NST Leader: Highland Towers lessons - Better slope risk detection needed

TEN days before Dec 11, 1993, 175.5mm of rainfall poured over Ulu Kelang, with high-volume water coursing intensely down a hilly slope that housed three apartment buildings — Blocks 1, 2 and 3.

Built at the foot of a steep hillside, Block 1's natural drainage and stability were altered, slowly and steadily. The hillside slid progressively, in hindsight a retrogressive landslide, putting mounting pressure on Block 1's foundation and eventually crushing its retaining system, allowing a soil surge towards the building.

Ironically, Block 1's rail-pile foundations withheld the building's vertical load, but could not withstand the landslide's massive horizontal force. It was inevitable: heavy rain, inadequate drainage, a saturated and unstable slope, a progressive landslide and huge lateral soil pressure forced foundation piles to fail.

In just five minutes between 1.30pm and 1.35pm on that Saturday, Block 1 of the 12-storey, 52-unit Highland Towers collapsed, killing 48 residents. The victims had no inkling of the slow-moving catastrophe.

However, residents at Block D of the Bandar Damai Perdana flats in Cheras had a stark inkling, receiving at 9.03pm on Sept 22, 2026 an emergency call that a landslide had occurred nearby, caused by an underground water leak.

While the authorities didn't detect further soil movement, it was immaterial: the landslide was an extremely close call, prompting immediate evacuation — unlike the Highland Towers' victims.

Increasingly dense urban areas survive on a reactive approach whereby authorities investigate only after slopes fail, underground pipes burst, or buildings are evacuated.

As providence goes, this Cheras landslide fortuitously served as an opportunity to strengthen preventive slope monitoring, drainage maintenance, underground utility inspections and accountability for residential developments near vulnerable terrain.

High-rise buildings erected on slopes can have the best architecture and solid engineering but are almost always oblivious to hidden risks beneath urban development.

Landslides don't start with building failure: water movement, leaking pipes, drainage problems and soil instability progressively weaken slopes before any warning.

The last thing the authorities should do is treat this incident as an isolated landslip. If buildings are ageing, they need greater scrutiny.

Local authorities, water utility operators and technical agencies need clearer mechanisms to identify vulnerable slopes and underground infrastructure.

Regular inspections should focus not only on visible cracks or slope movement but also drainage, water leakage and other warning signs.

The Cheras episode highlights the importance of defining the responsibilities of residents' management, developers, utility providers and local authorities. These are the lessons and preventive measures to avoid another tragedy.