By MOHD IZHAM BIN HASHIM
KOTA KINABALU: Increasingly unpredictable weather linked to climate change is intensifying flood risks in Sabah, but experts say the real problem lies closer to home—in how cities are designed and developed.
With rising temperatures, prolonged dry spells, and sudden bursts of heavy rainfall becoming more common, flooding is often seen as a direct consequence of global warming.
However, speakers at the panel discussion noted deeper structural weaknesses in urban planning may be amplifying the effects of climate change.
“The problem is not that we don’t have enough water. We have a lot of water,” said Datuk Ir. Ts. Dr. Amarjit Singh, former Director of the Sabah Water Department, noting that Sabah receives among the highest annual rainfall in Malaysia, estimated at around 2,700 millimetres annually.
“What has changed is how the water behaves when it enters the city,” he said, adding that urbanisation has reduced the ability of natural landscapes to absorb and store rainwater.
Dr Amarjit explained that rapid urban development has replaced permeable natural surfaces—once functioning like a sponge—with concrete and asphalt, preventing water from infiltrating the ground.
“With the expansion of development, water becomes surface runoff. It flows faster and in larger volumes into drainage systems that may not have been upgraded to handle it,” he said.
The panel discussion, titled “Urban Flood Resilience: Smart Solutions for Climate-Ready Cities,” was held in conjunction with the Plumbing Asia 2026 Conference & Expo, which carried the theme “Smart Water, Strong Nation, Sustainable Asia Future.” The forum was moderated by President of SME Bumiputera Chamber of Commerce Sabah (SBCCS), Benjamin Golimbi.
While drainage capacity is often blamed, Ir. Ts. Dr. Tom Ngui, committee member of the Institution of Engineers Malaysia (IEM) Sabah Branch, said the issue is far more complex than simply undersized drainage infrastructure.
“Urban flooding is usually not caused by a drain that is too small,” he said, attributing the problem instead to the loss of natural storage and conveyance systems.
Dr Tom noted that urban expansion has narrowed rivers, removed vegetation, and eliminated low-lying areas that once acted as natural retention basins.
“In many cases, we expect drainage systems to behave like full river systems, which they were never designed to do,” he said, describing flooding as “a failure of space rather than a failure of drains.”
He added that climate change is worsening the situation not necessarily by increasing total rainfall significantly, but by changing its intensity and timing.
“The real engineering challenge is not simply building bigger drains, but restoring the city’s ability to slow, store, convey and safely reroute excess stormwater during extreme events,” he said.
Dr Tom said rainfall patterns are becoming more erratic, with longer dry periods followed by short, intense storms that overwhelm urban systems.
“Flood risk today is driven by extreme peaks, not averages,” he said. “We now see intense rainfall within a short period, which places sudden pressure on drains and rivers.”
For coastal cities like Kota Kinabalu, he added, the challenge is further compounded by rising sea levels and tidal influences.
During high tide events, stormwater is unable to discharge efficiently into the sea, causing backflow into drainage systems and increasing flood risk.
“This is what we call compound flooding, where rainfall, river levels and tidal conditions interact at the same time,” he explained.
Dr Amarjit also highlighted that ongoing development activities, particularly hillside cutting, are worsening flood risks.
Large-scale clearing of hills for urban expansion removes vegetation that would normally slow runoff, while exposing loose soil that is easily washed into rivers and drainage systems during heavy rain.
“When hills are cut and vegetation is removed, water flows down much faster, carrying sediment into rivers and drains,” he said. “This reduces the capacity of the system and increases the likelihood of flooding.”
Such practices, increasingly visible across Kota Kinabalu and other parts of Sabah, not only accelerate runoff but also contribute to long-term degradation of drainage infrastructure through sediment build-up.
Experts noted that many existing drainage systems were designed based on earlier development conditions and may no longer be sufficient to handle the increased volume and speed of runoff driven by urban growth.
Meanwhile, Ir. Lee Tet Fon, Past Chairman of the Sabah Branch of the Institution of Engineers Malaysia (IEM), said the combined pressures of climate change, rising sea levels, and rapid land-use change are reshaping flood risk in urban areas.
Despite growing focus on climate change, the panel agreed that addressing flooding requires more than adapting to changing weather patterns alone.
“Unpredictable rainfall is forcing a shift from traditional ‘drain-and-dispose’ systems to redesigned urban spaces that absorb, store and slow down water like a natural sponge,” Dr Lee said.
From left to right are Benjamin, Dr Amarjit, Dr Tom and lr. Lee.
