste Management’s work protocols. Beyond the operational issue itself, the practice damages the company’s corporate reputation. Management should take firm steps to improve supervision and ensure it is brought to an end.
The recent flood may not have caused major losses, and for that we should be grateful. But gratitude must not breed complacency.
The fact that residents were once again anxiously monitoring rising water levels should concern everyone. A flood does not have to enter homes to expose weaknesses in our flood management system. Sometimes, a near miss is warning enough.
What we need is not another round of explanations after every heavy downpour. We need a culture shift. Flood resilience must become a non-negotiable priority in how we plan developments, maintain infrastructure, enforce regulations and allocate public funds.
Too often, we celebrate projects once they are completed and move on, only to be reminded by the next storm that the job is far from finished. Flood mitigation is not a one-off achievement. It is a continuous commitment that demands vigilance, accountability and the courage to make difficult decisions before a crisis forces our hand.
The waters along Persiaran Kewajipan may have receded within minutes. Our willingness to confront uncomfortable truths should not recede with them.
Because when the next major flood comes, residents will not remember the explanations, the press statements or the assurances given after the fact. They will remember whether those entrusted with managing our city took action when the warning signs were clear.
